Fan Clutch

Article by: Johan

Article applies to: all BMW models with a viscous clutch cooling fan.

Problem: It’s very easy to spot a bad fan coupling. The engine temperature will rise when standing in traffic.

On my 735i it went to about the 3/4 mark. Apparently the electrical fan on the air conditioning condenser will then be switched on though the temperature switch on the radiator.

With the engine at operating temperature it was very easy to block the fan with a thin unfolded news paper.

After switching off the engine the fan could be made to turn over 10 times by giving it a good swing.

Some people prefer to install an electrical fan when the fan clutch fails.

I didn’t as installing the fan is time consuming and a complete installation kit costs about the same as a new fan clutch.

There might be a small power gain as an electrical fan takes less power from the engine then the heavy fan coupling.

Temporary fix: Somehow critical things that affect the drive-ability always brake on a Saturday evening with no place to order parts until Monday morning.

As I needed the car I welded the clutch to the nut. Well welded might be an overstatement.

As the clutch is made out of aluminum and the nut is made of steel they can’t be welded together.

But you can melt away part of the aluminum so the weld pulls the fan.

I considered leaving the clutch welded for an unknown period of time.

But as there never seems to be a cheap fix on these cars there was a small problem.

The fan ran very unbalanced. I guess melting away the aluminum and adding welds kind of unbalances it 🙂

This fix worked fine for a couple of days but I can imagine the unbalanced clutch will pull the water pump out of it’s bearings.

Clutch replacement:

Put a 32mm box end wrench on the clutch and give it a good whack with a hammer.

Remember the thread on the clutch goes the wrong way around!

Undo the three allen screws that hold the plastic fan blade to the fan clutch and remove the fan blade.

I read on various forums the coupling should be stored upright. But somehow it came from the dealer in a flat box.

Now all you have to do is get it back together again.

Possible clutch repair:

Lots of cars use the same cooling setup with a viscous fan clutch.

So while surfing the net I found a Porsche 928 website with repair instructions for the fan clutch.

Of course I only found this page after I bought a new clutch, but I was still interested in the idea of fixing it.

So off I went to explore the possibility of a BMW fan clutch repair.

First I removed the bi metal plate which is clipped in four places:

I did this rather rudely so I broke the aluminum. But it seems you can fit it back under two new notches.

This exposed a possible filling hole:

I removed the spring clip with a knife blade:

Hey what is that? Clutch fluid!

After removing the metal pin a hole was exposed from which a small amount of fluid still leaked out. Exactly like the clutch on the Porsche 928.

As I already have a new clutch installed there is no need for me to fix this one.

But it seems you can order the clutch fluid from a Toyota dealer and refill the clutch.

As I haven’t done this I’ll redirect you to a write up I found by John Krawczyk which has the entire procedure.

If anybody applies this procedure to a BMW clutch I’d love to hear to results and see some additional pictures which I will of course add to this page.

Parts used and costs:

Yes you are reading that right for a new fan clutch you will have to fork over 128 euro! And that’s without taxes.

Total amount of time: Installing the new fan clutch took about 10 minutes.

Skills needed/difficulty level: For this job you don’t need skills. You just need cash to pay for the expensive new fan coupling.