bureau13

My temps are going up fairly rapidly now when I'm sitting at idle. It has always done this to a certain degree, but it seems significantly worse. And sure, it's hot here in the summer, but still. It's worse now than, say, July, and I don't think it's hotter now than in July.

The thing is, as soon as I start driving again, it cools right down. That tells me (I think!) that the radiator, water pump, etc are all doing what they should. Airflow across the radiator is insufficient at idle. (If there is another likely cause, please let me know).

I'd like to confirm that it's a bad fan clutch before I replace it, however. If it's working properly, I should see a significant reduction in resistance to me turning the fan by hand (car off of course!) when it's hot as opposed to on a cool engine, right?

Mrmerlin

if your engine is running at idle and the fan clutch is working properly ,
you will hear the fan start speeding up and a good draw of air come out from behind the fan,
then it will stop making air as it cooled down
If your noticing that the cooling system isnt keeping things cool then its time for a new fan clutch.
google Porsche 928 fan clutch

jpitman2

And get ready to sit down! You could try refilling the clutch - Toyota viscous silicon can be bought in small bottles. Best way to get it in is a small syringe to force it in - dripping will take forever. I tried it once, but it was all spat out quite quickly, so I went electric - 2 11" SPAL in one housing.
jp 83 Euro S AT 57k

Mrmerlin

after you google this you might find that a Range Rover fan clutch can be made to work on a 928 with minimal machining work, and they are quite reasonable in price

bureau13

Unless it was an old post, I think there is a "Uro" fan clutch that Roger sells? Is the Range Rover clutch better?

FWIW, I could feel no difference in resistance between hot and cold on my car, which I think supports the "fan clutch bad" diagnosis...

Mrmerlin

sounds like a new fan clutch is in your future,
it is clear if its working well or not.
I didnt find that thread about the RR clutch mod

jpitman2

The Land Rover clutch works like this:- Fan ETC1275, Viscous ETC1260. Fan is 11 blade, 17" dia. Take a broken 928 viscous, knock the viscous off the shaft completely. Get a dead discovery water pump and cut the LH threaded part off the front. Machine down the front of the 928 shaft so its a press fit into the LH threaded adaptor. End result looks like this:-
Attachment 1349258
If you find a used fan, check it carefully for cracks in the blade roots, as they tend to break in hot climates, and you dont want to shed a blade, even in nylon!
Worked for me in Saudi, but have since gone electric.
See also
https://rennlist.com/forums/928-foru...an-clutch.html
jp 83 Euro S AT 57k

Landseer

Nice solution.

if you go the refill route, try a small syringe, jam fit a basketball fill needle to the end. You remove the little plate from the fins that covers the fill hole. Insert, you feel a little spring loaded check valve, shoot the stuff in.. if lucky, the little seal will still work. Use silicone gasket former to cement the bimetal plate back in place. It operates an internal clutch when it senses heat.


Three sources of liquid are Toyota parts dept, rc hobby store for filling differentials on rc cars., and the household products industry. Another use is in spray wax formulations for furniture and floors where it takes place if, or augments, wax.

Chemical is dimethicone, basically a linear silicone polymer and its designated by its viscosity in the name, ie, dimethicone 100000 cp. It's chain length determines viscosity. These fans take a thick one, between 5000 and 10000 centipoise. Suppliers in the USA are Wacker or Dow Chemical/Dow Corning, but they probably won' sell direct. Value is about 2 dollars a pound. Last time I bought the packaged Toyota product was 10 years ago for filling fans on then-old toyotas and it cost 20 dollars for a tiny tube and the parts guy struggled with finding it.

That said, method was successful for me filling 2 fans

Speedtoys

Well...its not as simple as squirting it in...where is it going to _go_?

The air that has replaced the old fluid, has to also get out.

This is where heating it with a heat gun, while spinning it..helps move the fluid IN the assy to the edges while heating/expanding the air IN it. Then, you keep spinning it and let it cool (I use a fan to blow on it as I spin it) and you simply drip new fluid at the hole where the plunger used to be, and the cooling air in the clutch cavity pulls in the new fluid..and again the spinning quickly distributes it to the inside edges. A good table fan aimed well will spin it fast enough as you apply head with the heat gun...and then let it cool...so that all you have to do is heat it up (but not TOO horribly much, maybe 150-160d tops) and then the fan cools it down too.

Do this until...full. And when heated no more air bubbles out.

It's not as simple as pushing in new fluid, you have to replace the air trapped in it, and use heat to push it out, and likewise pull in new fluid during cooling.

Landseer

What I did worked at the time.

But you've reminded me it was slow-going.

Your way makes much more sense.

Speedtoys

Ya...let expansion/contraction and a fan to both spin and cool it...and no prep other than cutting the end off of the tube it came is is needed.

It will 'breathe' a LOT..and likewise suck in a lot, in a 5min heating/cooling cycle. There will be a marked difference in how well it spins (tighter = better) once you are done.

The issue is obvious..if it leaked out once, it will again. Ive seem some come back out fast, others slow.but none have been "clean" and leak free after a few months.

bureau13

I actually bought some fluid a while back. It's...somewhere. However either of the solutions discussed here...modifying a Land Rover clutch, or going through this refill process, seem like a lot of effort when there's a sub-$200 aftermarket solution*. What am I missing?

*I'm not 100% sure this solution is still available, I've sent an email to Roger...

ROG100

Adding viscous fluid was the only economical option if you did not want to pay circa $700 for a replacement fan clutch. I used replacement 10k CS fluid in a couple of my clutches. Worked in one but the other leaked out after a short period of time.
I now sell a new direct replacement fan clutch for $195 - fitted that to the 86.5 where the fluid leaked and WOW what a difference.
New clutch for me every time.

bureau13

I'll take one please :-)

SteveG

For any other following here: It's been mentioned in other threads; the fluid exited for a reason, it most likely didn't dry up. Even if it did, why? I tried the syringe method and like other poster, it immediately exited the spinning fan and smeared in a 24 inch spin art pattern. If you don't fix the reason it went dry, you are wasting your time.