E46M3 - Cooling Concerns / Questions (need help)
 

I have an E46 M3. Recently I discovered that the water temps have been rising towards the RED zone on the gauge when during under high revving conditions. I do occasional DE events so mostly I am experiencing this while running the car in 2nd / 3rd gear; however, when I get on to straights and up shift to 4, you can see the temps fall fairly quickly.

This started during a DE event last year in September. Prior to that, I had never seen the temp rise above the dead-center midpoint on the stock gauge.

That said, BMW has looked at the car 3 times and they cannot duplicate the issue. I am looking for assistance here as I am not comfortable with the response I am getting from my dealer.

I was event able to duplicate the issue on the street while bedding my brakes in 70 degree temps. I did 6 – 8 quick accelerations from 10 – 60 – 10 and I noticed that the water temp needle moved slightly towards the red zone.

I am not sure where to start. I am being told that it could anything from the thermostat, water-pump, radiator or the fan clutch.

Recently, a fellow M3 owner asked me to the cardboard test to see if the fan clutch is working properly or not. I started the car, had my sister rev and hold it at about 2500. I took a piece of cardboard and touched the inner radiator fan and surprisingly it stopped without much force at all. As soon as I moved the cardboard away, the fan started to slowly spin. What are you thought on this? Is the fan supposed to respond this way?

Other than this, what other tests can I do to verify the various components?

Any help / guidance would be greatly appreciated as I am completely lost.

If its a mechanical fan then clutch is absolutely bad, based on that test.

Even with a bad fan clutch though there is no reason you should overheat on the track at a DE. The primary fan is only effective below 40mph otherwise the natural air flow is faster than the fan speed. I replaced my primary with an electric and it can me turned off while on the track with no effect on temp. Maybe your DE's are lower speed.

Replace the fan clutch but keep VERY careful check on the temps once it moves off TDC you are minutes away from a new head gasket or worse.

your fan clutch operation is normal. I would not replace the clutch yet. first look for things to be blocking air flow through the grille. then if you want I would change the thermostat. it is possible it is getting hung up occasionally, alothough unlikely. you can also check to make sure the water pump is working properly. after you start your car you can remove the coolant tank cap and make sure there is a little stream of coolant coming from the side.