New guy has aux fan woes

[Jay 535i]

Hi all. I'm new here, and new to BMW-dom.

I've just inherited my father's 1990 535i, with an auto tranny and 220,000km on the clock (about 140,000mi).

I'll save the story for another time and cut right to the chase.

The aux fan never comes on. Never. The A/C also does not work. The car overheats any time the speed drops below 40mph, making the car undriveable.

Hoses, coolant and thermostat are new. Radiator is not OEM, but looks like a quality item in good shape. Probably replaced by a previous owner.

Now, my questions:

1. Could the aux fan problem be the reason why the A/C doesn't work, or is it wishful thinking that fixing the aux fan will restore the A/C?

2. Is the aux fan failure the cause of the overheating problem? The rest of the cooling system seems fine.

3. What are the steps for diagnosing the cause of the aux fan failure? I've read about aux fan switches and resistors, but can't figure out where they are or what they look like. I've ordered a Bentley manual but it hasn't arrived yet.

Any help is greatly appreciated. Thanks.

[dacoyote]

Hi all. I'm new here, and new to BMW-dom.

I've just inherited my father's 1990 535i, with an auto tranny and 220,000km on the clock (about 140,000mi).

I'll save the story for another time and cut right to the chase.

The aux fan never comes on. Never. The A/C also does not work. The car overheats any time the speed drops below 40mph, making the car undriveable.

Hoses, coolant and thermostat are new. Radiator is not OEM, but looks like a quality item in good shape. Probably replaced by a previous owner.

Now, my questions:

1. Could the aux fan problem be the reason why the A/C doesn't work, or is it wishful thinking that fixing the aux fan will restore the A/C?

2. Is the aux fan failure the cause of the overheating problem? The rest of the cooling system seems fine.

3. What are the steps for diagnosing the cause of the aux fan failure? I've read about aux fan switches and resistors, but can't figure out where they are or what they look like. I've ordered a Bentley manual but it hasn't arrived yet.

Any help is greatly appreciated. Thanks.

Has the car had the newer style metal water pump installed?

When was the last time the cars coolant was flushed?

-Charles

[Jay 535i]

Has the car had the newer style metal water pump installed?

Huh? Didn't know there was such a thing. How would I know?


When was the last time the cars coolant was flushed?

Dunno exactly, although the thermostat was replaced last month. Would that have necessitated a coolant flush? The coolant looks a-ok.

I should add that this problem surfaced about six months ago, and it's been sufacing again and again despite my mechanic's efforts. Since the aux fan does not work at all, I'm likely to suspect it as the cause of the problem. But what do I know?

Thanks for the help.

[uscharalph]

Hi all. I'm new here, and new to BMW-dom.

I've just inherited my father's 1990 535i, with an auto tranny and 220,000km on the clock (about 140,000mi).

I'll save the story for another time and cut right to the chase.

The aux fan never comes on. Never. The A/C also does not work. The car overheats any time the speed drops below 40mph, making the car undriveable.

Hoses, coolant and thermostat are new. Radiator is not OEM, but looks like a quality item in good shape. Probably replaced by a previous owner.

Now, my questions:

1. Could the aux fan problem be the reason why the A/C doesn't work, or is it wishful thinking that fixing the aux fan will restore the A/C?

2. Is the aux fan failure the cause of the overheating problem? The rest of the cooling system seems fine.

3. What are the steps for diagnosing the cause of the aux fan failure? I've read about aux fan switches and resistors, but can't figure out where they are or what they look like. I've ordered a Bentley manual but it hasn't arrived yet.

Any help is greatly appreciated. Thanks.
First of all, the aux fan should come on when the temp gauge hit 3/4 or when the a/c goes on. Since the a/c doesn't work, does the gauge reach the 3/4 mark or higher when it overheats?

[uscharalph]

Huh? Didn't know there was such a thing. How would I know?



Dunno exactly, although the thermostat was replaced last month. Would that have necessitated a coolant flush? The coolant looks a-ok.

I should add that this problem surfaced about six months ago, and it's been sufacing again and again despite my mechanic's efforts. Since the aux fan does not work at all, I'm likely to suspect it as the cause of the problem. But what do I know?

Thanks for the help.
If you have the PO's repair records, you know when the water pump was replaced.

Does your car have a timing belt, which needs to be replaced at regular intervals 50,000-60,000 miles? If it has that belt and you don't have repair records I'd be worried about that. The good news is it's in the same area as the water pump and you can replace both at the same time.

[Rory]

Hi all. I'm new here, and new to BMW-dom.

I've just inherited my father's 1990 535i, with an auto tranny and 220,000km on the clock (about 140,000mi).

I'll save the story for another time and cut right to the chase.

The aux fan never comes on. Never. The A/C also does not work. The car overheats any time the speed drops below 40mph, making the car undriveable.

Hoses, coolant and thermostat are new. Radiator is not OEM, but looks like a quality item in good shape. Probably replaced by a previous owner.
Welcome!! Enjoy the new ride.



Now, my questions:

1. Could the aux fan problem be the reason why the A/C doesn't work, or is it wishful thinking that fixing the aux fan will restore the A/C?
[/QUOTE}
Yes, it is very possible. Also check the fuse box, if the resistor is bad the fuse is probably blown.

