I've searched as many threads as I could read before posting this one.
So my cooling fan was not coming on, checked fuses and all seemed OK.
I installed a new fan and same thing, it doesn't come on when the engine heats up. I disconnected the fan wires and tested it with some wire leads and both low and high speeds are working fine.


I know when you turn on the AC the fan should also come on but I have since removed the AC compressor and installed an idler pulley since this is mostly a track car.


On another issue (maybe related) I cant seem to get the coolant to bleed properly, don't know if the two are related or not. I can remove the bleed screw on the upper radiator hose completely and see coolant rushing by but it never gets high enough to purge out the air.


water pump? thermostat? temp sensor? I'm at a loss and ready to bring to a garage.

 

Might be able to take a look at our tech articles and see if you can find anything that might help you out. If you cannot seem to find any help, you can also give us a call and speak with a specialist. Good luck with resolving the issue.

-Luccia

 

You said the fan does not come on when the engine heats up. Heats up to what temp? How hot does your motor run? Motor on

 

before I disconnected the water temp sensor, which is now in the upper radiator hose bleed screw hole, it got to about 240. so the thermostat is opening and letting coolant into the radiator but no fan.

 

The fan kick on with the A/C on , think high speed and when you have been running the car hard or in high temps.

I would check those wires and plugs. Check that temp sensor in the head. Sounds like its bad or something. But if the coolant does not reach the sensor because of air, that might be an issue. Did you change the coolat or have a leak ?

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checked wires, plugs, fuses, relays. I did loose some coolant when I replaced the cooling fan but think I finally got the air to purge out of the system today. I am at a total loss on this one????


only thing left to do is replace the temp sensor, if that doesn't work I'll be hardwiring a 2 speed fan switch and mounting it on the dash.
don't know what else t could be.

 

Yea, if all those are ok , I would double check the plug going to the sensor and see if maybe a rodent chewed a wire or that wire going to it, then replace that sensor.

 

i dont know if you already found a solution to this issue but...i have an 03 mcs and had the exact same problem. My cooling fan did not turn on at all, which led to overheating the engine. Took it to a shop, long story short, they replaced other **** including a new fan, thermostat and housing...which didnt fix the issue at all. i did some reading, found out that the wiring for the rad fan is in the same circuit as the ps fan. I knew that my ps fan was seized so i checked the fuse...It was blown. So I replaced that fuse and the ps fan. Rad fan works perfectly again. I believe there was a recall by bmw for this, they separated this circuitry.