Re: overheating 535i (archive)

I recently had the 535i overheating problem as well, there are many past posts on the board about it. Unfortunately, it could be any component in the cooling system short of a head gasket job (big $$$).
1. Flush coolant and add new coolant. Notice the cooler and content of old coolant. If it is rusty color or has particles in it you might have a plug somewhere. It could be plugged at the little hose to the radiator, big hose to the thermostat, or somewhere after the water pump, mine was all gunky. Buy a good flush. Do a coolant compression check.
2. If you pass that test, replace the fan clutch. If you can grab the fan clutch with out cutting your fingers off, then it is bad. I suggest using a wadded up magazine or newspaper instead of your hand to check it.
3. If your car sits at above the mid temp part of the gauge on long trips (start and stop driving), then maybe your thermostat is bad. My car would only overheat after 30 minutes of driving. If you had a mechanic replace your thermostat and you didn't see the old one get thrown away, he could have been lazy and drilled a hole through it, this is a big no go, it happened to me. Buy a thermostat and install it yourself, it could save you big money later.
4. If you still haven't found a problem, go to your radiator, have it checked for clogs.
5. Next is the water pump.
6. Last is head gasket check. Check your oil. Drain all oil out of the oil pan and check it to see if there are two layers. One layer would be oil (bottom) and top layer would be water/coolant (top), this means you have a leaking head gasket (big $$$)

I hope this helps, I have done everything in this process, use only a mechanic that you can trust.

Derek
'00 528i
'89 535i

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