Check the following link for more info:
http://www.nmia.com/~dgnrg/page_20.htm

[QUOTE=jaylebo]
2. Is the aux fan failure the cause of the overheating problem? The rest of the cooling system seems fine.
Note likely. That sounds to me like the H2O pump may not be working properly. Only way to know for sure is to pull the pump. When is the last time your records indicate it was replaced? Most professionals are recommending replacement of the pump at 60K intervals now as a preventative measure.



3. What are the steps for diagnosing the cause of the aux fan failure? I've read about aux fan switches and resistors, but can't figure out where they are or what they look like. I've ordered a Bentley manual but it hasn't arrived yet.

Any help is greatly appreciated. Thanks.See the link above for everything you would ever want to know.

Good Luck,
Rory

[Adnan]

Hi,

Aux fan aside, it sounds to me like your fan clutch needs replacement. This is the viscous coupling that drives the primary fan. These do fail pretty regularly and with the mileage and age you have, it's a pretty good bet it's time.

Next step is to check the temperature sensors that control the aux fan. There should be two speeds, so check the wiring diagram. You can connect the fan directly to power to see if it comes on; this would confirm whether the fan itself is okay or not.

Regards,
Adnan

[Jay 535i]

Thanks for all the replies. Here're the answeres to all the questions.


First of all, the aux fan should come on when the temp gauge hit 3/4 or when the a/c goes on. Since the a/c doesn't work, does the gauge reach the 3/4 mark or higher when it overheats?

Oh yeah, it'll go into the red.


Does your car have a timing belt, which needs to be replaced at regular intervals 50,000-60,000 miles? If it has that belt and you don't have repair records I'd be worried about that. The good news is it's in the same area as the water pump and you can replace both at the same time.

There is a belt, but I thought these cars had timing chains. There are no records, so I'd assume the worst. But I want to tackle the most likely culprits first, and since the aux fan isn't working it seems reasonable to start there. Doesn't it?

As far as I can tell, all underhood fuses are okay. Haven't looked under the rear seats.

Thanks for the tips, Rory. Water pump may not be that old. Unfortunately, my father wasn't the kind to keep records, but I have a vague recollection of him replacing that. His local mechanic is an honest and competent guy, but not a BMW specialist. That's why I'm inclinded to suspect that he totally overlooked the aux fan as a possible culprit, as it's damn near invisible to the uninitiated.

Adnan, thanks. I've read a bit about the clutch fan in my search that brought me to this site, and I don't see any evidence of it needing replacing. The fan blows strong at all engine speeds. Can you recommend some sort of test?


Next step is to check the temperature sensors that control the aux fan. There should be two speeds, so check the wiring diagram. You can connect the fan directly to power to see if it comes on; this would confirm whether the fan itself is okay or not.

That's a little over my head. If you can describe exactly what to do, I'm sure I can do it, but I don't have a wiring diagram (yet -- Bentley is on the way), nor can I read one.

Many thanks for all the help. Please keep it coming.

[winfred]

unless it's leaking or making a noise the pump is fine, m30s didn't have the plastic impeller, id bet whats happening is the bleeder line that goes from the left upper side of the radiator to the coolent tank is clogged somewhere, usually it's at the coolent tank end, when this line stops flowing the system can get airlocked

[Kalevera]

Huh? Didn't know there was such a thing. How would I know?



Dunno exactly, although the thermostat was replaced last month. Would that have necessitated a coolant flush? The coolant looks a-ok.

I should add that this problem surfaced about six months ago, and it's been sufacing again and again despite my mechanic's efforts. Since the aux fan does not work at all, I'm likely to suspect it as the cause of the problem. But what do I know?

Thanks for the help.
The M30 never came with a plastic water pump impeller, to my knowledge. All are metal.

Who installed the thermostat? My guess is that the rubber O ring wasn't inserted correctly, and the tstat is stuck. The car may cool down below the 1/4 tick mark under way if this is the case. The rubber O ring goes behind the tstat in the housing, fitting right up against the thermostat cover. Here's a pic of how it orients on the tstat itself:

http://img.photobucket.com/albums/v736/suzpectx/tstat.jpg

...where the end in the photo is the cover side. Correct fitment is necessary: the tstat housing coolant passages are altered depending on what the tstat is doing.

best, whit

EDIT: also note that the gasket shown in the picture isn't the O ring....the O ring should be installed, not the gasket.

[Jay 535i]

unless it's leaking or making a noise the pump is fine, m30s didn't have the plastic impeller, id bet whats happening is the bleeder line that goes from the left upper side of the radiator to the coolent tank is clogged somewhere, usually it's at the coolent tank end, when this line stops flowing the system can get airlocked

How could I check this out? I find it odd that coolant comes spewing out the cap when I unscrew it, even with the engine ice cold. Does that indicate anything?

Lowell, thanks for the tips but I don't see any signs of a failing tstat. The engine temp never drops below midway once warmed up, but does go well beyond that if I don't keep moving quickly.

