Yet another M-1078 Fan Clutch thread

[Pointman0853]

This is simply being posted in the hopes that in the future another member may benefit from what I have learned.

Oh, and yes. I did my searches before posting..

We spent time yesterday diagnosing the issue with the fan clutch on my 1994 M-1078.

With the engine stopped, the fan freely rotates.

With engine running and air supply to fan clutch removed, the fan freely rotates.. This tells me the unit is pooched, and needs to be replaced. With the engine idling and alternatively applying and removing air, you can see the fan clutch moving in and out. this one is toast..

Once removed, I will do a postmortem. I have been told these are rebuild able. If so, watch for that.

With ambient temps here in Northwestern Nevada running in the 90's, this needs to be addressed before I venture out on the Blackrock playa later in September.

Pointman

 

[coachgeo]

this post might help someone understand the why's of the workings he finds in disassembly

http://www.steelsoldiers.com/showth...lutch-Repair&p=1735674&viewfull=1#post1735674


Pulled from below rather recent thread. Granted that thread seems to have opposite issue from Pointman's.
http://www.steelsoldiers.com/showthread.php?137263-FMTV-Fan-Clutch-Repair


UPDATE July 1, 2016: Another thread that will assist anyone in the future testing/working/repairing/understanding the fan's.
http://www.steelsoldiers.com/showthread.php?145266-Checking-the-FMTV-fan-system

 

[Pointman0853]

Thanks CoachGeo for the additional links. When doing my 'search' I could not find anything applicable to my particular problem. After removing and cleaning the electro-air valve (easy) we moved on to the actual clutch itself. Thanks to fellow inmate lmtv722 for the deal on a slightly used clutch. I will document the change out as soon as that part arrives. Yesterday's lunch break was spent pulling up the appropriate manual pages showing the removal and installation. I'm looking forward to getting the old part off and disassembling it to see why it failed. This truck had only 11k miles on it when purchased, and the fan only comes on under heavy load/temp conditions.

Pointman

 

[mkcoen]

This truck had only 11k miles on it when purchased, and the fan only comes on under heavy load/temp conditions.

Never trust a military odometer or fuel gauge. They're often changed and rarely right.

 

[DiverDarrell]

Never trust a military odometer or fuel gauge. They're often changed and rarely right.

So what your saying is that my 1994 m1078 doesn't have 457 original miles on it? Lol. Well since the back face is of different colors so I know for fact mine is not original. And the paint wear on the heater guard and foot steps, I'm going to believe it has maybe 800 miles. Haha (dreaming)

 

[Retiredwarhorses]

Thanks CoachGeo for the additional links. When doing my 'search' I could not find anything applicable to my particular problem. After removing and cleaning the electro-air valve (easy) we moved on to the actual clutch itself. Thanks to fellow inmate lmtv722 for the deal on a slightly used clutch. I will document the change out as soon as that part arrives. Yesterday's lunch break was spent pulling up the appropriate manual pages showing the removal and installation. I'm looking forward to getting the old part off and disassembling it to see why it failed. This truck had only 11k miles on it when purchased, and the fan only comes on under heavy load/temp conditions.

Pointman

the fan is only supposed to come on based on eng temp....this fan clutch setup is no different then 939, HMMWV etc...
you have to hit the water temp to activate the solenoid that open and closes to allow or deny Air or fluid pressure to cycle the clutch....my 1078 works as yours does, and temps are just fine and in the acceptable reading.

 

[Pointman0853]

Fan Clutch, Episode #2.

Fan Clutch, Episode #2.

Since last week, I ordered a fan clutch from a fellow member.

Meanwhile, to further my fan clutch education, I paid a visit to a valuable online resource on all things 'Fan Clutch' at KitMasters.com. Their website referred me to a local distributor in Reno, and I now have a rebuild kit ($125.00) on the way. The part number for this is 8000SKL. It provides everything to return the unit to full operating condition.

These clutches are Model Keysor F22, and also listed as Borg-Warner 'Keysor' style F22. They also show up on the Haldex/Bendix site as well. Two models of this clutch were made, the front activated style as on the M-1078, and a rear activated style for use with idler pulley assemblies.

My resource tells me that although no longer made, these clutches are still supported and there is a YouTube video on how to rebuild them here:

https://www.youtube.com/watch?v=0YuUdOfESKA.

Additionally, he tells me that all of the part numbers listed on page 45-1 of the TM match identically the Haldex part numbers he lists on his ordering system.


