overheating problem m50 Help...

[darien18]

im having overheating problem with my 95 525i (m50) so i replace the
water pump
thermostat
fan clutch
radiator

bled the system then let it idle for 2hr with no overheating problem
but once i turn on the fan with the heat it doesnt blow hot air and the temp start
to go up and guys have any idea whats going on?


thanks

[jint45]

heater valve, located under the hood, also check auxiliary water pump its right near the heater valve

[darien18]

heater valve, located under the hood, also check auxiliary water pump its right near the heater valve


just check the Auxiliary Cooling Fan and its working fine

so i need to check the auxilary water pump and heater valve
how do i check if there working??? and it this why my temp goes up?

[LouieD]

You have air in the system. Set the front of car higher than the rear. Turn the temp control knobs to full hot. Set your fan to high. Now re-bleed the system holding the idle at around 1,500 rpm till you get all air out of bleeder and hot air from vents. If you get more air from system, but warm or no hot air from vents, take a test drive. See if you get hot air from vents at engine speeds above 3,000 rpm. If that's the case your auxiliary pump is inoperative. The pump should operate with the key on when the engine has reached operating temperatures. It sits beside/below the brake booster and you will hear it hum. But I have had pumps hum and stop working the moment they warmed up. The tell-tale sign is if you get heat at high engine speeds but not at idle, you have a bad aux. pump.

There is also a possibility that the heater valves are stuck closed, but from what little experience I have that is less likely than a failed aux. pump. The valves normally rest in the open position so for them to get stuck closed it would take a lot of miles with crappy or no coolant (pure water) in a hot climate to seize them in place. Not impossible, just a bit less probable.

Good luck.

[M Quick]

Did you have the fan on and the temp on full heat when bleeding the system? Otherwise that's why you got air in the system. Do what you did but with them on full blast. As you need to get water in the whole system.

[darien18]

You have air in the system. Set the front of car higher than the rear. Turn the temp control knobs to full hot. Set your fan to high. Now re-bleed the system holding the idle at around 1,500 rpm till you get all air out of bleeder and hot air from vents. If you get more air from system, but warm or no hot air from vents, take a test drive. See if you get hot air from vents at engine speeds above 3,000 rpm. If that's the case your auxiliary pump is inoperative. The pump should operate with the key on when the engine has reached operating temperatures. It sits beside/below the brake booster and you will hear it hum. But I have had pumps hum and stop working the moment they warmed up. The tell-tale sign is if you get heat at high engine speeds but not at idle, you have a bad aux. pump.

There is also a possibility that the heater valves are stuck closed, but from what little experience I have that is less likely than a failed aux. pump. The valves normally rest in the open position so for them to get stuck closed it would take a lot of miles with crappy or no coolant (pure water) in a hot climate to seize them in place. Not impossible, just a bit less probable.

Good luck.



bled the system again
heater valve making hum sound
still no hot air at idle
drove the car for a test drive felt warm air from the vent


Did you have the fan on and the temp on full heat when bleeding the system? Otherwise that's why you got air in the system. Do what you did but with them on full blast. As you need to get water in the whole system.



yup full fan/heat on when bleeding the system
how would i know when to stop when no bubbles and air coming out
from the bleeder ?

[LouieD]

bled the system again
heater valve making hum sound
still no hot air at idle
drove the car for a test drive felt warm air from the vent





yup full fan/heat on when bleeding the system
how would i know when to stop when no bubbles and air coming out
from the bleeder ?

I still vote aux. pump is inop. or failing. You have warm air when rpm's are up. At idle the cooling system will not move the volume of water through the heater core to create warm air, hence the aux. pump.

Yes, you bleed until a steady stream of coolant is coming from bleeder screw.

[darien18]

I still vote aux. pump is inop. or failing. You have warm air when rpm's are up. At idle the cooling system will not move the volume of water through the heater core to create warm air, hence the aux. pump.

Yes, you bleed until a steady stream of coolant is coming from bleeder screw.


yes i have warm air when i have it at 1,500 rpm but at idle no warm/heat
so when i replace the aux pump do i need to replace the heater valve aswel

thanks you guys:)

[LouieD]

I don't think so. You have hot water getting to the heater core, just not enough of it at idle... so the valves should be ok.

[darien18]

do you guys know a mechanic that does a head gasket replacment or a shop
i live in the 818 area reseda ca.

Losing coolant and loads of white smoke coming from exhaust so am i right to think head gasket is Going