m40 engine overheating

[jamiedo]

Hi all,
Have had a look through some of the threads to do with this problem but cant find the answer...

I have a 1993 518 / e34 / M40 engine 67k miles...

Its been off the road for a while as I've been doing alot of work to get it MOT ready (I told myself 3 weeks ot begin with, its been 13 months...)

It passed its MOT, but it is overheating. Have tried bleeding the air from the system, but today realised that the water is not getting hot (or even warm) in the radiator, or in the hose going from the bottom of the rad into the water pump (front of the engine block).

The water is heating the radiator matrix, so I assume the pump is working properly...

The Temp sensor seems to be working properly, and the thermostat was replaced when I changed the cylinder head...

HELP! Any ideas would really be appreciated.

[bubba966]

Sounds like you might have a partially or maybe mostly blocked/clogged radiator.

You might want to try flushing out the radiator from both in & out hoses on the radiator to try and blow out any crud that's in there. As it's most likely to be clogged in the inlet side of things run pressurized water from the radiator outlet so that it's pushing water backwards through the radiator to blow the crud out of the inlet. Then try it on the inlet to blow out the outlet. Do that a few times and you should get out as much as is going to be possible.

If that doesn't work you'll probably need a new radiator.

[whiskychaser]

Hi all,
Have had a look through some of the threads to do with this problem but cant find the answer...

I have a 1993 518 / e34 / M40 engine 67k miles...

Its been off the road for a while as I've been doing alot of work to get it MOT ready (I told myself 3 weeks ot begin with, its been 13 months...)

It passed its MOT, but it is overheating. Have tried bleeding the air from the system, but today realised that the water is not getting hot (or even warm) in the radiator, or in the hose going from the bottom of the rad into the water pump (front of the engine block).

The water is heating the radiator matrix, so I assume the pump is working properly...

The Temp sensor seems to be working properly, and the thermostat was replaced when I changed the cylinder head...

HELP! Any ideas would really be appreciated.
The bottom hose may take a while to get hot. The million dollar questions are:
1. Is the heater getting hot
2. Is the top hose getting hot

[e34.535i.sport]

Flush the rad then check get it all back together, Start it up and see if the upper adiater gets hot... If not you may have a faulty thermostat even if its been replaced.

When you bled the air did you have the heaters on full and do it facing uphill etc?

[jamiedo]

Hi all,
thanks for the responses so far.
The top hose and heater are getting hot... the bottom hose and rad are stone cold...

When I bled the system I had the heaters on full, but no hills to use... I'll try flushing the rad and sticking the front on axle stands when I bleed it through.

I'll let you know how I get on - thanks again for the ideas...
J

[jamiedo]

So... I checked the rad - no sign of blockage. Changed the thermostat, started as normal - bleeding air with engine running etc.

The rad and bottom hose are now getting hot. But... as the temp guage started to go just over the middle (12 o clock) I bled the air again, and it was nothing but steam... Is this just something that happens when the engine reaches a certain pressure, or is this a problem?

From the sound of it the water pump bearing is making some crunchy noises, so I'll be changing that in the next few weeks - could this lead to the problem?

[DaveVoorhis]

as the temp guage started to go just over the middle (12 o clock) I bled the air again, and it was nothing but steam... Is this just something that happens when the engine reaches a certain pressure, or is this a problem?

From the sound of it the water pump bearing is making some crunchy noises, so I'll be changing that in the next few weeks - could this lead to the problem?
Steam after properly bleeding the system is not normal. Steam after improperly bleeding the system is common. Crunchy noises from the water pump are bad. Fix now or suffer soon.

[Ross]

It's not circulating. Water pump time now, or head gasket time later.

[jamiedo]

I thought because the rad matrix was getting hot it must have been circulating? hmmm either way, already done the head gasket and dont fancy all that mess again - I'll chuck a new water pump on, do the cambelt whilst I'm there and see what happens - thanks for the advice.

(The engine sounds tappety as well - but I figured that wasn't related...)

[Mordan]

Hi all,
Have had a look through some of the threads to do with this problem but cant find the answer...

I have a 1993 518 / e34 / M40 engine 67k miles...

Its been off the road for a while as I've been doing alot of work to get it MOT ready (I told myself 3 weeks ot begin with, its been 13 months...)

It passed its MOT, but it is overheating. Have tried bleeding the air from the system, but today realised that the water is not getting hot (or even warm) in the radiator, or in the hose going from the bottom of the rad into the water pump (front of the engine block).

