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7 Series (E23, E32, E38, E65, E66)General discussion and technical help for all year 7 series cars.
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Your Ride: 88 735i
I have a 1988 735i that has a problem my local mechanic is having difficulties figuring out. (I don't have a BMW shop in my local area). The car seems to run fine. It is not overheating. In fact it almost stays too cool. The biggest problem, however, is this:
After the car has been running, and heats up to normal temp, the pressure seems to build in the coolant system. There is a pressure release hose that comes off of the fill tank and drains down onto the ground (not into a reservoir tank) as the car begins to cool when parked. In fact, if you remove the fill tanks cap, the fluid leaks out the hose rapidly. The car does not appear to leak while driving, only after it is parked. Now I have noticed that the car does not stay up to temp while driving causing the heater to only pump out cool air instead of heat. The last time that particular problem happened we flushed the radiator to clear out any air bubbles and it worked fine again for a few months. He still is unable to figure out what is causing the pressure buildup.