Question about 1997 BMW 7 Series

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Coolant leak and overheating

I need help...I have a 98' bmw 740il about 6 months ago i got a leak in the expansion tank, replaced it then thermostat went out, replaced it thought my troubles were over then the water pump went...replaced it...every thing was good for about 1 month and the check coolant light started coming on everyday...noticed a leak in the rear of the engine somewhere when the car gets hot it almost pours out and theres steam and light spray back there...haven;t found the leak yet....thought it was the gaskets of the water pipe in the rear but changed those and still happens...any ideas????....i miss driving my car.

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I had a water leak on my 730i I found it after much trouble.A hairline crack in the plastic thermostat housing which onlly opened up when hot and of course got worse as water level dropped.Hope this helps.

Posted on Oct 30, 2009

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Mine did the same thing.....Heater control valve was cracked.

Posted on May 09, 2009

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Its hardly one of the frost plugs leaking at the back of the engine is it...due to the pressure when the thermostat stoped working,,,probably a long shot though,,,,

Posted on Apr 21, 2009

  • pdshoto Apr 21, 2009

    its hardly one of the frost plugs leaking at the back of the engine is it...due to the pressure when the thermostat stoped working,,,probably a long shot though,,,,

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Some BMW, Volkswagen and Audi cars have a common problem that the water pump impeller becomes dislodged from the input shaft of the water pump leaving the water pump looking ok from the outside, but failed on the inside. If your car experiences this problem it will over heat rapidly much like a thermostat failure. For exact specific repair procedures for this repair visit our online repair manual page.




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