Finally, when I receive my rebuild kit this week I will document the rebuild process. The plan now is to remove my old unit and install the rebuild kit. Unlike the unit I purchased, I know my old unit engages and disengages fully when air is supplied. It now appears that the friction lining is the culprit.

Pointman

 

[Pointman0853]

Episode #3.

Following are a series of photos from the weekends 'surgery'. The first is the non-op unit on the bench clearly showing its Keysor and Borg-Warner markings..



Here, we have the unit prepped for disassembly using two 3/8" bolts per the video. Following shows the progression to final cleaning and preparation for the rebuild kit.



A photo of a critical locking washer. This 'tabbed' washer prevents the main shaft from turning when the final assembly nut is torqued down. The one on the right came from the donor unit I purchased. Notice the tab is missing from a previous botched repair.



Here are close ups of the main shaft threads, the photo on the right is how they should look. The first photo again, is from the purchased unit and are visibly stripped. This shaft will require replacement.



Finally, these show removal of the main seal from the unit. I got to play with my new dental tools! it is now cleaned and ready for a new friction ring, seals and reassembly.



Remember, this clutch failed to engage. It came off the crank having a burnt smell to it, much like overheated brakes. It will be interesting to measure the difference in the size of the new friction ring when it comes later today.

Pointman

 

[Pointman0853]

Episode #4, Trial and Errors.

After obtaining what I thought was the correct Kit Masters rebuild kit (8000SKL) I discovered they had sent the kit for the rear air, #8500SKL. Based on my clutch needing the friction lining (the really Expensive bit..), I went ahead and reassembled it using the old seals which looked pretty good. The clutch operated per spec when bench tested. Upon installation it would not disengage when air was applied. It had developed an air leak around the main seal. Doh!

Additional research indicates the availability of just a seal kit, Kit Masters PN 8500SK. For those of you with clutches that will not dis-engage when air is applied, here are your parts. Of course, none of my local Kit Master Dealers stock this, so now its another week wait..

I also spoke to Tech Support at Borg Warner this morning while enjoying my morning joe. I learned some interesting things.. The F-22 fan clutch in our trucks has been replaced by the F-26. The only difference is the angle on the faces where the friction ring contacts the disc. Retail on this is around $450. Additionally B-W no longer supports the F-22 with parts. This goes against what my local dealer tells me that all of the PN's in the M-1078 Manual are active and current B-W part numbers.

If I wern't such a stickler for keeping this as stock as possible, I'd just add an electric fan from Hayden. Sadly the 16" model with accessories is up over $260...

At least I'm getting good at disassembling all the plumbing on top of the engine. That, and I also found a rip in one of the intercooler silicone hoses that had been there for a while

Pointman

 

[DTinNC]

I just had the same issue occur to

Episode #4, Trial and Errors.

After obtaining what I thought was the correct Kit Masters rebuild kit (8000SKL) I discovered they had sent the kit for the rear air, #8500SKL. Based on my clutch needing the friction lining (the really Expensive bit..), I went ahead and reassembled it using the old seals which looked pretty good. The clutch operated per spec when bench tested. Upon installation it would not disengage when air was applied. It had developed an air leak around the main seal. Doh!

Additional research indicates the availability of just a seal kit, Kit Masters PN 8500SK. For those of you with clutches that will not dis-engage when air is applied, here are your parts. Of course, none of my local Kit Master Dealers stock this, so now its another week wait..

I also spoke to Tech Support at Borg Warner this morning while enjoying my morning joe. I learned some interesting things.. The F-22 fan clutch in our trucks has been replaced by the F-26. The only difference is the angle on the faces where the friction ring contacts the disc. Retail on this is around $450. Additionally B-W no longer supports the F-22 with parts. This goes against what my local dealer tells me that all of the PN's in the M-1078 Manual are active and current B-W part numbers.

If I wern't such a stickler for keeping this as stock as possible, I'd just add an electric fan from Hayden. Sadly the 16" model with accessories is up over $260...

At least I'm getting good at disassembling all the plumbing on top of the engine. That, and I also found a rip in one of the intercooler silicone hoses that had been there for a while

Pointman

Thank you for posting all this info. I have a quick question regarding the rebuild kits please.

The fan clutch in my M1081 died yesterday am and began to free spin just like yours. The difference from the details here is that I have the first/alternate version clutch with the 6 allen head bolts instead of the studs and nuts. The front air etc is all the same.

Any thoughts if the 8000SKL full kit would work?

Thank you,
Doug