Rory, thanks again for the link. Thanks to it, I may have found something. I noticed on the label inside my fuse box that fuse #25 (one of two for the aux fan) ought to be good for 30 amps. The fuse I pulled has a 15 stamped on it, and it's blown. I'll replace it tomorrow. Hopefully that'll be the end of the overheating issue, or at the very least get the aux fan working properly.

[winfred]

one way is with the cap off start it and look for coolent circulating when you rev it a little, crud from the cooling system plugs up the tube and airlocks the system, this could be your burping when removing the cap cold too


How could I check this out? I find it odd that coolant comes spewing out the cap when I unscrew it, even with the engine ice cold. Does that indicate anything?

[Kalevera]

How could I check this out? I find it odd that coolant comes spewing out the cap when I unscrew it, even with the engine ice cold. Does that indicate anything?

Lowell, thanks for the tips but I don't see any signs of a failing tstat. The engine temp never drops below midway once warmed up, but does go well beyond that if I don't keep moving quickly.

Rory, thanks again for the link. Thanks to it, I may have found something. I noticed on the label inside my fuse box that fuse #25 (one of two for the aux fan) ought to be good for 30 amps. The fuse I pulled has a 15 stamped on it, and it's blown. I'll replace it tomorrow. Hopefully that'll be the end of the overheating issue, or at the very least get the aux fan working properly.
That's exactly my point: if the tstat is stuck at a certain open position, it will be fine above a certain speed, as the antifreeze going through the radiator will be sufficiently cooled due to air volume to keep things "normal". As the speed drops (stop and go, whatever), the tstat is unable to open further to compensate with flow for what air volume and cooler antifreeze do at higher speeds.

Unless you're in a very hot climate, the aux fan won't matter. The temperature gauge in our cars has a lot of leeway dialed into it. A non-operating aux fan would, on a hot day, bump the temp gauge about a tick mark above 12, if that, with an 80 degree tstat.

best, whit

[632 Regal]

clutch fan clutch fan...when its hot and its warm outside and you take off it should have that infamous "school bus" sound if the clutch fan is good.

The coolant shouldnt spew out when cold either...

[Jay 535i]

Winfred, thanks, I'll do that.

Lowell, thanks, if I haven't solved this problem by the time my Bentley manual arrives from Amazon, I'll pop in a new thermostat and be sure to do it right.

632 Regal, is there a test I can do for the clutch fan besides the noise you mention? I read someone suggest you try to stop it turning, but I'm not sure how to do that safely. I'm pretty sure my car doesn't sound like a school bus, but I'm not sure it should. Please explain.

How does a faulty clutch fan cause an overheat? Is it because the fan's not moving fast enough?

Good to know that my coolant spewing out when cold isn't normal. But what's the cause? I'll check for a blocked bleeder line, but what else could it be? The car is fine at high speeds. Isn't that evidence that coolant is flowing, and there's no airlock or obstruction?

[winfred]

worst case for the pressure is the head gasket, it's not uncommon for 535 m30 motors to corrode the back corner of the head gasket due to under mantance of the cooling system


Good to know that my coolant spewing out when cold isn't normal. But what's the cause? I'll check for a blocked bleeder line, but what else could it be? The car is fine at high speeds. Isn't that evidence that coolant is flowing, and there's no airlock or obstruction?

[Kalevera]

Actually, the more I think about it, the more I agree with Winfred's idea. A partially clogged pisser would do it, which would explain why consistently higher RPMs are necessary to keep it cool.

The fan blades can be grabbed at idle...I'd wear a glove, but I've seen it done with bare hands.

best, whit

[Jay 535i]

Actually, the more I think about it, the more I agree with Winfred's idea. A partially clogged pisser would do it, which would explain why consistently higher RPMs are necessary to keep it cool.

Actually, the car stays cooler with lower RPMs, but high speed. I'll check that hose, though.


The fan blades can be grabbed at idle...I'd wear a glove, but I've seen it done with bare hands.

And what will I feel if the clutch is bad? And will I keep my fingers if the clutch is good?

[632 Regal]

grabbing a spinning fan? Somehow that brings back painful memories and a permanently numbed finger...

When you take off with the windows open you WILL hear the fan sound if the clutch is good.

[Jay 535i]

worst case for the pressure is the head gasket, it's not uncommon for 535 m30 motors to corrode the back corner of the head gasket due to under mantance of the cooling system

Sorry, I don't get how a bad head gasket would increase the pressure like that. Can you please explain?

The oil is clean, so there's no coolant in it, if that tells you anything.

[Kalevera]

Actually, the car stays cooler with lower RPMs, but high speed. I'll check that hose, though.



And what will I feel if the clutch is bad? And will I keep my fingers if the clutch is good?


...That still makes me think the tstat is stuck half open, or is only able to open half way. Given that there's no other problem (ie., headgasket), I wouldn't be surprised if the tstat is operable yet somehow just stuck in the wrong position. Either way, I'm sure you'll figure it out. Not much coolant is lost when the tstat cover is removed with the front of the car up in the air, so it's a quick and easy thing to check. Spewing coolant out of the expansion tank when the car is cold sounds ominous, though. It's only supposed to do that when really warm and under pressure. Any other signs of a blown head gasket?

