Viscous fan clutch not disengaging fully - adjustment ?

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relaxedcruiser

relaxedcruiser

SILVER Star
Joined
Apr 28, 2016
Threads
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Location
Opotiki,Bay of Plenty New Zealand
Hi guys,

after extensivly searching the web and this forum for answers without sucess I´ll ask this question:

The fan clutch on my 12ht is not disengaging fully. It´s not locked either - its fine until approx. 2000 rpm then I can hear it starts howling which is at around 100 km/h. It's absolutely unnecessarily that the fan is working at all - bearing in mind that it is Winter right now over here and there is plenty of cold air blowing through the radiator. The temp gauge is always at the first mark and I have never seen it above middle position.
In the web there is a lot of guessing of how the fan should work.....
I´ve read many threads about fan mod's to make it cut in earlier, but none to adjust the cut out temp.
On other vehicles I owned and through long experience as a mechanic I know that viscous fan clutches are set up differently, some are stiffer others free up completely. I want mine to free up completely - A good sign of a clutch working like this is that the fan keeps on turning for a wee while after the engine is switched of during normal operating temperatures. My one is turning quite freely when the engine is swiched off but only for ...let´s say half a revolution...
My one seems to be always the same - it´s also not locked for the first turns when cold like others.
I just want it to disengage when not needed - it will help to reduced fuel consumption, noise and power drag.
So - is there a way to make it behave like I want it to?
Less silicon fluid ?
Alter the bimetal spring ?
My one has the blue flange, I have annother one this has a red marking somewhere and it´s even stiffer.
I don´t thinks that it is damaged or not working properly - but still want to change the characteristic.
Anybody with experience in this case ?
 
Very unlikely you'll be able to modify it to your liking.
Buy a new one if it bothers you that much. But there may be nothing wrong with it.
 
Just went thru this, put a new OEM FC on 20,000 miles ago/10 years ago. Sometime in the last few years it started to stay locked longer than it should, not locked up, but never seemed to fully disengage. It would make my water pump blet squell at 2500-3000rpms in 1st or 2nd gear.

Bought a new Aisin from Amazon for $70, it's now working like it should, mpg went up 1mpg, and it's way more peppy, feels like I had an extra 2000 lbs dragging behind me.
 
you could do that, but I messed with the fluid in these things years ago(I think I was the one that found Toy sold the fluid, many many years ago)

but never was happy with the results, I'd just get a new Aisin and call it a day

not sure why mine would have gone bad in 20,000 miles, but the 60 did not get driven for a few years, wonder if they can go bad from sitting? my wild ass guess is the temp sensing spring may have gone bad
 
I would just get a new fan clutch and be done with it.
 
Landpimp said:
Just went thru this, put a new OEM FC on 20,000 miles ago/10 years ago. Sometime in the last few years it started to stay locked longer than it should, not locked up, but never seemed to fully disengage. It would make my water pump blet squell at 2500-3000rpms in 1st or 2nd gear.
Click to expand...

Crap, mine is doing this too. I thought it was just a loose belt. I stay off the gas to prevent squeal at those rpms. My mileage has stayed consistent, so maybe I'm lucky and it's just the belt.... I hope.
 
drove me nuts, seeing how every part of the cooling system had been gone thru, a bad FC was not something that really crossed my mind, but sure enough that was it. I realized it after I drove another fj60 that had just had the FC replaced....it was one of those "doh" moments. I replaced the belt twice in the last year......each time is was worn down. Now, even with AC cranked, no squelling belt and its way more fun to drive. I had a FC lock up 100% on a 80 series, had FC that were worn out and did not lock up much at all, but this one was odd. I kinda figured it was locking up more than my 82fj40 because of the AC on the 60...but now they both work just the same.

what really was wierd was even when I let up on the gas and coasted in gear....it felt like there was something holding it back, now....in gear and off gas.....darn thing just coasts along and I end up using the brakes much more. When I hit the freeway after I changed the FC, I was driving along at 60mph, I punched the gas....and looked down and I was doing 75mph in just a matter of a few seconds....my 1st thought was the speedo was slipping somehow......but nope it just hauls balls now.
 
