Please pardon me if I am breaking any rules for this Off 5 Series topic, but I haven't gotten any help anywhere. And I always do with you guys..... So please Help.

So my wife's 2005 BMW X3 keeps overheating from time to time. I have checked the fuse, coolant level and even replaced the coolant (yes with BMW coolant 50/50) and bled the system. There are no leaks anywhere. I have changed the thermostat, all the hoses and even the coolant temp sensor. What I have noticed is that when I start the car, sometimes the fan never kicks in and the guage eventually starts to tilt right. I have also replaced the fan with a known good used fan but the problem still persists. PLS HELP!!!

 

The cooling fan is driven directly by the DME via a PWM signal (same as the e60 as it is on the e83).

The DME determines when to turn the fan on based on the coolant temperature reading from the coolant temperature sensor.

It sound like a faulty connection between the coolant sensor and the DME.

Check pins 38 and 39 on the DME x60004 connector to see what the resistance is. It should be something like 2.7k ohms on a cold engine and 900 ohms when its hot.



Otherwise... The DME is farked.

 

Hmm, interesting, do you happen to know where the DME is on the E83? I mean what else could it possibly be? Thanks for your response.

 

I can't imagine what else it could be. Either the two fans or the two temperature sensors are bad... or there is a wiring problem.

The DME is buried under the plastic covers in the engine bay on the drivers side (similar to the e60).

 

This car actually has just one fan to cool everything. The plug has 3 prungs. +, - and a signal from the coolant temp sensor. It is still quite possible that the one single used electric fan might actually be bad. Everything else works fine, what else does the DME control? Might have to actually get a brand new fan.

 

Issue resolved... My "known good used fan" is actually now known to be bad. Replaced the fan with a brand new fan and the fan kicks in immediately the car starts.....

 

Same fan as the e60. Ground, Power, and PWM (from the DME NOT directly from the temp sensor).

Everything engine control related. It's the main brain.

Oops. I suspected that but it was 'known working'