I have been experiencing a new phenomenon with my 2002 330xi (62,000 miles) for the last couple of weeks. Once the engine gets warmed up and during the first five or ten minutes of driving the temperature gauge shoots up to the red and then goes back to normal. Sometimes it goes to the red and then back to cooler than normal, then back to normal. Over the past weekend, I let the engine warm up while I cleared snow and ice from the car. After about ten minutes the temperature gauge was up in the red. It was less than 20 degrees that day. One more thing that I am not sure is relevant. The heater works very poorly and takes several minutes of driving to get any heat going and then it often begins to blow cool. Any thoughts? Thank you in advance. Sam
Our family literally just suffered through something similar, only the temperatures never went back down to normal unless we stopped the engine. This is currently the problem in the family's Nissan Sentra. What was happening was that no hot air was being blown from the vents even if set all the way to hottest setting. About 20 minutes later, the car overheated. If you are to wait for it to cool off, you could go a block but it would overheat again. Now the car is stuck about 70 miles away from home and the person driving the car had to come back via train. I think the thermostat is shot, and our mechanic (that we called) told us the same thing. I think your thermostat might be going as well...
You probably need a thermostat but definitely check the coolant level. Does the car have heat (hot air from the defrost vents) when it is overheating? If not there may be other problems.
If the hot air cuts out unexpectedly, there is often an issue with air in the system or the pump not pumping (bad impeller,) which can easily cause intermittent overheating. Make sure the coolant is full and the system is bled properly. Do not ignore the gauge, and make certain that the coolant stays full until the issue is resolved. DO NOT overheat your car again! This is possible if it is 20 below! I have seen and heard of too many people that have lost engines because of the cooling system on E46 and E39. Also remember that if it is overheating that a tow is always cheaper than a new motor. I cannot stress this enough as the M52TU/M54 does not usually survive overheating the way the cast iron blocks do.
Thank you. Just dropped the car off for water pump and thermostat replacement. New belts too. The car only overheated for a few second before it went back to normal. Do you think there is any permanent damage??
There shouldn't be any damage as long as you shut if off in time. Define a few seconds... a few seconds could ruin your engine or a few seconds could just be your savior. Was it like 5 seconds or 15 seconds?
Moosehead already mentioned it but rapid fluctuations from red to normal AND intermittent heat are classic symptoms of air in the cooling system. Step one should be to fill and bleed the system then check for leaks and go from there.
Permanent damage usually occurs when someone "shut it off as soon as they noticed it was overheating." This usually means the car shut off from overheating and there was no coolant in it at all. You have not done any permanent damage I am 99.9999999% sure. I only wanted to warn you away from running your car with a know cooling system issue without actually regularly checking your coolant and being able to see the gauge at all times. Even so, when you run the car out of coolant, teh gauge will not work, which is why you should check the levels regularly.
