m42 overheating?

[keada714]

I just found the aux fan.. The fan turns on when I press the AC button but will not turn on when the car is warmed up.. So i'm guessing my sensor is bad? Also I can easily stop my clutch fan when it is warmed up. So I'm guessing that is also bad. Thus causing the car to get too hot while sitting idle since the fan is slipping..? This is looking good!! making progress!! Can someone confirm this please? I'm heading to work and will work on it once i get off!! Thanks again

[bmwm42]

Replace clutch and temp sensor I would also replace the thermostar seems like it's stuck

[Nairb]

I agree with KenC that you could still possibly have an air bubble. I have had cooling problems since I bought my car, but I have recently COMPLETELY taken care of all my problems.

1. Try and "back fill" the head by putting the coolant into the upper radiator hose. (Disconnect it from the radiator, put coolant into the hose. Make sure heater is on FULL HOT.) You will notice that the coolant reservoir is filling up, as well as the upper radiator hose.
2. Reconnect the hose, and remove the radiator cap.
3. Start the car, and go back to the driver side of the car.
4. Gently pull on the throttle cable, and you will notice the coolant in the reservoir "chugging" down.
5. Add more coolant to reservoir, and again pull on the throttle cable (2-3k RPM.) If it continues to "chug" down, then keep adding coolant. If it does not, add a little more coolant and replace the cap.
6. Drive around (with your coolant in the car) until the thermostat opens, stop car and check the coolant level. If low (it probably will be), add more coolant and continue to drive around until the coolant level does not continue to go down.

Make sure to check that the BOTTOM of the radiator is hot (I usually just use my hand.) If it is not hot, then you either have an air bubble somewhere in your lines, or you have not fully warmed up your car.

Another thing that I have used to check FULL SATURATION of the coolant system is removing the radiator cap when the car is fully warmed up, leave it running, and pull on the throttle cable (1.5-2k RPM max, you don't want to get sprayed with hot coolant.) You should notice coolant shooting out from the top of the radiator AS SOON as you start pulling on that throttle cable.

I have done this at LEAST 5 times in the last 10 months.. spent a lot of money on coolant. I only use 100%, just as a preference. I have replaced every coolant hose, thermostat, thermostat housing, water pump did not need replaced. As previously stated.. I replaced my radiator 2 weeks ago and I have absolutely no problems anymore. My radiator was just not 100% sealed, plastic had begun to warp and my cap was not tight anymore.

Hope this helps.

[keada714]

Hey does anyone know what that sensor is called? Also should I replace the thermostat again? I just replaced it.

Nairb. I dont think its air in the system. my aux fan isn't kicking in unless i hit the AC switch, also I can pretty much stop the clutch fan wehn the car is full warmed up and running.. Which I dont think is a good thing right?

[tonywonder]

the sensor is called a temperature switch. when the cooling system reaches a certain temp the switch activates the aux fan. its part number 61311378073.

and you will need a new engine fan assembly or new fan clutch.

use realoem.com for part numbers etc.

you can order from BMAparts.com or pelicanparts.com BMA is located in burbank.

[selturk]

Yes you shouldn't be able to stop the fan when the car is fully warmed up. Replace your fan clutch or go with an electric fan conversion. Here is the link for it:

http://www.m42club.com/forums/showthread.php?t=70

[keada714]

So i'm free tomorrow and i'm going to be tackling this task tomorrow. Should I just replace the fan clutch and temp switch with a lower degree switch. Or should I go look for an e36 electric fan and wire it up to the original aux connection?

[keada714]

Hey guys,

I was wondering would the aux fan for the m42 be sufficient to keep the car at the normal operating temperature.. I'm trying to do a fan delete and also diagnose my overheating problems. What I did right now was jump the aux fan for high and let the car warm up. The car is still between the 1/2 and 3/4 mark. But once again when I rev the car up to 3-4k the car drops down to a little over the 1/2 mark. any other suggestion. I will be getting the clutch fan as soon as fund will allow me to.

[Ryann]

Make sure to check that the BOTTOM of the radiator is hot (I usually just use my hand.) If it is not hot, then you either have an air bubble somewhere in your lines, or you have not fully warmed up your car.

OR your thermostat is not opening when it's supposed to.

But once again when I rev the car up to 3-4k the car drops down to a little over the 1/2 mark.

With your mechanical fan and shroud installed or no?

[keada714]

I'll check the radiator to let you know if the bottom is hot or not.

So i wired the aux fan to turn on all the time. I let the car warm up and it still stays around the 3/4 mark. But when I rev my car with the bad clutch fan and shroud on it drops a little.

[KenC]

Even with no fan, your temp shouldn't be wildly fluctuating between 1/2 and 3/4. Make sure your heater core valve is open when you're bleeding it.

I think you either have air in the system still or a bad water pump. I'd bet the former though. You could also be just low on coolant.

Efficiently bleeding the M42 takes some experience. I had to do it last night after changing my thermostat.

[jrobie79]

Yeah, i would bleed the coolant multiple times, drive around do it again, and repeat, try to elevate the front of the car a little bit so its at the highest point and keep the heat on full tilt

[KenC]

Just FYI, on the HVAC you want to have the temp selected to high and the fan off.

[keada714]

Thats what I thought. The temp is still high even with a bad fan. Can you guys tell me how to properly bleed this car.. I've bled it many times and I rarely see any bubbles. But I'm going to do it again

[KenC]

Jack up the front of your car.

Take off the cap and bleed screw.

Turn temp selector to high heat (fan off).

Fill with coolant mix until the reservoir is nearly full.

Put cap and bleed screw back on. You need a closed system, or your coolant will boil.

Turn car on and warm up until thermostat is open (radiator return hose will begin to fill and get very warm).

Give your car a few good revs and slowly open the bleeder screw. Close and repeat a few times until you have no more air bubbles. Sometimes you have to rev it quite a bit to force some of the bubbles through.

Let your car cool off completely and assess coolant level in reservoir (there is a cold fill line).