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M923A2 Fan Clutch Repair - Any Clutch Gurus Out There?

Boi

New member
19
9
3
Location
Saint Charles, IL
I reinstalled the fan clutch today and took the vehicle for a drive. This is both good and bad news. The good news is installation was quick and everything was functioning afterward. The "bad" news is that the rattle has diminished significantly, but not ceased entirely. The fan seems to be working very well at this point, blowing nice and strong. The lack of silence is a bit puzzling. I can't say I am disappointed with the result; after all I did nothing more than clean and grease the clutch. I have a hunch that the rattle isn't in the clutch, but perhaps near and related to the clutch. This would be one explanation of why the sound diminished but persists. It might be worth investing in a stethoscope at this point...

I am curious to know what others think about this.
Has anyone taken a stethoscope to the clutch?
 

wrenchturner6238

Active member
Steel Soldiers Supporter
332
29
28
Location
Beaver Oklahoma
A lot of these fan clutches just rattle I know they do also in over the road trucks too. yes you can listen to it with a stethoscope or a long screw driver but be very careful because of the moving parts. you need to listen on the stationary parts
 

jerry v

New member
200
1
0
Location
michigan
Hi Jerryv,

I don't plan on using a new belt. The one that was installed still has a lot of life left on it, so I will replace it when it needs to be. :-D

As for the reassembly:
What I started off with was putting the piston/thrust plate in the housing for the fan. I lightly greased both o-rings and the entire plate and set it aside. I applied a fair amount of grease (but not gobs of it) to the housing where the o-rings on the plate slide, as well as the three guides. After putting the plate into the housing, I used brake cleaner to clean the face of the thrust plate, and set the assembly aside. Similarly to the thrust plate, I lightly greased the entire thrust cap and degreased the face. The hard part would have been mating the housing and the thrust cap with the clutch disc and spring. Fortunately I found it much easier to put a piece of threaded rod through the center of the assembly and use nuts to compress the whole apparatus; this way there was no fighting the spring and thrust cap in order to get the screws in. You cannot compress the spring all the way down using this method because you will eventually run into the spacer that sits in the center of the spring on top of the bearings. Once the holes are aligned it is easy to Loctite each screw and put it in. I used Loctite 271- the PDF from Evans says to use 272, but I couldn't source any locally. At first I mis-read the PDF and almost put 70 ft-lbs on a screw... it is 70 INCH-lbs! It didn't matter anyway, because I didn't have any torque-wrenches that could do 70 in-lbs so I just tightened them by hand with a screwdriver using star-pattern to ensure the thrust-cap is evenly torqued.

After that fiasco was complete, it was easy to drop the fan-side housing into the rest of the clutch (a bit tricky to align the clutch disc with the posts inside, but it can be done) and apply the remaining spacer, spring washer, and lock-nut. I then applied grease to the o-rings and threads on the cap and installed it. Since assembly was complete at this point, I then verified that I could spin the two halves freely. Hooking it up to an air source at ~10psi, I was able to lock the clutch up and verify it was functioning. There is a small hole on the outside of the fan-housing, near the base of the cap that releases air pressure to disengage the clutch. Be sure that it clear of any debris, otherwise the clutch will stay locked. This may be an issue for those who are encountering a stuck-on fan.

As for the studs that I removed when removing the nuts for the fan, I used the same Loctite 271 to lock them in place. For good measure when mounting the fan, I decided I will use some lock-washers in addition to the lock-nuts it already has.

View attachment 636966View attachment 636967View attachment 636968View attachment 636969
boi thank you helps me when I tackle mine .:goodjob::beer::driver:
 

Boi

New member
19
9
3
Location
Saint Charles, IL
could it be your fan blades? 74m35 had his blades come loose?
I don't think so. Before installation I examine each blade for looseness or damage, and after installation I pushed and pulled on them and confirmed that nothing was loose.

It could be one of the three bearings in the clutch. I added grease to one of the two bearings in the fan-housing; the other was inaccessible. Perhaps repacking the one bearing is why the sound diminished, but not repacking the other is why it is still present. I don't have access to a press or spare bearings, so I don't want to go fiddling with those.
 

