My wife was driving the car in heavy traffic today and the message of 'coolant temperature - see handbook' came up on the display after about 5 to 10 mins. She continued to drive the car in the traffic, switching the engine off periodically, and the coolent temp needle apparantly crept up well into the red area! Despite this, once out of the traffic the car apparantly drove fine, and the temp came down to normal (just below mid-point).
Does any body have any idea why it would do this? I have checked the coolant level - it is spot-on (should be - it has just passed its Insp II service). Is there a fan that should come on after a certain temp is reached? If so, how do I make sure it works?
Apparantly the a/c became pretty poor when the engine was hot - though I guess this is not surprising.
Paul said: ...My wife was driving the car in heavy traffic today and the message of 'coolant temperature - see handbook' came up on the display...
Oh oh..
I bet the handbook says "Stop engine emmidiately, and seek road assistance".
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...She continued to drive the car in the traffic... ... and the coolent temp needle apparantly crept up well into the red area!...
Wow.. she knows more about what conditions the S38 engine can withstand, than BMWs finest engineers. (read: tell your wife that when the car says "problems, read handbook", then if she does not understand the effects of ignoring the warning, then she should actually read the handbook, to be enlightened. Also tell her that red color in the carworld means "Stop!", be it a red trafficlight, redline on the rev-meter, or redline on the coolant temp-gauge).
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...Does any body have any idea why it would do this? I have checked the coolant level - it is spot-on (should be - it has just passed its Insp II service). Is there a fan that should come on after a certain temp is reached? If so, how do I make sure it works?
When you checked the coolant level, you might have noticed a large fan at the front end of the engine, this is the cooling fan.
It is beltdriven, and have a viscose clutch, that engages it when coolant gauge is about halfway. Notice that the fan runs even when not engaged, but not at a high speed.
HowTo check its function: hmm.. open the hood, and start the engine, if cold you should notice that the fan does not blow a large amount of air. (and if you dare, you can stop the fan with a finger). When the engine gets hot, the fan should engage, wich you can tell by it moving alot more air, not beeing possible to stop by finger touch, and if you rev the engine (only a little, for 1sec at a time), you can hear that the fan blows lots of air around. This is normally not something that fails, but i dont have a better idea why your engine overheated.
Hope you figure it out, or someone have better advice to give you.
Dont drive the car untill the problem is solved! a new engine is extremely expensive for this car. (listed at £10654,- in the ETK for a 3,6L & £11654,- for a 3,8L).
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Mvh. Finn Donati
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Last edited by Donati; 20th September 2002 at 03:11.
Thanks for the reply - however, being a degree qualified mechanical engineer, I am vaguely aware of the principles of a combustion engine - and therefore I know where the cooling fan is. I was really after a pointer of where I should cencentrate my efforts to solve the problem.
My plan tomorrow is to check the thermostat is guiding water to the rediator, and THEN to check that the viscous fan is engaging at mid+ temperatures. I just wondered whether anyone has had any experience that could suggest a better approach.
By the way you asked if there was a fan that should engage, it sounded like you did'nt know if there was a fan at all. I thought this was a bit strange, but hey.. some people have zero interest in how the car works.
Sorry, i can think of no pointers to give you, but i will follow this thread to see what can make the engine overheat, besides a broken belt. (i had all 3 belts replaced on my engine today, since i had no idea how old they where, and to hopefully avoid getting a broken belt at some point. (and it was not a moment too soon, one of the belts even had some parts of it missing)).
And btw. i noticed your post-count and date registrered, and so want to welcome you to this board. Im sure you will find many pieces of great info and advice on whatever problem you might have with your M5, afterall this board probably have the largest collective knowledge on these cars, outside Munich.
Incase you dont know of it, DeWitt have constructed a great E34 M5 FAQ, definately worth a visit.
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Mvh. Finn Donati
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Last edited by Donati; 20th September 2002 at 03:56.
(should be - it has just passed its Insp II service).
Take it back to the dealer and complain. If you do not want to go that route or are affraid of even driving the car you can do several things that might have been missed due to neglegence when the car was serviced although I doubt a reputable place could have missed such things.
Check the percentage of coolant in the resivoir tank. Most brands of coolant specify around a 50/50 coolant to water ratio depending on driving conditions. Since your car overheated I would want to check if the percentage of coolant is too low.
