Rebuild Fan Clutch

[kakacookhe]

Has anyone done this?
I have rebuilt fan clutches on other vehicles. It cost about $15 for the special oil.
The Trailblazer has 75k on it and the fan clutch is not operating like new. A new one will fix it, but Im looking for info on the rebuild as to what weight oil and even if it can be done. Such oil is not described in terms of weight but CST, my other vehicle used a 10,000CST oil. I assume the Chevy would be similar???

 

[TJBaker57]

Has anyone done this?
I have rebuilt fan clutches on other vehicles. It cost about $15 for the special oil.
The Trailblazer has 75k on it and the fan clutch is not operating like new. A new one will fix it, but Im looking for info on the rebuild as to what weight oil and even if it can be done. Such oil is not described in terms of weight but CST, my other vehicle used a 10,000CST oil. I assume the Chevy would be similar???

The most I have done is remove the speed sensor/electromagnet part to have a look inside. A common failure is the fluid control valve but I didn't readily see a way to remove/replace that part.

This thread will tell you about this failure etc.

Fan clutch 101

www.trailvoy.com

 

[kakacookhe]

The most I have done is remove the speed sensor/electromagnet part to have a look inside. A common failure is the fluid control valve but I didn't readily see a way to remove/replace that part.

This thread will tell you about this failure etc.

Fan clutch 101

www.trailvoy.com

When you had it out, is there a way to separate the two halves of the fan clutch? Some are screwed together and some are riveted. The is usually 4 points where it is screwed together.
The common fail, and this is 100% going to happen, is that the oil viscosity breaks down and is not able to turn the fan fast enough, thus lack of cooling.

 

[TJBaker57]

common fail, and this is 100% going to happen, is that the oil viscosity breaks down and is not able to turn the fan fast enough, thus lack of cooling.

I have pulled, examined and engine tested maybe 8 junkyard fan clutches. I have not seen this failure in these model specific fan clutches from Hayden, Behr, R&B Industries (Dorman). The more common failures seen here, and spoken of by the apparent GM employee who wrote the previously referenced thread are fans in which the control valve fails to isolate the fluid in the reservoir and as a result the fan overspeeds.

I have not looked for a way to separate the halves as my primary interest was and is the control electronics.

 

[TJBaker57]

Here is a peek inside an R&B Industries. They used shims to adjust the maximum valve opening.

 

[Mooseman]

AFAIK, the halves look to be press fitted together. And being an electro-viscous clutch, the internals are not available for replacement such as valves, actuators and sensors, which are the failure points of these.

I have seen the others being rebuilt, mostly from Asian vehicles, where only the oil needs to be replaced. These are much more complicated than those thermal clutches.

 

[kakacookhe]

TJBaker has it apart enough to drain and replace the oil wo breaking apart the halves, so that is all that would be needed, and to know the amount to put back in.
Yes, mine was a Japanese truck with simple thermo spring clutch.
Despite any complicated internals, the oil is still the same and will always break down. Most people do not know this I guess. It starts breaking down the very first time the key is turned. Mine is at 75k miles so getting to where that break-down is noticeable.
For at least on the Jap vehicles, and I assume every fan clutch, the fan should roar to life on start up and be loud and blow a lot of air (be at full lock - 70% or whatever it is) and then settle down after 15 seconds or so as the oil spins out where it should be. New cars (circa 2004) do this, ones with some miles on them do not. It sill cools, but stress it in the summer and you see it is weak.
On mine I suspect that it is just the oil. There seems to be no failure going on, it just runs a little hot in the summer with AC on and in traffic, and the fan is not anywhere near its highest speed as when new.

 

[TJBaker57]

the fan should roar to life on start up and be loud and blow a lot of air (be at full lock - 70% or whatever it is) and then settle down after 15 seconds or so as the oil spins out where it should be.

These fans will roar at startup for two reasons. One is if they were shut down while the control valve was open. The second is if they came to rest with the fluid control valve at the bottom.

My original fan clutch had over 280 thousand miles on it when I accidentally fried the solenoid circuit. There was no problem with clutch engagement at the age of 18 years of operation. And the engagement was not judged by sound but by reading the speed sensor via the OBD2 port. As seen here recently... with a junkyard pull

 

[budwich]

I think there is still something fishy about the "startup state". IF at shut down (ie. just parked and getting ready to turn off), and the fan is not "roaring" which should indicate that the fan is not fully engaged, restarting cold thereafter (x hours after) should produce a "non-roar" most times IF the fluid valve position has a relatively small portion of the circle "envelope" to be in. Yet I find, on my 2008, more often than not, the roar is there at startup. The clutch was changed about 1.5 years. The results haven't changed much since replacement and seasonal changes. This is with a thermal clutch not electro-mechanical.

 

[Mooseman]

On my 9-7x with the thermal fan, it always started roaring. I also remember my 02 TB with a thermal did the same thing. My 07 TB with the original electro-viscous clutch does not roar but works perfectly fine at 140k km.

I think it all has to do with which position the fan clutch stops at. If the fan is not perfectly balanced, it will always stop at its heaviest position down. One could try to unbolt the fan from the clutch and move it 180 deg to theoretically move the end position of the clutch when stopped. It would also help if we knew where the valve is inside the clutch.

 

[TJBaker57]

It would also help if we knew where the valve is inside the clutch.

For some manufacturers we can know this. The linked article details it. Has to do with the location of the checkball if present. I actually have my fan blade labelled and currently pop the hood and orient the fan blade/clutch with the valve up for overnight. Mostly for experimental reasons.


For article accessibility:

Screenshot_20211114-083716_Chrome.jpg

drive.google.com

 

[Mooseman]

For easier reading, found the original post on TV:

Fan clutch 101

www.trailvoy.com

Will also post that link in the FAQ as this is very good info.

 

[budwich]

OK... so my question is: how much fluid is actually in the clutch and how big of an "arc" does the valve have in determining when it is outside the "leak in" of the fluid.
I just checked now. The ball bearing was about at 4 o'clock and the "cold start" was quiet... first time in about 4 cold starts. I am going to check this a few more times and perhaps see if Mooseman's theory on where it stops has some merit (ie. heavier side ends up down). IF so then possibly rotating the fan blades a quarter turn (unbolt / bolt) might do the trick or at least improve the chances of a quiet start up.
My problem is access to the engine compartment at start up requires be to push the vehicle out of the garage to get clearance from overhead storage (bikes). Hopefully, a couple of checks will be enough to make a call.