@Landpimp I'm probably going to wait a while on mine. It's summer here in Texas and I don't mind having a "working" fan clutch when the heat index is over 100 degrees. Forgot to add before, I have driven my 60 less since putting that new one on. Interesting to think about. Can't remember how long ago it was though.
 
I'm glad you guys are talking about this because mine has been doing something of the same thing here lately with the belt squeal and in the back of my mind I've been wondering about the Fan Clutch but didn't want to spend the money on one if that wasn't going to fix my issue. Now, I may just go ahead and buy the Aisin from Amazon and be done with it. It's always seemed to be sluggish on take off when everyone else tells me it should be fairly torquey on low end...Mine has never been what I would call torquey...ever. So, I think I'll go ahead and check this out. Thanks...
 
Well, thanks for all the ideas regarding my fc. Actually mine is not dragging that bad, no squeling belts and the like....and I do not think that it is in bad state of order at all. Just wanted to alter the characteristic. I have driven with fc´s who cutted in and out not unsimilar to an elctric fan - long uphill with all the available horses - fan cuts in after a while - but would as well cut out during the same uphill after the temperature in the rad had dropped to an certain point. I like this.
probably not the case with my cruiser as with ac and pto winch....will look into the parts catalogue if they had different ones - never heard of it though. (After reading through all this fc-treads)
I´ll try and see whether the spring allows the shaft to go to it´s cold-end position.
Happy cruising !
 
Hi guys,

I finally got around to deal with this fan clutch and took it apart yesterday night. And its working again like it should !
Although having repaired/rebuild a lot of engines / gearboxes and the like in my life, this was the first time to open a fan clutch.
After seperating both halfs everything lokked quite clean and alright...but the blades that control the fluid flow through the designated slots where well past them. Actually about a quarter of a turn. And this in an ambient temperature of 8°C. (46°F)
What happened was that the bimetal spring was wind together like it would do when heated up.
After carefully opening it up again it was back on it´s cold end stop rest.
The following test brought a fat grin into my face when I heard that the clutch disengaged after a very short while after starting up.
I have still to adjust the inital engaging temp a little to the hot side by preloading the spring a bit more against the cold end stop.
Right now the clutch engages when the needle is moving just a tiny lttle bit up from the point where it´s sitting normaly...this equals to about 78°C. temp at the thermostat housing outlet towards the rad.
The fan clutch was therefore always engaged before - but with a lot of internal slip. To alter this is discussed a lot in the web.
I do not know whether this is a common fault when they get older, perhaps one of the previous owners twisted the spring to make the clutch always engaged. I have another clutch with the same behaviour - I´ll open it soon and make some pictures which I have forgotten while doing the enthusiastic researches yesterday.
To just open something (instead of buying new straightforward), hunt for the faillure, alter things and discover that they work like new is what gives me the most satisfactory moments when playing in the mans cave.
The whole thing has of cause still to show a bit more longterm reliability until it can be stated perfect.

Just to let you know...

Happy cruising !
 
Very interesting, let's see the procedure on the next one.
I feel mine is a bit active, mostly on.
In the winter, my previous fc spun freely after two minutes of idling, and would let the temp rise to normal before slowly going on and off, which was great.
The one I have on the 12HT runs a lot more.
 
Hi TLC - it would be quite interesting if the bimetal spring winds itself towards "hot" when ageing. My one was a bit rusty... Nearly all the discussions in the web are about fan clutches which engaging to late or not strong enough.
I forgot to mention that the engine, due to less drag from the fan, runs significantly stronger and easier from 1800 right to 3000 rpm. Before it was always somehow unwilling to rev higher than 2000. After stopping the engine in normal running temperature the fan turns absolute free for a while now. It seems that the only drag is from the Oil seal and the bearing, which is great.
I got my cruiser only this January....unbelieveable that I drove the 10.000 km since then with this brake at the front of my 12HT.
Well, the nature of this great engine makes it that you normally don´t need to rev a lot past 2000 rpm.
Most certainly the fuel consumption will drop also......if I´m not tempered to enjoy the "new" free reving engine to much.

cheers....
 
Hi folks,
just read through this oldish thread - and with some satisfaction I can report that my fan clutch is still working fine - thats about 9 years and 160.000 km / 256.000mls ago so it can be well worth taken them apart and alter their settings.
 
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