The fan blades can be held at idle...~800 rpm. I've only seen it done; never done it myself -- what's the point? you can just turn off the car and get the same result. When releasing the blades, the clutch should immediately spin up and produce a considerable flow (just as it should when starting the car). The quickest and easiest way to test the fan clutch that I know of is to get the car warm and give it a quick rev, or take it for a drive and do a little hard acceleration from a stop....like Jeff said...and listen for the whoosh. It can also be done under hood, but since the car's a non-US model, it probably has EML, so someone has to tap the gas pedal. There's also the shutoff test, but I've seen instances of a walking VC that still did the job fine otherwise. Also...try not to rev it up too much in park or neutral, it'll eat the transmission.

Good luck!

best, whit

[Kalevera]

Sorry, I don't get how a bad head gasket would increase the pressure like that. Can you please explain?

The oil is clean, so there's no coolant in it, if that tells you anything.
Yup, exhaust gasses that should be exiting the motor through the headers get pressed past the remnants of a head gasket and into the water jacket. The cooling system is designed to self bleed any air, but a full load of exhaust gasses overloads the system and the hoses get rock hard to the touch.

best, whit

[Jay 535i]

Yup, exhaust gasses that should be exiting the motor through the headers get pressed past the remnants of a head gasket and into the water jacket. The cooling system is designed to self bleed any air, but a full load of exhaust gasses overloads the system and the hoses get rock hard to the touch.

best, whit

Cheers. The hoses aren't rock hard, as you describe. Also, if this were happening and exhaust gasses were getting into the water jackets, doesn't it also follow that coolant would get into the oil? The oil is spotlessly clean.

I'm anxious to check out the thermostat. Will do when the Bentley manual arrives from Amazon.

Gonna go try to produce that 'school bus' sound now. If I can't do it, then I guess the fan clutch is bad.

Thanks for all the help. I'd be lost without it. I'll post an update soon.

[dacoyote]

The M30 never came with a plastic water pump impeller, to my knowledge. All are metal.

Who installed the thermostat? My guess is that the rubber O ring wasn't inserted correctly, and the tstat is stuck. The car may cool down below the 1/4 tick mark under way if this is the case. The rubber O ring goes behind the tstat in the housing, fitting right up against the thermostat cover. Here's a pic of how it orients on the tstat itself:

http://img.photobucket.com/albums/v736/suzpectx/tstat.jpg

...where the end in the photo is the cover side. Correct fitment is necessary: the tstat housing coolant passages are altered depending on what the tstat is doing.

best, whit

EDIT: also note that the gasket shown in the picture isn't the O ring....the O ring should be installed, not the gasket.


This is why I like Whit, he knows what is in all the cars, and has even seen/worked a m30... as compared to me where all I got is my m50TU.. and lots of time...

-Charles

[Jay 535i]

It's just come to my attention that the coolant ought to be blue. Mine's green. Problem?

[dacoyote]

http://www.bimmer.info/forum/showthread.php?t=12775

We are in the middle of debatting it.

I think you should use the right stuff... as long as the right stuff isn't dexacool....

-Charles

[Jay 535i]

Thanks all, again, so much for helping out. Here's an update.

First, my Bentley manual arrived, so the following was done with help from that.

I popped the hood and removed the coolant cap. As usual, despite the car being cold, about 200mL of coolant came out and landed on the ground. The coolant level remained almost right up to the cap's threads.

I started the car, and it seemed to me as though coolant was indeed flowing in and out of the overflow resevoir. As per the manual, I waited a couple of minutes and then felt the radiator top hose. It was cold, indicating a closed thermostat. Squeezing the hose changed the level in the overflow tank, which I take to mean there are no obstructions.

While waiting for the engine to warm up, I did the 'school bus' test on the fan clutch, and I think it passes. It does sound a bit like a school bus when revved, and, with the engine off, it can be turned easily but not freewheeled, which Bentley says is good.

As the needle approached the midway mark on the temp guage, coolant suddenly started spewing out of the open filler. Quite a lot, really -- maybe close to a litre. I shut the car off, replaced the cap, and restarted the car. Now the radiator top hose felt firm (but not hard) and hot, indicating an open thermostat, according to Bentley.

I take it that the major belching was caused, somehow, by the opening of the thermostat. Not sure what that indicates, or if it's normal.

I replaced the burned out aux fan fuse, with no change. The aux fan still will not come on regardless of circumstances. I've tried removing the aux fan switch to try the jumper trick, but it won't come off and I'm worried about breaking it, so I've left it for now. How do you get it off? Pull? Twist? Sing to it? I don't have the equipment or the know-how to test the aux fan relays.

In time, the temp needle began creeping toward the red, which is when I shut it off.

So, it seems to me that:

1. The fan clutch is okay.
2. The thermostat is okay.
3. The coolant is flowing.

Are those reasonable conclusions? What does that leave as the possible cause of the overheating problem? Bentley says bad/clogged rad, but I don't think that's it.

I am still concerned about the aux fan not working, although some people here are suggesting that the engine temp should be fine without it. I might have to leave it to a pro to sort that one out.

On the bright side, I managed to remove the awful tint job, and playing with the fuses has mysteriously brought my underhood lamp back to life. So it wasn't a total loss. ;)

Please help!

