Hydraulic Fan Clutch Replacement...

[85 USMC M998]

My HMMWV hydraulic fan clutch has developed a major leak. Is there a conversion kit to an electric clutch? Or am I better off just replacing the clutch with the same?
Thanks in advance.

 

[Retiredwarhorses]

They can only leak from 2 points...the fitting and the main seal...the seal,can be replaced without clutch removal.
undo the small nut and remove the clutch cup, these can be a real,Pita the get off, but they do come off, then you have to find that size oring...I think I got one at napa.
or off you have to replace just go with another of the same...belted on eBay always has alot of good NOS or takeout...to test it before it goes into the truck, run compressed air into the HUD fitting to see if the clutch engages, this is also how you ge the bolt holes to line up...if it won't budge, whack to back of it with a good dead blow mallet till it will.

 

[85 USMC M998]

TheHummerguy
Thanks! Good to know I don’t have to remove the clutch. I'll double check the fitting, if it's tight on to the main seal. Next thing I have to do is replace the time delay module; have the replacement already.

 

[Retiredwarhorses]

Is it not working?

What I do is take the solenoid valve off the truck, blow it all out real good...I have seen them clogged. Also do the TDM.
another issue is the clutch plates in the fan clutch plates get stuck...hence take it off and whack the crap out of the back side of it and use compressed air to watch it go in and out...if it does....it will work. I have had more then you know NOS out of the box need this treatment to get the plates unseized.
remember, if the clutch is not working it defaults to engaged and the fan spins....as long as HYD pressure is on, it free wheels....still spins but u can actually stop it with your hand....don't try this.

 

[85 USMC M998]

Correct the TDM has stopped working some time ago; I have been just jumpering the unit as I don't drive the HMMWV as much as I would like an it is always mild temps. Thankfully the clutch an solenoid are (were last fall when put away) working. Thanks for the info. I am going to take a look at it this weekend, I hope... I thought I was going to have a chance last weekend but something always comes up and since the HMMWV is not daily transportation it always gets the back burner...

 

[85 USMC M998]

Well finally go to it. Surprisingly enough the hydro clutch cup came right off. The o ring on the shaft/bolt was bad. The main was OK. The seal is torn so I need to start looking for a replacement. But truck is drivable for now. Thanks for the help!

 

[McSpeed]

Well finally go to it. Surprisingly enough the hydro clutch cup came right off. The o ring on the shaft/bolt was bad. The main was OK. The seal is torn so I need to start looking for a replacement. But truck is drivable for now. Thanks for the help!

Did you find an easy quick source for the main rear dust/dirt seal on the cap?

 

[85 USMC M998]

Did you find an easy quick source for the main rear dust/dirt seal on the cap?

I have a box of assorted o rings I bough from Harbor Freight some time ago; found one in there.

 

[AAron69]

My HMMWV hydraulic fan clutch has developed a major leak. Is there a conversion kit to an electric clutch? Or am I better off just replacing the clutch with the same?
Thanks in advance.

I have a really dumb question. To get into my hydraulic fan clutch, do I need to remove the radiator? I can't get my hands near it with the fan shroud in the way. Is there an easy way to get to it?

 

[McSpeed]

I have a really dumb question. To get into my hydraulic fan clutch, do I need to remove the radiator? I can't get my hands near it with the fan shroud in the way. Is there an easy way to get to it?

The second time I did it - I realized it was best accomplished through the passenger side of the radiator fan shroud. Not a lot of fun, but you can get that off, do what you have to do in that limited space and slide it back in.

 

[AAron69]

The second time I did it - I realized it was best accomplished through the passenger side of the radiator fan shroud. Not a lot of fun, but you can get that off, do what you have to do in that limited space and slide it back in.

After I get the fitting off, what bolts am I looking for? Are they all in front of the fan? Or do the belts and pulleys need to come off?

I do appreciate any help

 

[McSpeed]

After I get the fitting off, what bolts am I looking for? Are they all in front of the fan? Or do the belts and pulleys need to come off?

