S50'd M3 heating issue

Post Sun Jun 08, 2014 5:17 pm

So have small issue, i'm pretty sure the fan has stopped spinning.

Normally the fan would kick in when it would go over 1/2 on the temp or when stuck in traffic etc.. it was quite loud and noticeable, I'm not 100% what fan/rad setup went in here as i didn't build it, could possibly be electric?

Anyway driving today was working fine, parked car, enjoyed the sun, went back to car driving home and I notice temps creeping up to the red and no sign of the fan kicking in, heating on full blast to get it home without engine or damage.

fired it up again still no fan etc.. heating again creeping up to red.

I know its really difficult to diagnose without the fan/rad setup but if anyone has any idea where to start that would be much appreciated.

Here's the original build thread, sadly no mention of the fan/rad setup.

http://www.e30zone.net/modules.php?name ... sc&start=0

Post Sun Jun 08, 2014 5:33 pm

The fan is in front of the rad behind the kidney if that helps any deduction of what it is

Post Sun Jun 08, 2014 5:49 pm

Short the contacts on the plug for the thermo switch and see if the fan runs.
Check fuses.

Post Sun Jun 08, 2014 5:58 pm

fuses checked, well the little open ones anyway, one was blown but i replaced it and no difference. Where is the plug for the thermo switch?

Thanks

Post Sun Jun 08, 2014 7:06 pm

In the RH end tank of the radiator if the installation has been done properly.

Post Mon Jun 09, 2014 5:09 am

It depends what radiator / cooling system is in there.

The original m3 fan switch is in the thermostat housing in the pipework between the engine and rad on the right hand side of the bay. S50s have the thermostat built into the coolant pipe on te front of the engine so I doubt the original one is there any more, so the switch is likely to have moved.

It could be screwed into the radiator somewhere or be an aftermarket controler spliced into a hose somewhere.

What speed were you doing when the temp started rising? The fan shouldn't kick in at all in normal driving, at 20+ mph you'll get more air through the radiator through the motion of the car than the fan could ever push through. The fan is really only there to keep it cool in slow moving traffic.

Post Mon Jun 09, 2014 9:31 am

Depends what fan is fitted, some can do as good a job at blocking the airflow than moving air.

I would expect Matt had fitted the switch in the side of the E36 M3 rad

Post Mon Jun 09, 2014 12:55 pm

Stop, start a lot really and then say 15-20 mph, it would obviously go down when driving but it was very hot yesterday, the fan never really kicks in in normal driving to be honest, but the temp shouldn't really be that high on the gauge anyway I'm guessing, even if the fan is not functioning properly, will have a check when i get home and look for the switch

Post Mon Jun 09, 2014 1:15 pm

Right, so I take it this is the switch?

And if it is which of the contacts should I short?

Thanks for the help

Post Mon Jun 09, 2014 1:22 pm

In your pic, short the top pin (which should show 12v with ignition on) to either of the lower pins, the pin on the right should be low speed, pin on the left high speed

Post Mon Jun 09, 2014 1:23 pm

Thanks dan will have a go and report back

Post Mon Jun 09, 2014 1:38 pm

high speed works, low speed doesn't, but I'm pretty sure that might have always been the case but I could be wrong.

What next, I take it the thermo switch turns on the fan when it reaches a certain temp.
I noticed that the expansion tank level was maybe a 1cm or 2 too low just now, not sure why that would make the rad run too cold if the switch us not faulty.

Any suggestions would be most appreciated

Post Mon Jun 09, 2014 1:49 pm

It will more than likely be the fan, the low speed resistor burns out, common problem.

To confirm it, bridge the pin on the switch as above to low speed, then test for power at the fan before the resistor, or at fuse 3

Post Mon Jun 09, 2014 2:44 pm

okay thanks dan will check later when i get back, where is resistor for the fan?

I take it its just a case of a new resistor if thats the case?

however shouldn't high speed have kicked at those kind of temperatures?

Post Mon Jun 09, 2014 3:55 pm

If that rad was the one I fitted to my sport before mat bought it, I got the fan switch from bmw and its the standard e36 m3 one for the 2 speed fan. I didnt realise mat had gave up on his conversion.
So I guess dusty has my old engine then ?

Post Mon Jun 09, 2014 4:37 pm

Yes i believe this is your old engine, Matt sold it to a guy in Spain who I bought it off a couple of years ago.

Thanks for the info, I don't know either way if its the original rad from your car, it is a speed fan switch however.

Post Mon Jun 09, 2014 7:18 pm

Some resistors are separate, some are built into the fan body, if its the E36 M3 temp switch it wont come on high speed until the rad temp reaches 99° which is much too hot!
A temporary fix is to join the two wires to the bottom pins together on the temp switch plug, the fan will come on at high speed at both stages then