[dacoyote]

As the needle approached the midway mark on the temp guage, coolant suddenly started spewing out of the open filler. Quite a lot, really -- maybe close to a litre. I shut the car off, replaced the cap, and restarted the car. Now the radiator top hose felt firm (but not hard) and hot, indicating an open thermostat, according to Bentley.

I take it that the major belching was caused, somehow, by the opening of the thermostat. Not sure what that indicates, or if it's normal.



That would scream clogged / slow flow radatior to me, (however my standard bmw disclaimer applies) Does the lower hose warm up?

-Charles

[Jay 535i]

That would scream clogged / slow flow radatior to me, (however my standard bmw disclaimer applies) Does the lower hose warm up?

-Charles

There's a lower hose? I told you I'm new at this.

I'll check it out later and let you know.

So you're thinking the rad is the problem, then? Anyone second that emotion?

[dacoyote]

There's a lower hose? I told you I'm new at this.

I'll check it out later and let you know.

So you're thinking the rad is the problem, then? Anyone second that emotion?

There should be a second hose on the other side going back into the engine, I always call it the lower hose as in it is quite often lower on the other side of the rad. (normally passanger side)

Now I will have to go check and see if it really lower on the bmw's

-Charles

[BennyM]

I don't think it's the aux fan that's causing an overheat. I've been running without a functioning aux fan for a couple years and the temp gauge has never gone past the halfway mark. I have a newer 525i, but I can't imagine the 535i's engine running that much hotter. The aux fan is required for AC to function properly though. I can only safely run my AC at highway speed. If only those fans weren't so friggin expensive!

Secondly, the 535i has a timing BELT. Engines that came later had chains.

hope that helps,
BennyM




Thanks for all the replies. Here're the answeres to all the questions.



Oh yeah, it'll go into the red.



There is a belt, but I thought these cars had timing chains. There are no records, so I'd assume the worst. But I want to tackle the most likely culprits first, and since the aux fan isn't working it seems reasonable to start there. Doesn't it?

As far as I can tell, all underhood fuses are okay. Haven't looked under the rear seats.

Thanks for the tips, Rory. Water pump may not be that old. Unfortunately, my father wasn't the kind to keep records, but I have a vague recollection of him replacing that. His local mechanic is an honest and competent guy, but not a BMW specialist. That's why I'm inclinded to suspect that he totally overlooked the aux fan as a possible culprit, as it's damn near invisible to the uninitiated.

Adnan, thanks. I've read a bit about the clutch fan in my search that brought me to this site, and I don't see any evidence of it needing replacing. The fan blows strong at all engine speeds. Can you recommend some sort of test?



That's a little over my head. If you can describe exactly what to do, I'm sure I can do it, but I don't have a wiring diagram (yet -- Bentley is on the way), nor can I read one.

Many thanks for all the help. Please keep it coming.

[winfred]

the 535 like every other m30 motor has a timing chain, the only american speq bimmer motor that had a rubber band was the m20 82-88 528e and 84-92 325 e/i and 89-90 525


Secondly, the 535i has a timing BELT. Engines that came later had chains. BennyM

[Kalevera]

Jay --

Let's see...Yes, it's a bad idea to leave the cap off of the expansion tank as the motor comes to temperature. But, it should start spewing coolant when turned OFF hot and without a cap on, not while running. Correct coolant return is depicted in a picture on Don Gale's page regarding bleeding the M30 (http://www.nmia.org/~dgnrg/) -- a stream should come from the return line when the motor is revved.

If the head gasket is gone: the only way to really know is to do a few tests -- cooling system pressure test is a good precursor, then a compression test on each cylinder. White smoke out the tail pipe / oil in coolant / coolant in oil (froth/chocolate milk) all show up as signs of it, but they can still not be present with a cooked gasket.

It could be a shitty coolant problem. Unlikely, but seeing as the car probably has prestone in it, it might be smart to change it with 50/50 Zerex G05 and distilled water. Or test the coolant currently in the car.

Having a hot upper radiator hose really doesn't tell much of anything. If the thermostat is doing what I think it's doing, the upper radiator hose will be hot, so will the first half of the radiator where the URH meets it. The other side will be "cold", so will the lower radiator hose. When things are flowing correctly, the lower radiator hose is "warm", the URH is "hot", and the radiator is a spectrum of the two.

I'm not sure that there's anything that can be said to allay your fears regarding the aux fan. It just isn't necessary for anything other than extreme overheating conditions and the operation of the A/C. The plastic connector (usually engine harness side) can shatter. Be careful and work at it -- it pulls straight out, no technique to it.

In terms of its operation: can the thing be physically turned? More of an E30/E28 and earlier problem, but the motors lock up very easily, especially with a little salt. Magnets will come unfastened and get stuck to the commutator.


best, whit

[Jay 535i]

Jay --

Let's see...Yes, it's a bad idea to leave the cap off of the expansion tank as the motor comes to temperature. But, it should start spewing coolant when turned OFF hot and without a cap on, not while running. Correct coolant return is depicted in a picture on Don Gale's page regarding bleeding the M30 (http://www.nmia.org/~dgnrg/) -- a stream should come from the return line when the motor is revved.