74M35A2

Well-known member
4,145
330
83
Location
Livonia, MI
Mine seemed tight to begin with. I loosened the blade fasteners, re-tightened them, and my noise went away. If I was you, I would break them all loose, and re-tighten them all. Maybe even pull the blade off and look closely at it and the mounting area on the hub. Each their own, all I can do is explain my experience and resolution to exactly the same noise you are experiencing.
 

Boi

New member
19
9
3
Location
Saint Charles, IL
Mine seemed tight to begin with. I loosened the blade fasteners, re-tightened them, and my noise went away. If I was you, I would break them all loose, and re-tighten them all. Maybe even pull the blade off and look closely at it and the mounting area on the hub. Each their own, all I can do is explain my experience and resolution to exactly the same noise you are experiencing.
I'm not sure I understand what you mean. Are you talking the nuts that hold the fan to the clutch? Or are you talking about hardware that holds the fan blades together?

When mounting the fan to the clutch I made sure the nuts were snugged up. If this is the part you are referring to, I will go out with a larger wrench and put a few extra ft-lbs on it.
From earlier in the thread:
View attachment 636549
 

gijoel

Member
41
11
8
Location
San Bernardino, CA
Had a catastrophic failure with the air clutch. The failure caused the radiator fan impeller to break loose and cut deep into my radiator. Regrettably, I was 100 miles away from any major help. In order to get it to a safe location, I manage to pinch and fold the fins/ribs of the radiator as to stop most of the water leakage. Every 3 to 7 miles, I had to stop and fill the radiator with water, but I manage to get it to a safe location 47 miles away. Upon closer examination of the clutch, it looks like the 8 set screws came loose and eventually failed causing the clutch to come part, thus, the failure. Anyways, I was planning to rebuild, but upon closer inspection, I discovered the center air shaft was bent by .018" from center line. So I’ll be purchasing a new or used. Here are pictures of the failure.
20170510_170724.jpg20170510_171923.jpg20170512_081232.jpg20170512_082658.jpg
 

gijoel

Member
41
11
8
Location
San Bernardino, CA
Not sure what you mean by fan number. I did call kit masters and they could not help with any of the numbers I provided them from the TM's. They sent me a picture of what "they" thought, but it was not the right kit.
 

simp5782

Feo, Fuerte y Formal
Supporting Vendor
12,125
9,384
113
Location
Mason, TN
Okay, I'll look for one. I've all ready order another oem radiator.

Sent from my SM-G900V using Tapatalk
A member on here is actually selling them or was for around 350. They are aftercooled so you would get more power

Sent from my SM-G935P using Tapatalk
 

74M35A2

Well-known member
4,145
330
83
Location
Livonia, MI
$1700? Tell them to FO. I paid $550 at a local place that custom makes a high volume of them for global replacement applications. The entire thing is copper and brand new, they only reused the end tanks. It was an amazing process to see it all happen. They will likely not show a listing for it, but I can PM you my name, maybe they can pull the diagram from mine and just pound out another for you. This was a few years back. I gave them my old one, and they made a new one right there on the spot, and transferred all the mounts, brackets, shroud, and fittings over from old to new in the exact needed locations. Everything lined up and was good to go. Came with warranty and has not leaked a drop. Is pressure tested under water before shipment. Every fin is perfectly straight, and the entire thing is dyed black (a proper shop dyes it, because paint greatly impedes the heat transfer). They would need your old one if my print is not still around. They could probably give you a base price with your generic core measurement and tell them side tanks design.

http://www.detroitradiatorcorp.com/
 

Swamp Donkey

The Engineer
Steel Soldiers Supporter
1,450
120
63
Location
Gray, GA
I see you placed a wanted ad for a new one. That will be your best bet. I wouldn't think about rebuilding that one and here's why. Not only for the bent spindle, but because the tip of the spindle is a sealing surface for the front cap seal. The tip is chromed and any imperfections will cause it to leak and prematurely wear out the cap seal. There really isn't a good way to remove imperfections from the spindle without removing the chrome or reducing the diameter, both of which are bad.

It also appears your cap seals are worn down. This was probably from the excess movement before failure. The cap is not cheap. It's the most expensive individual piece on the clutch.

I wouldn't reuse that fan either. It has most likely been tweaked and will cause vibration. This will ruin your new clutch in short order. I'd be looking for a fan too.
 
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