Overheating after coolant change & electric fan

[flipdsm]

I have 2 problems, I swapped over my main fan to an electric fan, I took out the radiator and filled it back up with coolant through the overflow. It now overheats to the 3/4 mark until I shut it off. My heater doesn't blow hot anymore and it used too. I have been opening the bleeder screw on the thermostat housing to bleed it and refill with coolant but for some reason it still overheats. I also keep the heater on full blast when the engine is running to get any air pockets out of the heater core. What is the proper way to bleed this car?

My second problem is my electric fan is only a 1 speed fan with 2 wires. I wired it into the AUX circuit but the fan only turns on when I press the A/C button, that's it. I tried swapping wires where it connects to the 3 prong AUX connector but then the fan won't turn on at all. Anybody have a schematic of the AUX fan circuit? My car still overheats with the fan on.

And just to clarify, my car never overheated at all before I started to tinker with it

[flipdsm]

Would a bad AUX fan temp switch or relay allow the fan not to turn on high/low speeds but still turn on when you press the A/C button?

[jlevie]

The overheating problem sounds like air in the cooling system. The fan only coming on when the A/C switch is pressed sound like a bad temp switch, of it could be caused by the air in the cooling system. Bleed the system by:

1) Using ramps or a jack get the front of the car 1' or more higher than
the rear. That will make the radiator and bleed screw the highest point
on the engine and facilitate removal of air.

2) With the bleed screw open, add coolant until no more air comes out of
the bleed.

3) Leave the filler cap off, or at least loose, and set the heat for max
temp and fan speed. Leaving the cap loose will prevent air that's still
in the system from causing a "coolant fountain" once the engine heats
up. Start the engine and allow it to warm up to operating temp. As it
warms up occasionally crack the bleed screw to release any air and top
up the coolant as necessary.

4) Once the engine is at temp bring it up to 2000-2500 for a few seconds
several times. Then crack the bleed until no more air is released. At
this point the heater should be throwing lots of hot air, which
indicates that the heater core is filled with coolant. You may have to
repeat this a few times to get all the air out.

5) Drive the car a bit, allow it to cool back down, and recheck the
bleed for air. Over the next few days you may get very small amounts (a
few bubbles) of air out of the bleed screw.

[Dude]

Sounds like it needs to be bled more. Also recognize your more likely to overheat if your idling rather then doing 60 on the highway.

[flipdsm]

The overheating problem sounds like air in the cooling system. The fan only coming on when the A/C switch is pressed sound like a bad temp switch, of it could be caused by the air in the cooling system. Bleed the system by:

1) Using ramps or a jack get the front of the car 1' or more higher than
the rear. That will make the radiator and bleed screw the highest point
on the engine and facilitate removal of air.

2) With the bleed screw open, add coolant until no more air comes out of
the bleed.

3) Leave the filler cap off, or at least loose, and set the heat for max
temp and fan speed. Leaving the cap loose will prevent air that's still
in the system from causing a "coolant fountain" once the engine heats
up. Start the engine and allow it to warm up to operating temp. As it
warms up occasionally crack the bleed screw to release any air and top
up the coolant as necessary.

4) Once the engine is at temp bring it up to 2000-2500 for a few seconds
several times. Then crack the bleed until no more air is released. At
this point the heater should be throwing lots of hot air, which
indicates that the heater core is filled with coolant. You may have to
repeat this a few times to get all the air out.

5) Drive the car a bit, allow it to cool back down, and recheck the
bleed for air. Over the next few days you may get very small amounts (a
few bubbles) of air out of the bleed screw.

Wow, that was some good help right there, thanks a bunch. And you were right about the temp switch, I traced it down to that, and sure enough it's faulty.

[CorvallisBMW]

OK here's how the aux fan works:

It has 3 settings. Off, 90C (low) and 92C (high). If you wire it up to the high wire, it will come on at 92C AND when you turn on the A/C. If you wire it up to the low wire, it will come on when you reach 90C and NOT when you turn on the A/C.

You either need the 318ti temp switch (80/88C, p/n 61-31-8-361-787) or a 3-speed resistor for your fan

http://www.spalusa.com/store/main.aspx?p=itemdetail&item=20601003

See my thread here:

http://www.r3vlimited.com/board/showthread.php?t=179952

Note, it applies to all e30s, not just m30 swaps.