If the head gasket is gone: the only way to really know is to do a few tests -- cooling system pressure test is a good precursor, then a compression test on each cylinder. White smoke out the tail pipe / oil in coolant / coolant in oil (froth/chocolate milk) all show up as signs of it, but they can still not be present with a cooked gasket.

It could be a shitty coolant problem. Unlikely, but seeing as the car probably has prestone in it, it might be smart to change it with 50/50 Zerex G05 and distilled water. Or test the coolant currently in the car.

Having a hot upper radiator hose really doesn't tell much of anything. If the thermostat is doing what I think it's doing, the upper radiator hose will be hot, so will the first half of the radiator where the URH meets it. The other side will be "cold", so will the lower radiator hose. When things are flowing correctly, the lower radiator hose is "warm", the URH is "hot", and the radiator is a spectrum of the two.

I'm not sure that there's anything that can be said to allay your fears regarding the aux fan. It just isn't necessary for anything other than extreme overheating conditions and the operation of the A/C. The plastic connector (usually engine harness side) can shatter. Be careful and work at it -- it pulls straight out, no technique to it.

In terms of its operation: can the thing be physically turned? More of an E30/E28 and earlier problem, but the motors lock up very easily, especially with a little salt. Magnets will come unfastened and get stuck to the commutator.


best, whit

Thanks for that.

The aux fan does spin freely. In any case, you've convinced me that the aux fan failure isn't the cause of the overheating. :)

I guess I'll have to take the car to a pro to have those pressure checks done. At least I can tell them where to start.

I'll have another go tomorrow and check the temp of the lower rad hose and get back to you.

When running the engine with the coolant cap off, I didn't really see the flow that I've seen in other cars. I don't know what's normal for this car, though. But there wasn't much of a current, from what I could see. Maybe it is gummed up somewhere. Any sort of test I can do at home for this? Otherwise I'll take it to a non-dealer BMW specialist I found in the Toronto Yellow Pages, unless someone knows someone in the area.

The link you posted is dead.

Thanks again.

[Kalevera]

Sorry....that's:

http://www.nmia.com/~dgnrg/page_2.htm

I, for some reason, always want to stick a .org in that URL. It's a com.

Anyway... Toronto. Take the car to Bruno. Everybody else doesn't know what they're talking about.

A length of weed whip line will clear the return line in a few seconds.

best, whit

[winfred]

it should be pissing pretty good through that small hole that's hooked to the line from the radiator on a rev

[Jay 535i]

Sorry....that's:

http://www.nmia.com/~dgnrg/page_2.htm

I, for some reason, always want to stick a .org in that URL. It's a com.

Anyway... Toronto. Take the car to Bruno. Everybody else doesn't know what they're talking about.

A length of weed whip line will clear the return line in a few seconds.

best, whit

Who's Bruno? And where?

What's weed whip line? You mean that white line on a weed wacker? Just push it in there, or what?

Winfred, it's hard to know what's coming out of there because the coolant level is higher than the top of the hole. I don't see a lot of action in there. Tomorrow I'll take a picture and post it. Meanwhile, keep the ideas comin'.

[Kalevera]

Bruno is the guy who wrote http://www.bmwe34.net. He's in toronto and knows everything about the E34.

Weed whip line. A weed whacker/weed whip/weed eater (TM)...whatever you want to call it...is a device with a small, usually two stroke motor on it that is used to trim grass areas or edges in a lawn that can't be cut with a conventional mower. Such devices mostly use a spool of hard plastic "line" to do the cutting (versus a steel blade). The line is long and flexible, yet taut. A section of this stuff can be run through the return line from the rubber ? shaped part at the radiator.

Weed whip line in action:

http://i.walmart.com/i/p/00/02/70/05/90/0002700590232_AV2_500X500.jpg

The actual stuff:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7705040835&category=71278&ssPageName=WDVW&rd=1

also available....anywhere :D


best, whit

[Jay 535i]

Bruno is the guy who wrote http://www.bmwe34.net. He's in toronto and knows everything about the E34.

Dude! What luck! I'll get in touch with him. Thanks.


Weed whip line. A weed whacker/weed whip/weed eater (TM)...whatever you want to call it...is a device with a small, usually two stroke motor on it that is used to trim grass areas or edges in a lawn that can't be cut with a conventional mower. Such devices mostly use a spool of hard plastic "line" to do the cutting (versus a steel blade). The line is long and flexible, yet taut. A section of this stuff can be run through the return line from the rubber ? shaped part at the radiator..

Gotcha. Thanks.

Where do I push it in, exactly? And how far? Just want to make sure I do it right.

As an aside, those are Style 5 wheels on your car, right? What size? I'd like the same for mine. How're they working out, and what rubber do you like?

[Jay 535i]

Here's today's update.

First, I popped the hood and removed the coolant cap. Since my car purged about a quart of coolant yesterday, the coolant was no longer right up to the cap's threads. I had to look deep down into the resevoir to see a little bit of coolant at the bottom.

I started the car. From cold, there was no action happening with the two resevoir hoses, which I think is normal for cold (?).

As the car reached normal temperature, the thermostat opened. When that happened, about a soda-can's worth of coolant came spewing out the top of the resevoir, just like yesterday. Up to this point I had still seen absolutely zero action through the two resevoir hoses, despite looking very closely. Even when revving at 3k, nothing was coming out or going in either of those little hoses.

