Engine overheting

[alikom]

Hello All !

May be you can help me? I own a 525 iX touring (e34 with m50b25 engine, I hope) It is european model. Yesterday suddenly it started overheating, the temp needle goes to red area, the temperature warning goes on. To day I did little study. I did run the car for 10 min or so, it warmed up and temp needle was at 1/2, than I got the road and the teh needle went up to red area. I had AC on. Then I switched off the AC and turned on full interiro heating. The temp needle came in between 1/2 and 3/4 marks. As soon as I turned of the heating it went up to the red area back. I stopped the car and on running engine opened the hood. It seems to me that the fan was not running to fast, even the temp needle was at the begining of red area. I COULD STOP THE FAN BY HAND AND EVEN SPIN IT BACKWARDS WHILE ENGINE WAS RUNNING. Also, when first time (after cooling down overnight and before I did all of above) turned on the engine, while idling auxilary fan went couple of time on , but after I never heared the aux fan voice. The big hoses connected upper left and bottom right corner of radiator both are hot.
Upper one got hot quicker that lower one. Is that simptoms the termostat and fan clutch problems or something else? Thank in advance.

[632 Regal]

first thing I would do is replace that fan clutch! overheating is NOT your friend on these engines.

[genphreak]

first thing I would do is replace that fan clutch! overheating is NOT your friend on these engines.Indeed, one or two overheats can ruin an L6's lifetime... either now or in a bit later on.

Don't let it go above 3/4 at all, or don't drive it. Fix ASAP.

The needle should stay perfectly in the middle when fixed; so once the fan clutch is renewed, check the operation of the thermo fan too, just in case.

One faulty fan can sometimes be managed by the other fan until extreme conditions (ie bad traffic) are encountered, then all hell can break loose- next thing you know the head is cooked and it's only fixed by an expensive repair and about 2 weeks in the shop.

Good luck- a clutch fan is at least a simple and cheap fix (and a wear item). Nick

[Ross]

Refrain from putting your hand into a moving fan blade after replacing the clutch!

[alikom]

Well, in fact I was not doing that by hand but with peece ow wood. Anyvay the result is the same. I can stop the fan and even spin it backward when engine runs.

[Alexlind123]

You need a new fan clutch, its not too hard to figure out.

[alikom]

You need a new fan clutch, its not too hard to figure out.
Is that only? No thermosta exchange? Soembody told me if I got overheat once, thermostat has to be changed. Is that true?

[alikom]

:(
You need a new fan clutch, its not too hard to figure out.
And how difficult is to change that fan clutch?:(

[632 Regal]

about a 2 on a 1-10 scaqle of difficulty. do a search it has been covered here extensivly.

[Chris'91'525i]

:(
And how difficult is to change that fan clutch?:(

It can be very difficult if you turn the big 32mm nut that holds the fan on the wrong way.
It has left hand threads.
So turn the big nut the opposite way that most nuts thread off and on.
Other than that, it's pretty straight forward job........

[Mendozart]

If you can get ahold of a fan clutch tool it might make things easier. I hadn't had to use one on my first 4 or 5 repairs but just recently ran into a stubborn one. The tool holds the pulley still while you turn the 32mm wrench clockwise(facing the engine from the front of the car).

[632 Regal]

http://www.bimmer.info/~regal632/Fan%20removal%20tool.jpg

[pzero]

Apologies for resurrecting a few month old thread, but had a search around the forum and this sums up my fault exactly, so seemed a waste to clutter teh place up with a duplicate.

Exactly the same problem as the original poster, on my UK E34 520i 24v - M50 engine. The fan could be turned by hand with a little resistance when cold, but when hot (and I mean really hot - temp into the red a few times recently whilst idling in traffic jams), even less resistance, to the point that as with the original poster I can stop and spin backwards the fan by hand with engine running, and when engine stopped but hot, a tap of a fan blade sends it spinning freely.

I've replaced the thermo coupling this morning, but something odd is going on. A brand new coupling fitted, and when started from cold was moving loads more air than the old coupling. Great I thought. But temp hit normal... then climbed... then climbed... almost into the red, I checked the fan again, and found was moving no air at all. stopped the engine, and just like teh old one, despite being hot it span freely. Less resistance than when cold, which doesn't sound right to me.

This was a new coupling, which I can only presume was faulty on arrival, unless I'm misunderstanding how this thing is meant to work?

[DaveVoorhis]

Possibly a defective fan coupling, but it could also be a defective thermostat which is restricting the flow of hot coolant into the radiator. The fan coupling action depends mainly on air being heated by the radiator. If the radiator doesn't get hot enough, the fan coupling doesn't couple. Meanwhile, your engine turns incandescent and melts...