I do appreciate any help

So...it has been a little while since I last did it. You will need to get an air fitting to the clutch to lock it in place. That will allow you to get the nuts out after you align the holes between the inner/outer of the clutch assembly. You'll leave the fan blade in the housing (just set it aside) and snake the clutch out. It is a PITA . Good luck! I should have done a youtube video the last time...I was in just too much of a hurry to replace it.

 

[AAron69]

So...it has been a little while since I last did it. You will need to get an air fitting to the clutch to lock it in place. That will allow you to get the nuts out after you align the holes between the inner/outer of the clutch assembly. You'll leave the fan blade in the housing (just set it aside) and snake the clutch out. It is a PITA . Good luck! I should have done a youtube video the last time...I was in just too much of a hurry to replace it.

Is there any diagrams or photos of what I am dealing with? I think I would have a better time with this if I could visualize the individual parts involved.

The hydraulic line to my fan clutch was not hooked up when I bought the truck. After I hooked it up I found out why. It blew hydraulic fluid EVERYWHERE!.

My fan is Always Engaged. So the motor never really warms up. It sounds like a bearing my be starting to go out or the clutch was starting to make noise from being Engaged all the time.

If anyone has any schematics I would love it.

 

[Andyrv6av8r]

I just replaced mine last weekend without removing the radiator. Mine is a serpentine belt which I loosened but no need to remove. 99 percent of the work was done from the upper passenger side. I find it easier to remove the qd fitting from underneath. I removed the clutch and fan assembled out the top after removing one of the idler pulleys. So the holes in the clutch halves have to be aligned to remove the 4 socket head bolts ( 5/16 allen) If your holes aren't lined up, just loosen the six 8mm bolts on the back of the clutch which allows you to spin it. The allen head bolts are tight but I was able to get my cordless impact through the blades with a hex driver socket (5/16 allen) and spin them out. After removing fan/clutch, replace clutch and make sure the holes are lined up before reinstalling. It goes in much faster than coming out.

 

[85 USMC M998]

The second time I did it - I realized it was best accomplished through the passenger side of the radiator fan shroud. Not a lot of fun, but you can get that off, do what you have to do in that limited space and slide it back in.

I was able to get my arm between the blades and the shroud, I believe I went through the top and side on the driver's side. Thankfully I and not the Hulk but it is a PITA and expect to get some cuts on your forearms from the sharp blades.

 

[gentech]

Is there any diagrams or photos of what I am dealing with? I think I would have a better time with this if I could visualize the individual parts involved.

The hydraulic line to my fan clutch was not hooked up when I bought the truck. After I hooked it up I found out why. It blew hydraulic fluid EVERYWHERE!.

My fan is Always Engaged. So the motor never really warms up. It sounds like a bearing my be starting to go out or the clutch was starting to make noise from being Engaged all the time.

If anyone has any schematics I would love it.

how did you fix the hydraulic fluid leak? did you replace the quick disconnect?

 

[Mogman]

how did you fix the hydraulic fluid leak? did you replace the quick disconnect?

As was stated above it can be ether the quick connect or the o rings in the clutch, if it is the quick connect all you usually have to replace is the female end.

 

[gentech]

As was stated above it can be ether the quick connect or the o rings in the clutch, if it is the quick connect all you usually have to replace is the female end.

Thanks bud, if you don't mind me asking , do I have to remove the radiator or anything g to get to that fittings, looks impossible to reach it.
Really appreciate the Info.

 

[Mogman]

Thanks bud, if you don't mind me asking , do I have to remove the radiator or anything g to get to that fittings, looks impossible to reach it.
Really appreciate the Info.

Well most can get it done without removing the stack, it is a bit difficult and some blood will likely spill, RWH pretty much laid it out in post #2 above.
I have removed,reconnected that line several times, on the V belt trucks you have to remove the line to change belts and there is usually no quick connect.