A friend just bought a 94 525T. The engine slowly overheats after about 10 miles of travel. It looks like a new radiator and water pump were installed. Any ideas. Scott
Check the water pump. If it's one of the original ones, it has a polymer impeller that will degrade and come apart. It's possible that one or more of the blades/fins is no longer attached.
Does it have the typical "boil over" when it overheats? I bought my 530 at a very low price because it was 'overheating' according to the dash gauge. I confirmed the tempratures coming out of the pump and in & out of the radiator and eveything ooked good so I replaced the appropriate sender (there are 2 in our cars, one for the DME and another one for the dash gauge) and eveything has been fine since then.
If radiator and pump were recently changed, the first thing to check is if the system was bled properly to get all air out. I have found that if not bled properly, you can get boiling in the head passages near the sensors which will indicate overheating even if the block is not affected. This is still not a good situation. Prolonged boiling due to trapped air pockets, will cause fluid loss and complete overheating eventually. Next thing is to have the system pressure tested. If there is a small pressure leak, the fluid can start to boil with hot engine under load even though it seems fine at idle.
on my 95 530i i just had to replace the water pump, radiator hose, and thermostat . before i got it fixed the the temperature gauge woud go to red in less than 10min of driving
