Question about 1994 BMW 3 Series
Did you ever replace the thermostat? If it is stuck then it would also cause overheating...Excessive exhaust backpressure because of a clogged catalytic converter could also cause overheating..Also check belt tension and condition. A loose belt that slips may prevent the water pump from circulating coolant fast enough and/or the fan from turning fast for proper cooling...Another thing it could be is a faulty Water pump -- Any wobble in the pump shaft or seepage would call for replacement. In some instances, a pump can cause an engine to overheat if the impeller vanes are badly eroded due to corrosion or if the impeller has come loose from the shaft. The wrong pump may also cause an engine to overheat. Some engines with serpentine drive belts require a special water pump that turns in the opposite direction of those used on the same engine with ordinary V-belts... Also check the Fan -- With mechanical fans, most overheating problems are caused by a faulty fan clutch, though a missing fan shroud can reduce the fan's cooling effectiveness by as much as 50% (depending on the fan's distance from the radiator) which may be enough to cause the engine to overheat in hot weather or when working hard.
Posted on Apr 18, 2009
I'd first, replace the thermostat. It's inexpensive and easy enough to do. I hope this helps you... Good luck!
Posted on Aug 28, 2009
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Posted on Jan 02, 2017
SOURCE: my car is overheating
The expansion tank is a common failure area and its good that you replaced it, however to my knowledge the thermostat is not located inside it.
I would first add the recommended anti-freeze/water combo and fill it up while the engine is running. Close the cover to the expansion tank, but open the bleed screw to insure that the air escapes from the system. You must do this while the engine is running and warm. You may need to add water/anti-freeze. This insures that you get all of the air out of the system and prevents a vaport lock condition that will cause the system to overheat.
If that doesn't work, then you may have a bad water pump, thermostat or both. Its common practice to replace both at the same time. If its been more than 45-50k miles since they were serviced, I would replace both, replace all the belts and hoses and replace your water/anti-freeze at the same. After its all put back together, perform the steps in the second paragraph again.
You can get a good DIY here:
Good luck - I hope this helps!
Posted on Jun 30, 2009
Most BMWs with the M-50/52 series engines(this is the one with all the black covers, 24 valve type) overheat for one of a few reasons. Most common, the coolant leaked out, and now the car can't circulate coolant to cool itsself off. Second, air may have gotten into the system and you are experiencing what is called airlock. This is where the water pump has air in it, and can't push water. You fix this by running it for a bit to make it warm up and pressurize, and bleed the air out using the bleed screw on the radiator; it's right on top. Next problem you can run into, is the water pump may have gone bad. BMW make the bright decision to put plastic impellers on their water pumps, which would break, and not pump water. If this is so on your car, order one that you KNOW is metal, and get the problem out of the way. Make sure that you have the air out of the system before you try to drive it anywhere, or it'll overheat anyways. Finally, and least likely, is the head gasket. Usually these engine will fling oil all over the inside of the engine compartment before they will overheat due to a head gasket. Hopefully this helped you out, and if you have any additional questions, comment on it, as I check back to make sure they're solved.
Posted on May 01, 2010
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