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Changing GM front shaft seals

Chick on Thu November 15, 2007 9:49 PM User is offlineView users profile

Changing GM R4-V5-HR-HD-HT and DA6 compressor front shaft seals

Sometimes you might have a good compressor, but find the front shaft seal leaking. You can opt for a new or reman compressor, or if you have any mechanical ability, or just like fixing your own car, changing the shaft seal may be the better answer.. Below is a step by step procedure along with the Mastercool part numbers for the tools you’ll need. Before starting, you will have to clean the threads on the pulley and shaft so that the tools will screw on properly. If you don’t “grab” enough threads, you can damage them. Some WD40 and a pick to clean the grooves helps..

Remember when changing front shaft seals that you MUST keep the surfaces clean, and it’s recommended you clean the inside of the “nose” before you pull the seal out. A can of aerosol brake parts cleaner is great for removing oil and dirt from the nose after the front hub is removed.. When assembling, use plenty of mineral oil to coat the shaft and the seal. It will make installation much easier.

Some seals can be replaced on the car, with no need to remove the compressor. You will need to check the space you have to work before making that decision, but it always easier to do them on the bench..

Step 1

Some compressor will have a “nut” in the center of the pulley shaft, some newer ones will not. If yours does, it needs to be removed before attempting to pull off the front hub. The compressor shown is from a 95 Chev Caprice and does not have the nut. Now clean the threads in the pulley…
Once the nut is removed, screw the clutch plate removal tool (Big nut screws into the pulley) into the threaded pulley, and then remove it by turning the smaller nut on the tool clockwise. The “key” usually comes off with the clutch hub, be sure you don’t lose it..

Step 2
Now that the hub is off, you can see inside the nose, and if you have a leaker, it will be pretty dirty. Now is the time to clean it up. Once you clean it well, you can look in and you’ll see the snap ring securing the front seal in place. “THERE IS NO NEED TO REMOVE THE PULLEY” to change the seal, but if you want to, (to clean it up, repack bearing etc) just remove the snap ring that holds in in place, and the pulley slides off.. Sometimes a rubber mallet and piece of 2X4 can be used to persuade it to slide off more easily

Step 3
Once everything is clean, use the internal snap ring pliers and pull out the snap ring holding the seal in place. Sometimes an awl can be used, but will damage the old snap ring. So plan on replacing it..

Step 4
Use the seal removal tool and bottom it out on the indentation on the seal, twist the tool til it grabs the seal, and with a twisting motion turn, and pull outwards until the seal comes out.

Step 5
Next, using a pick, grab the O ring in the groove around the seal (where it was) and pull that out. Use a new o ring when you install the seal The pic shown of the seal is JUST the seal, but the guys at can get the whole kit for you. Seal, snap ring and O ring in one seal kit. Just e-mail them at for prices, and give them the seal number shown in the picture..

Step 6
Use mineral oil and lube the new O ring and push it into it’s groove evenly around the sides. Once it’s in, lube the seal well too. Place the shaft seal protector over the shaft to prevent damage from the threads or keyway. A nick in the seal can ruin it.. Oil up the shaft seal protector also. Slip the seal onto the protector and use the seal removal tool to push it down the shaft.. My experience has been that the master cool shaft seal protector is just a bit to long and could cause the protector to get caught in the tool, so take the tool apart and use just the outer part. Twist it in and down so you don’t risk turning the seal outwards. Once down close to where it belongs, take the shaft protector off and finish pushing it into place (seating it)
Step 7
Now that the seal is in place, you need to install the snap ring. Make sure it seats in it’s groove correctly (beveled edge out) Check it twice.. You hear of guys changing seals and them blowing out. Usually due to improper installation of the snap ring Once it’s in, replace the pulley (if removed) and then locate the key in the shaft about half way into it’s slot. Use the clutch plate installer tools to push the plate on, be sure the key is properly lined up. Press the plate on until you have a gap of about .02 If you don’t have a feeler gauge, you can use a business card. It should fit snugly all around the air gap.