I shut the car off, replaced the coolant cap, and restarted the car.

As per usual, the temp guage slowly started working it's way toward the red end. I shut it off at 3/4.

Then, as per the advice I've received in this thread, I started feeling around.

The rad top hose is HOT. The part of the rad very near the top hose (within about 5 inches) is WARM. Most of the rad and the lower rad hose is COLD.

I take it this is not normal. What are the odds of a blocked rad being the source of the problem?

I should have said this from the get-go: the thermostat was replaced about a month ago in the hopes of solving this problem. After that, the car ran fine for about 200mi before this problem resurfaced. Is that a clue?

BTW, Bruno has graciously agreed to help me. I'll talk with him soon, but I feel like I'm getting closer by process of elimination. Any more help would be appreciated.

Thanks.

[dacoyote]

[QUOTE=jaylebo]
I take it this is not normal. What are the odds of a blocked rad being the source of the problem?
[QUOTE]

It's either the rad(most likely) or a bad water pump in my option.

-Charles

[winfred]

trust me, pop the one off that comes from the radiator and clear the fitting on the tank, once it starts flowing it will stay cool IF theres not another issue, i've fixed several cars like this including a few that the bmw dealer diagnosed to have bad motor/head/head gasket, and several people on this board have fixed their cars by doing this


Up to this point I had still seen absolutely zero action through the two resevoir hoses, despite looking very closely. Even when revving at 3k, nothing was coming out or going in either of those little hoses.

[Jay 535i]

trust me, pop the one off that comes from the radiator and clear the fitting on the tank, once it starts flowing it will stay cool IF theres not another issue, i've fixed several cars like this including a few that the bmw dealer diagnosed to have bad motor/head/head gasket, and several people on this board have fixed their cars by doing this

I do trust you, but I don't understand you.

How do I 'pop it off' and 'clear' it? Should I undo both ends, or what?

Sorry for being a bit thick, but I'm new at this and don't want to screw up. Please be specific.

[winfred]

the hose that goes from the radiator to the bottle on the firewall where the cap is, remove it from the bottle and run a small drill bit through the nipple in the bottle (small bit means a bit that fits into the part of the fitting that the hose is clamped to, it gets smaller further in and you want to drill that out and kill the clog) with the hose dissconected from the bottle water should flow from the hose as it's almost always the nipple on the bottle that usually clogs, if no water will come from the hose then dissconect the hose from the radiator and blow through it, water should flow from the nipple in the radiator when the system is filled just by gravity


I do trust you, but I don't understand you.

How do I 'pop it off' and 'clear' it? Should I undo both ends, or what?

Sorry for being a bit thick, but I'm new at this and don't want to screw up. Please be specific.

[Jay 535i]

with the hose dissconected from the bottle water should flow from the hose as it's almost always the nipple on the bottle that usually clogs

Are you saying I should start the car with the hose removed, or that water will flow as soon as I disconnect it with the engine off?

Thanks.

[winfred]

with the cap on and hose off and the system full of water you could squeaze the hoses and get it to squirt, but the clog will almost certainly be in the nipple of the bottle that the hose ataches to as that's where the restriction is that whatever little piece of crud that's blocking flow is stuck, unbolt the bottle from the firewall, it's held with a couple 10mm plastic nuts then remove the hose that comes from the radiator, if it's never been off it will probably be held on with a crimp on clamp, it can be cut off with a pair of diagonal cutters at the crimped part that sticks out or sometimes you can open it up with a pick by jamming it into the crimped part and twisting back and forth, replace with a regular screw type hose clamp, at this point you can drill out the nipple


Are you saying I should start the car with the hose removed, or that water will flow as soon as I disconnect it with the engine off?

Thanks.

[MBXB]

Here ya go, dude,

http://www.bmwe34.net/e34main/trouble/Data/Overheating.jpg

See where the return hose runs into the tank? This is the same hose referred to earlier in the thread, in which you could use a weed whacker line to clear. Make sure that section where the return hose runs into flows freely. Better yet, make the hole bigger. You'll see the "hole" just inside the filler neck. It will look more like a pinhole. I used a hand 3/8 bit in a hand drill.

[Jay 535i]

with the cap on and hose off and the system full of water you could squeaze the hoses and get it to squirt, but the clog will almost certainly be in the nipple of the bottle that the hose ataches to as that's where the restriction is that whatever little piece of crud that's blocking flow is stuck, unbolt the bottle from the firewall, it's held with a couple 10mm plastic nuts then remove the hose that comes from the radiator, if it's never been off it will probably be held on with a crimp on clamp, it can be cut off with a pair of diagonal cutters at the crimped part that sticks out or sometimes you can open it up with a pick by jamming it into the crimped part and twisting back and forth, replace with a regular screw type hose clamp, at this point you can drill out the nipple

Thanks. Will do and report back.

[Jay 535i]

Here ya go, dude,

http://www.bmwe34.net/e34main/trouble/Data/Overheating.jpg

See where the return hose runs into the tank? This is the same hose referred to earlier in the thread, in which you could use a weed whacker line to clear. Make sure that section where the return hose runs into flows freely. Better yet, make the hole bigger. You'll see the "hole" just inside the filler neck. It will look more like a pinhole. I used a hand 3/8 bit in a hand drill.