The water is heating the radiator matrix, so I assume the pump is working properly...

The Temp sensor seems to be working properly, and the thermostat was replaced when I changed the cylinder head...

HELP! Any ideas would really be appreciated.

I feel for you. A similar thing happened to my m40. Now that i have some time's off, I will work on it.
Mine is overheating because, the head gasket is screwed (by the previous owner), as he drove with a failing water pump.
You changed the cylinder head you say. Did you pressure/temp test it to make sure it was alright? I will have to do that with mine.
I will have to change the water pump as well. The water pump is critical element in any overheating issue.
does your heater works? because mine does not.

[jamiedo]

Hi all,

Well, water pump changed (the old one was a right pain to get out - bits snapping off all over the place - thank god for rubber mallets!).
It's a little better, but is still getting to a certain temp then lots of steam from the bleed screw... does anyone know if this points to a certain problem?

Or is it likely I'm just not bleeding the system properly and it's getting airlocked somewhere??

The water is circulating fine and doesn't seem to be loosing any water, the heaters are getting hot and the rad / bottom hose / top hose all seem to be getting nice and hot... Any ideas would really be appreciated!

[Ferret]

Hi all,

Well, water pump changed (the old one was a right pain to get out - bits snapping off all over the place - thank god for rubber mallets!).
It's a little better, but is still getting to a certain temp then lots of steam from the bleed screw... does anyone know if this points to a certain problem?

Or is it likely I'm just not bleeding the system properly and it's getting airlocked somewhere??

The water is circulating fine and doesn't seem to be loosing any water, the heaters are getting hot and the rad / bottom hose / top hose all seem to be getting nice and hot... Any ideas would really be appreciated!

Are you using the correct amount of coolant? These engines are very sensitive to coolant and boiling points etc. If you run them without coolant I seem to remember they boil over *very* easily, and opening the bleed screw while the engine's at temp will cause most of the contents to flash boil.

If your heater and radiator are getting hot, you've definitely got good flow, I'd just be careful about opening the system when it's up to temp! You're only supposed to bleed the system up when the engine's luke warm, doing otherwise just lets air back in the system.

I'd bleed it up cold with lots of coolant, then run it up to temp and see if the needle stays stable.

EDIT: Try bleeding her up with the radiator top hose off, pour water down the top hose towards the thermostat as well... did you insert the thermostat with the arrow pointing upwards?

[jamiedo]

Thanks Ferret - I wasn't using any coolant (wanted to test the system first so was just using straight water - I'll get some coolant and give it a go. I didn't know that you can only bleed the system when not at running temp...

Hopefully I'll be able to work it out now - I did get the thermostat in the right way I think... There was no arrow but I mimicked the alignment of the old one and the top hose is getting hot etc.

I'll have a play on Sunday and will let you know how it goes.
J

[SnakeyesTx]

How are you bleeding your radiator/engine? If you're not using the bleeder screw in the top of the radiator (if yours is equipped with one) then you're running it severely short of coolant in the first place. If you try running the engine with that bleeder screw out, you're going to have quite a serious fountain of coolant shooting through it (if coolant shoots out of the bleeder hole, chances are your pump is working great since usually the pump failure is the plastic impeller breaking apart).

The bleeder screw is right next to the radiator cap (looks like a large +). Basically you just un-screw that, open the rad-cap and fill until the bubbles stop gurgling out of the bleeder hole (or until coolant starts to shoot out of it). I lost an M50 because I didn't know about that screw and drove to work almost 2 gallons of coolant short... warped head, blown head-gasket, etc etc. :D


EDIT : See?

http://www.realoem.com/bmw/showparts.do?model=HA12&mospid=47367&btnr=17_0089&hg=17&fg=05

#7 "vent screw"

[jamiedo]

Am bleeding using the screw - despite using coolant the engine is still overheating...

It's taking about 10 minutes (the temp sat at 12 o'clock for quite a while) and the top hose felt very tight (like a build up of pressure or something...). The water is stilll circulating but the darn thing is still getting too hot...

Anyone have any more ideas?

[Ferret]

Am bleeding using the screw - despite using coolant the engine is still overheating...

It's taking about 10 minutes (the temp sat at 12 o'clock for quite a while) and the top hose felt very tight (like a build up of pressure or something...). The water is stilll circulating but the darn thing is still getting too hot...