[Omega]

http://www.bimmer.info/~regal632/Fan%20removal%20tool.jpg

Christ Jeff. How big are the rats in your barn if they can bite through steel bars like that?.... :D

[pzero]

When up to temp, the top radiator hose and rad itself heating up fine, no cold spots, so assuming that the thermostat is functioning ok?

[alikom]

When up to temp, the top radiator hose and rad itself heating up fine, no cold spots, so assuming that the thermostat is functioning ok?

Hi all !

In my case , I exchanged fan clutch, thermostat and waterpump (it was not necessary, but 14 years with original pump, well ....)

http://www.pelicanparts.com/bmw/techarticles/tech_main.htm

Look at address above, go down to cooling system and you will find how to replace thermostat and waterpump . Perfect description with pictures:D

[pzero]

Hi all !

In my case , I exchanged fan clutch, thermostat and waterpump (it was not necessary, but 14 years with original pump, well ....)

http://www.pelicanparts.com/bmw/techarticles/tech_main.htm

Look at address above, go down to cooling system and you will find how to replace thermostat and waterpump . Perfect description with pictures:D
Many thanks Alikom, best guide I've seen yet and loads of other useful stuff. Spoke with the suppliers of the thermal coupling I fitted this morning, they are sending a replacement. Might ask them about a price on a thermostats, because although mine seems ok (top hose hot, bottom hose cool), car is 15 years old, five of which I've had it, and if it's not an expensive thing, might as well do it. M50 engine, which as I gather had the water pump with plastic impellors which could do with replacing, will check that out also. Thanks, I'll post again when I know how succesful I've been...

[alikom]

Many thanks Alikom, best guide I've seen yet and loads of other useful stuff. Spoke with the suppliers of the thermal coupling I fitted this morning, they are sending a replacement. Might ask them about a price on a thermostats, because although mine seems ok (top hose hot, bottom hose cool), car is 15 years old, five of which I've had it, and if it's not an expensive thing, might as well do it. M50 engine, which as I gather had the water pump with plastic impellors which could do with replacing, will check that out also. Thanks, I'll post again when I know how succesful I've been...

That's true, M50 has water pump with plastic impellers and it could happen that , those impellers are braken. When I replaced water pump, mine were good, but before replacement when dig different forums, many posts were about pump impellers as well.

[pzero]

Back again I'm afraid.

Well new thermal coupling arrived, fitted... same result. No resistance despite temp needle hitting the red. As with Alikom, (not that I advocate sticking things in the path of rotating fans!) I am able to stop, hold still, and even spin backwards the fan when the engine is running, and the chances of getting two defective fans in a row must be pretty slim.

Checked the hoses, top heating up nicely, bottom fan feels cool enough. Checked the rad again, which was very hot when checked before, however this time checked it a bit more carefully and felt it in a few places. Radiator is only hot down one side, alongside the expansion tank - cool in the middle right in front of the fan. Maybe I'm barking up the wrong tree here, but a thought that occurs to me is that a blockage in the rad is causing the water to flow around the outside, NOT close enough to the fan to heat it up and cause the thermo viscous fluid to stiffen? Does that sound feasible? (forgive my ignorance!)

[alikom]

Back again I'm afraid.

Well new thermal coupling arrived, fitted... same result. No resistance despite temp needle hitting the red. As with Alikom, (not that I advocate sticking things in the path of rotating fans!) I am able to stop, hold still, and even spin backwards the fan when the engine is running, and the chances of getting two defective fans in a row must be pretty slim.

Checked the hoses, top heating up nicely, bottom fan feels cool enough. Checked the rad again, which was very hot when checked before, however this time checked it a bit more carefully and felt it in a few places. Radiator is only hot down one side, alongside the expansion tank - cool in the middle right in front of the fan. Maybe I'm barking up the wrong tree here, but a thought that occurs to me is that a blockage in the rad is causing the water to flow around the outside, NOT close enough to the fan to heat it up and cause the thermo viscous fluid to stiffen? Does that sound feasible? (forgive my ignorance!)


As far as I understand, the fan clutch (thermocupler) should spin freely when engine is cold and blow lot of air when engine is hot. The cooling system is pretty simple in these cars and has four main components -- radiator, fan and fan clutch, water pump and thermostat. Most expencive parts from this four are fan clutch and rad.

In my case I exchanged three of 'em. fan clutch, thermostat and water pump. In your case, I think the rad can cause this, since you have there some cold areas. In fact to replace rad is not difficult at all. The link I gave you, decribes it. Since you get fan clutch, get thermostat and pump as well. If you had had the engine overhited , you need to exchange thermostat anuway. This device is very heat sensitive thing. Also, it is good idea to exchange the pump. But first start from thermostat and then with rad. Also try to give good massage to big rubber hoses coming from rad. May be they are clogged.