Cheers. Is it really necessary to remove the hose and/or tank to do this?

[winfred]

theres no clearence to do it inplace and theres no way to access the hole without removing the hose, i've tried to clear them with a pick or wire though the cap and it just doesn't get it

[Jay 535i]

theres no clearence to do it inplace and theres no way to access the hole without removing the hose, i've tried to clear them with a pick or wire though the cap and it just doesn't get it

Alright. Thanks so much for your help and patience. I'll try this later and let you know how it goes.

Remember earlier I explained that when the thermostat opens, coolant comes spewing out the filler if the cap is off. If all that coolant isn't coming from the hose you'd have me drill out, where's it coming from? And how?

[Kalevera]

Alright. Thanks so much for your help and patience. I'll try this later and let you know how it goes.

Remember earlier I explained that when the thermostat opens, coolant comes spewing out the filler if the cap is off. If all that coolant isn't coming from the hose you'd have me drill out, where's it coming from? And how?
What's probably happening is the coolant is boiling in the water jacket and the pressure pushes it back up through the (larger) expansion tank hose, giving the volcano effect.

By the way, how do you know that the thermostat is opening?

best, whit

[Jay 535i]

What's probably happening is the coolant is boiling in the water jacket and the pressure pushes it back up through the (larger) expansion tank hose, giving the volcano effect.

By the way, how do you know that the thermostat is opening?

I assume the termostat is opening because the volacano, the heating of the rad top hose, and the needle reaching the half-way mark all happen at exactly the same time.

If the cause of the volcano, as you put it, is not somehow related to the opening of the thermostat, then this would seem like an awfully big coincidence. No?

On the other hand, if the volcano is somehow related to the opening of the thermostat, how would that work, exactly?

[Kalevera]

Jay

There are probably a couple of things going on with the car's cooling system.

Cooling systems work under pressure. The combination of antifreeze and water, when pressurized, have a higher boiling point than when not. Leaving the cap off of the expansion tank while a few gallons of coolant in the engine block and cylinder head start to cook means that the components of the mixture start to boil, especially if there's something wrong with flow, or the coolant's bad. As we know, boiling most liquids turns them into gasses. The gas has to go somewhere, so it starts to push coolant out of the expansion tank. This all makes sense if one of two things are happening: 1) the coolant isn't circulating, either through the radiator or through the block, or 2) the head gasket/cylinder head/block are somehow compromised (read: cracked).

Now, the thermostat in the M30 does one very crucial thing, and performs another task of lesser import. Primarily, it acts as the valve between the cylinder head and the radiator. When closed, no coolant from the radiator gets moved back into the block. The secondary task is one of manipulating a valve within the thermostat housing that directs coolant flow. While the thermostat's busy doing its thing, the water pump is happily uh....pumping...away: it picks up coolant from the water jacket and sends it right back to the thermostat housing. With a closed thermostat and (hopefully) a working expansion tank return line ('pisser"), some of that hot coolant gets pushed into the radiator via the upper radiator hose and back up to the expansion tank via the pisser. The rest gets circulated through the engine until the thermostat opens.

Because of the heat transfer through the liquid, the upper coolant hose will be as hot as the coolant in the engine is; it won't tell us anything about whether the thermostat is doing it's job. What will is the status of the lower radiator hose, which goes from being "cold" to "warm" as the thermostat opens, allowing the hot coolant to flow through the radiator, lose some of the heat, and flow back to the engine.

I've said it a few times before and I'll say it again: I don't think the thermostat's opening correctly, if at all.

Another thought: while probably not the only cause for its non-working state, having an inoperative tstat explains why the aux fan isn't powering on in overheating situations. The temp switch lives at the cold side of the radiator; without coolant flow, it doesn't know how hot the other side of the radiator is getting, and therefore won't turn on. It may be attributed to other issues (ballast resistor), but I'd suspect the coolant flow problem first.

Finally, here's a thread that detailed my experiences with this problem: http://www.bimmer.info/forum/showthread.php?t=9585

It's a lot of reading, but might help you out.

Good luck!

best, whit

[Jay 535i]

Jay

There are probably a couple of things going on with the car's cooling system...

Thanks a lot. That's really clear now.

I will try replacing the thermostat and see what happens.

What thermostat do I buy?

Do you have any tips/cautions about proper installation of the tstat that I won't get from the Bentley manual? I've taken note about what you've said regarding the O-ring.

BTW, when I said that the hot top rad hose indicated a working thermostat, I got that from the Bentley manual. Didn't make it up ;)

[dacoyote]

Bentley isn't perfect...

better then Hayes but not perfect....

-Charles

[Jay 535i]

Well, I did as you guys said, and the overheating has stopped.

I jimmied open the crimped clamp on the hose, removed the overflow tank, and pulled the two apart. To be thorough I undid the other end of the hose at the rad, too. I cleaned everything out.

If there was anything lodged in there, I didn't see it, but there you go. Problem solved.

A million thanks to everyone who helped out.

'Til next time...