Water Pump Replaced on 1990 BMW. Now it overheats sometimes.. [Archive] - Bimmerfest - BMW Forums

: Water Pump Replaced on 1990 BMW. Now it overheats sometimes..

Bull City BMW
10-23-2009, 03:32 PM
So I had the water pump replaced on my 1990 535i. Every once in a while the temperature goes up. If I turn the heat on, it goes back to the middle. Sometimes it will fluctuate pass the middle. Before the pump went bad, it would always be in the middle, not one hair over. Any ideas to the problem? Can it be the thermostat?

10-23-2009, 03:39 PM
How much past the middle? When I replaced my water pump it was very specific to bleed the system. Did your system get bleed when you did the pump? The thermostat can be sticking and causing the issue. Was the thermostat replaced when the pump was?

Bull City BMW
10-23-2009, 04:01 PM
No the thermostat was not replaced and idk if they bled the system or not. It wasn't a bmw shop. Maybe I should start taking it to one. I should replace the thermostat anyway...

Bull City BMW
10-23-2009, 04:03 PM
It go into the red a couple of times and the warnings came on. Once I turn the heat on, it went back down.

10-23-2009, 08:30 PM
Definetly change the thermostat. Pretty easy to do and will require it to be bleed again. Has the radiator fluid been flushed recently? Also you need to check the fan clutch. With the engine off does the fan spin easily on it's own or can you feel resistance? If it spins easy when the engine is cold you probably need to replace it.

10-24-2009, 08:40 AM
Did the Water Pump actually fail, or was it a precautionary changeout?
If it failed, sometimes the plastic impeller breaks up and unless you are very careful about retrieving all the pieces, they could be floating around in your cooling system with the potential to block water passages.

Definitely change the Thermostat and do a thorough flush of the cooling system. Make sure you turn the Heater controls to full ON (with the ignition on) before you do the flush. Drill a 1/8" hole just above the arrow that marks the top of the thermostat. This helps the bleed processs and has no effect on the thermostat operation. Also raise the front of the car a little so that when you refill the air will hopefully collect at the highest point in the rad where the bleed screw is. You may still have to bleed the system though once the engine has run for a while.

Bull City BMW
10-24-2009, 12:18 PM
Thanks guys! The main radiator hose had actually sprung a leak, so I waited until the weekend so that I could have the oil changed and the hose replaced at the same time. Well when the hose was swapped out and I drove the car out, it started overheating. I turned around and went back to the shop and the mechanic said the pump had crapped the bed. So I had the car towed to another shop, where they did the work. I'm assuming that they flushed the system out when they changed the pump, or should I not make those assumptions? I think I'm going to replace both the thermostat and fuel filter. I've had the car for 3 years, no problems at all, except for the standard oil changes.

10-24-2009, 01:23 PM
Finding a shop you trust is a tough thing. Never assume they flush your system though. To properly flush and bleed the system takes a couple hours, so a shop would need to charge for that time. Most will probably just change the pump and top off the coolant. Remember they are out to make money. Many shops pay their techs by the job, so if they get the job done faster they can start another job sooner. I know many shop techs and they can often get paid for 60-80 hours in an 40 hour week if they are good and have the right tools to be more effecient.