325i viscous engaging too early

[terribletaj]

Hi

I'm having problems with my 325i viscous fan, after finding out one of the previous owners had fitted the wrong fan resulting in it smashing against the radiator, I have replaced it with a proper m20 one and it all clears fine. Now it seems that the viscous coupling engages far too early and wont turn off resulting in my car sounding like a jumbo jet for the rest of the journey. It kicks in approx 8 minutes after starting, and the temp gauge is only at the first white mark. Surely this isn't right?

I have tried 3 viscous couplings now, 2 brand new and 1 used but worked fine on the car it came off, all have done he same thing, so this makes me think theres something up with the car but don't know what.

Any help would be most grateful.

Thanks

[Brianmoooore]

The viscous coupling is locked by hot air coming off of the centre of the radiator. With the temperature gauge where you say it is (about 80 degrees), there shouldn't be any possibility of any part of the radiator being hot enough to lock the coupling.
I can't think of anything to suggest, or have heard of a situation like this before!

[Andyboy]

Is the fan blade bolted correctly to the coupling, and the right way around?

[BenHar]

I have heard of new ones doing this to start with and the freeing off after a bit of use.

Ben

[terribletaj]

Hi,

Yeah I know it makes no sense, only thing I thought was that the gauge is under reading but as the fan kicks in only after 8-9mins after starting I don't think the engine/radiator would be hot enough to make the fan engage that soon?

When I got the car it had no thermostat fitted so never warmed up, I fitted a 80c rated one and now warms up fine but makes the fan kick early aswell. I guess thats why it was removed in the first place.

Was thinking of doing a electric fan conversion but would rather sort it properly than have to resort to that.

I found this thread which is the same problem as mine, but a new viscous didn't solve it for me:
http://www.bmwland.co.uk/forums/viewtop ... 5&t=122379

[terribletaj]

Is the fan blade bolted correctly to the coupling, and the right way around?

Yes I believe it is, it only seemed to fit one way round

[terribletaj]

I have heard of new ones doing this to start with and the freeing off after a bit of use.

Ben

The used one does it aswell, all 3 couplings have had around 2 weeks daily use each and didn't improve, maybe I didn't leave it long enough?

[bmwbmwbmw]

This might sound funny but I had the exact same problem on my e39, the fan was constantly on after 10 mins of the car turned on regardless of driving it or not, I swaped it for a brand new one and the problem was still there, after pulling the remainder of my hair out I found that my temp sensor was no good, after changing both of them than I noticed the system had air locks, after bleeding the system the problem had gone away, I than swaped the new fan clutch with the old one and it was perfect, it might not be the same problem on yours but it is worth trying, I hope that helps

[Brianmoooore]

In normal driving, the viscous coupling should never engage. Time for some experiments!
Blank off about a 10" circle in the middle of the radiator from the front, and see if that has any effect on the problem.
Buy a temperature tell tale adhesive strip in a suitable range, and stick it to the centre of the coupling, to see what temps. it does reach.
Get the use of an IR temperature meter to see what temperature areas of the radiator are running at.

[terribletaj]

Hi,

I tried blocking off a section of the radiator but didn't make a difference, I took off the viscous today and drove about for awhile, the gauge went up to the 3rd white line when sitting in traffic so I think my gauge is working ok.

Going to try and bleed it again and get hold of a IR temp meter at the weekend and see whats going on there.

My old e30 318is never got hot enough to engage the fan unless sitting in traffic for ages, where as the 325i is on all the time. Could the water pump have an effect on this?

Not sure what else I can try.

[DHFiS]

Does the rad still have the plastic fan shroud fitted?