Step 8
Put the compressor back on the car (if it was removed) and pull a deep vacuum and charge the sticker amount back into the system. Retrofitted cars you can follow the vac/charge procedures listed on the FAQ and tips page of this forum.

That about does it. You’ve changed the shaft seal, and hopefully saved a few bucks on a reman or new compressor. Some compressors, if noisy, or oil is contaminated, may indicate a need to replace the compressor. The double lipped shaft seal only fixes the leak common on these GM compressors. So check your compressor out before wasting time and money on a repair, when a replacement is called for.. Good luck...

Tools needed to change the front seal:

Mastercool part numbers
Clutch removal tool #91212
Clutch installer tool 91260 - nut & bearing for tool #90458
Shaft seal protector #90484
Snap ring pliers

Email: Chick


Freedoms just another word for nothing left to lose

Edited: Fri November 16, 2007 at 10:15 AM by Automotive Air Conditioning Information Moderator

Chick on Fri November 16, 2007 6:37 PM User is offlineView users profile

Mastercool Snap ring pliers (Internal) #90383
Seal removal/installer tool #90486

For "R4 and A6" compressors, the "clutch removal tool" is different due to the threads in the pulley, and also a "larger tip" on the shaft for the installer clutch tool. If you have an R4 or A6, contact the guys at for the proper tool, as I am not sure of the part number at this time......Hope this helps.....


"the only thing I do different- is that I always bend the clutch key a tad- and insert in halfway down in the clutch- not the shaft- then there is little or no chance of dropping it out- and there is still room for the insertion tool. The key sticks out of the clutch driver about a 1/4 inch- then I rotate it until it starts onto the shaft, then I insert my clutch installer tool- I did my first one as you described and soon learned to do my last 3500 or so as I described-- you only press a key through the new shaft seal once until you discover a better way. H-6 and R-4 clutch keys are pre-bent from factory installation-- the v-5 keys are longer and not pre-bent- and are prone to slip out easier- these are the ones I bend a little-- or you can always use an H-6 key in a V-5 application. Also the pulleys by design are press fit onto the front head-- but some times will slip off- I always use a pulley puller on it anyway......good job on documenting the procedure---- I have often contended the only thing wrong with most compressors is the leaky shaft seal- no need to replace the entire compressor".............
Below are a couple pics showing what GM tech means about putting the key into the clutch plate, rather than the shaft. A good idea...

Email: Chick


Freedoms just another word for nothing left to lose

Edited: Mon November 19, 2007 at 5:13 PM by Chick

TRB on Wed May 28, 2008 6:07 PM User is offlineView users profile

Little information from our remanufacture. All their A6 compressors come with the double lip seal. Any play in the compressor shaft will damage the seals and cause leaks. They said you may get away if a small amount of play with a ceramic carbon seal. We just pulled the hubs off both our vendors remanufactured and ALMA new A6.

As you can see in these images the one on the left has a ceramic seal and the one on the right a double lip seal.

I have also confirmed that our you will need two different double lip seals depending on the compressor shaft.

Vendor quotes,
MT2230 – MC-1148 measured the top of the can the ID is 18.25mm
MT2105 – MC-556DN measured the top of the can the ID is 15mm If a shaft is 14-15mm then you would use this seal. Anything larger you would use the MC-1148.

You cannot use the SK-771N (MC-1148) on all shafts. It is too big and it will not seal.

Mickey said that he measures the ID on the inside where the Teflon is.

MC-1148 – If the seal is OE it will have the GM number 6560844 stamped on the top of the can. This seal is mostly used for the late model HT/HU compressors.

MT2105 Standard Shaft "Top of can 15mm"

MT2230 Large Shaft "Top of can 18.25mm"


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Edited: Fri October 30, 2015 at 11:00 AM by TRB

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