Try bleeding the system. Air pockets would cause hot spots in your engine but I am not sure if it would cause the temp gauge to dip into the red like you described.
Also check and make sure there is no coolant in oil or no oil in coolant. Either of these could mean a leaking head gasket. That would be bad.
I have an experience of overheated engine with a normal coolant level and a working fan.
I bought my car in the spring and it was quite a cold one. Therefore the oil cooler managed to keep the engine temperature at normal level so I did not notice that there actually was a problem. When I later took the car on a trip through Europe, it kept telling me that it was too warm. I had a BMW garage check it and they said it was fine?! In Germany I decided to test the speed limit function (250 KM/h) and it worked fine. However the engine overheated!!! I noticed a VERY expensive sound from the engine and stopped. The car was taken to a BMW garage that offered to fix it for €12.000 and this was 6 years ago!!!!
I decided to fix it myself and I did actually find the problem. The engine radiator was filled with sand where the air should pass through. There was nothing blocking the flow of the coolant on the inside. I had about 10% of airflow through the radiator. My guess is that some previous owner had been very keen on making sure that he washed the "radiator" when washing the car. He probably cleaned the A/C converter from sand and moved the sand to the enginge radiator. The A/C converter sits in front of the radiator and it was completely clean, no sand. There is no way to detect if you have sand in the radiator by just looking at it.
I suggest that you fluch the radiator from the engine side (you do not need to remove it from the car) and see if you get any sand out from it. YOU DO NOT WANT TO SEE THE INTERIOR OF AN OVERHEATED ENGINE!!. Not only does it look bad, it creates a very painfull feeling in your wallet
You should aproach your overheating problem with a bit of common sense and check the following, after all althought the engine is fairly complex the cooling system of the car is relatively simple
1) Check coolant level with engine cold, the cooling system relies on water to cool the engine, Should you need to ttop up the cooling system the engine uses a mixture of BMW antifreeze and distilled water in a ratio of 50% each.
2) check the cooling fan, make sure its not obstructed for any uknown reason, ocasionaly it may happen that something could get sucked up if there is no engine under tray that could jam the fan, like some plastic sheeting, etc
3) if there is nothing obstructing the fan or the radiators, check the fan movement, when the engine is cold the fan free wheels up to certain extent, you can even get the fan to stop if you are brave enough, although I would not recomend sticking your fingers, use a paint brush or some thing similar that will slow down the fan but not damage it, you will notice that if you do this with engine running from cold start up that there should be some drag but nothing excesive.
4) feel the radiator, for it to cool the engine water should circulate through it, with the engine cold the thermostat prevents the water circulating the through the rad, so let the engine warm up by letting it idle and feel at regular intervals the the top and bottom radiator hoses, at the same time put the heater on inside the car with the engine warm you should get hot air
5) if you dont get warm air out of the heater it could be mean that there is a air lock in the system or that the water pump has failed, which would also explain the overheating, if you do get hot air out of the heater, but the bottom hose of the rad remains cold it would point towards the thermostat having failed in the closed position
I hope the above pointers help you trace your overheating problem.
In my haste to post a response I forgot to mention another posibility
6) If the water appears to circulate normally throught rad and cooling system but you find that after a while the temperature gauge starts to creep up slowly, it could be that the viscous fan coupling has failed, try revving the engine the cooling fan should make more noise and move a lot more air in comparison to when the engine was cold, and if you try to stop the fan via the same method as before it should be a lot harder if not imposible, if this isnt the case, I believe that viscous fan couplig has failed, this coupling has an internal thermostat that engages the fan once it reaches a certain temperature.
Hi!
If I understood right, your car overheats only in city traffic, not in high speeds.
That suggests a viscous clutch failure on the fan which by the way is NOT unusual. That fan is meant to assist on the cooling of the engine in low speeds when the speed doesn´t suply enough air for cooling. When that fails it´s quite typical that the car overheats in low speeds. If the fault would be on the head gasket or waterpump, the engine would most propably overheat when pushing the engine. Of course nothing´s certain but the way I see it I would check the fan first(easy, relatively cheap)
I had that fault on my previous car.
Just my 2 cents
Drsakke
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