Anyone have any more ideas?

The top hose should feel very tight under normal operating temps... have you changed your fan coupling, it could be that the fan isnt pulling enough air through the radiator!

Edit: You can check if it's the visco fan causing all the trouble - if you take it for a drive at a constant speed around the block, the coolant temp will stay the same. As you pull up to a stop it should then boil over.

Alternately get a desk fan or the like and sit it on your front bumper on 'high' blowing air through the rad. If it has aircon switch it on and the aux fan on the front of the rad should start spinning.

[BobHarris]

Viscous fan is a definate possibility. My M40 had a spell of over heating and it turned out to be the fan. I couldn't afford a new one at first so I drill through the clutch on ot in two places and bolted it together. This worked a treat but we soon got fed up with the noise. (The car sounded like a bus all the time).

[jamiedo]

Cool - I think I'll try the drilling method and see if that improves anything... I dont mind sounding like a bus for a bit... I think I can get a replacement part for abuot £40, so if that works I'll get a new one...

I haven't had the fan shroud on for some time - this wouldn't cause any problems would it?

[Ferret]

Cool - I think I'll try the drilling method and see if that improves anything... I dont mind sounding like a bus for a bit... I think I can get a replacement part for abuot £40, so if that works I'll get a new one...

I haven't had the fan shroud on for some time - this wouldn't cause any problems would it?

It'll only make a difference when your fan starts to fail

I've been running my 540 around for 12 months completely without a cowling and it's running fine...

[jamiedo]

Well, I've taken the coupling off - the car doesn't have aircon and isn't insured on the road at the moment so am not sure how to test - one thing I do notice is that when holding the nut and spinning the fan, it has a fair bit of resistance, then after about 10 secs of spinning there is much less resistance... Does this mean it's shot and time for a new one...?

[whiskychaser]

Well, I've taken the coupling off - the car doesn't have aircon and isn't insured on the road at the moment so am not sure how to test - one thing I do notice is that when holding the nut and spinning the fan, it has a fair bit of resistance, then after about 10 secs of spinning there is much less resistance... Does this mean it's shot and time for a new one...?

If you want to test the fan clutch, check this out:

http://www.mwrench.com/Whitepapers/FanClutchtest.pdf

[632 Regal]

The way I would suggest to see if it's bad is if it sounds like a school bus when its hot and taking off from a light. Same sound with a cold start for a few minutes means the clutch is good. No bus sound = bad clutch fan.


Well, I've taken the coupling off - the car doesn't have aircon and isn't insured on the road at the moment so am not sure how to test - one thing I do notice is that when holding the nut and spinning the fan, it has a fair bit of resistance, then after about 10 secs of spinning there is much less resistance... Does this mean it's shot and time for a new one...?

[jamiedo]

Thanks for the responses...

I dont have any bus sound when cold, or when very hot... At least I feel like I'm getting nearer solving the problem... I've nearly replaced all the cooling components trying to sort it out!
What's the best way to botch the viscous coupling? is it a case of drilling through the inner and outer parts and clamping them together with a length of metal?

[Ferret]

Thanks for the responses...

I dont have any bus sound when cold, or when very hot... At least I feel like I'm getting nearer solving the problem... I've nearly replaced all the cooling components trying to sort it out!
What's the best way to botch the viscous coupling? is it a case of drilling through the inner and outer parts and clamping them together with a length of metal?

You can botch it like this... though it's not an ideal situation. You can drill straight through it about 1 inch out from the centre - but remember to balance by having at least two drilling and bolt points... if you dont your water pump bearings will be toast in no time.

Also, I'd not advise taking it over 3-4k rpm if the fan plastic itself is old - these fans will spin at *very* high speed if the clutch disk is locked totally.

DO NOT under any circumstances touch the throttle if you're running the car with the bonnet lifted when you've locked up the fan clutch, if it lets go at high rpm you'll have fairly heavy sharp bits of plastic flying around at 100mph+

[jamiedo]

Well, I managed to get a £20 new part so I have replaced the fan coupling (on closer inspection the old one had a goo leak from the front).

It is running better now - temp after 15 mins of running stationary is sitting just right of the 12 o clock mark... creeps up and down a little but doesn't go too far from 12... I hope this is the right place for it to be!?

thanks for all the advice - you guys beat the haynes manual troubleshooting bit hands down...

Now all I have to do is work out the weird pinking noise...