A tad long, but there's a lot of good info you may can use if you decide you want to tackle a reseal job on your R4. I had to repair mine, but if yours leaks, doing a reseal job is almost as intensive, but not as invasive as what I needed to do.
Yesterday, I completed, sort of, a 1131198 A/C compressor conversion from a 1131622 compressor. My plans are to use it on my 85 442 temporarily as an experiment of sorts to see if R152 actually works. I didn't take pictures because 1) there's a lot of videos on how to reseal a compressor both shell and shaft seals, since that's a couple of the major leak points of these things. GM decided in their infinite wisdom to use a single lip shaft seal on it, and 2) I was too lazy. This isn't a hard job, but you will need a couple of specialized tools, and it really helps to have a GM CSM handy.
I had the original 622 that came off my 87 442 that puked and choked soon after I bought it. It turns out it blew a piston off its rod and mayhem ensued. Locked it down and instantly fried the clutch to boot.
For those who haven't messed with the R4 compressors much, there are TWO types used on Cutlass. I cannot attest to any other G-body as I don't own or work on them, so I only know the 198 and 622s. Up through mid- model year 1986 they used the 198 on Cutlass. Then the 622. The main difference is the front bearing housing and the internal cylinder shaft, which cannot easily be removed by the regular Joe Mechanic. It's basically part of the assembly. The shaft is about 5/8" shorter on the 622 than on the 198. Why? I don't know. Uses the same seals, but it's called the "short shaft" and the 198 obviously, is known as the "long shaft". The drive clutch is a different part number, yet everything else left is the same. Interestingly the seal area on the 622 and 198 shafts are in the same place. Although, the 198 does have a couple of flat spots on it near the rotating assembly where the 622 does not.
The rotating assembly cannot be easily dismantled. The pistons are press fit onto pins on their connecting rods and apparently once one of them let loose, it's done. And no repair parts were sold separate to fix it anyway.
Getting the rotating assembly off was a bit daunting. With the belt pulley, it's that big ol' monster in front. It's best that the magnet, and pulley, and rotating assembly with rotor bearing comes off TOGETHER. They can be disassembled after removal. You can remove the 6 little perimeter bolts on the pulley beforehand, but then you will need to use a puller to get the magnet loose anyway. Don't damage the ceramic on the magnet, though. It wouldn't take much to pull the magnet part, though.
With the serpentine pulley, it's much easier to remove. In fact, I even have a puller for that style. But the belt pulley needs a small, specialized 3 leg inside puller to work. Problem is, it's a unique little unit and many of the small pullers I was able to get my hands on won't work. All is not lost. I figured since I had new GM pulley, magnet, and rotor assemblies, I could try it with a 6" puller on the back of the pulley. If something got hosed, then I'd just use new parts. Going slow, I was able to bring the entire assembly off the nose with very little effort on the puller's part. My fear was bending the pulley, but that didn't happen.
I put a new bearing in the front head (bolt-on nose) assembly. A little roller bearing. A note about this. There's an oil hole on it that SUPPOSEDLY it's supposed to be in the 12 o'clock position when installed to allow oil to drain into the front shaft bearing. It's marked with a little cast-in "X" on the top to mark where it is. X goes up. However, some Mercedes cars using the same compressor has the X facing down when mounted. Not sure if there's anything to this, but hey, It came out in the 12 o'clock position, so it went back the same way.
There is one definite thing you should know about R4 compressors that sit around on your shelf. R4 pancake compressors take a bit of effort to turn as it is. But after a while, they get really stuck. Not impossible to turn, but there's not much place to grab onto the drive clutch to turn it. You do not want to use the 9/16" nut on the end of the shaft, you will likely twist it off.
And here's why I believe it gets tougher over time. The piston seals appear to be some sort of rubber and or rubber/fiber compound that resemble an oil-less air compressor piston seal ring. But interestingly, when the piston is brought to the bottom of the bore, a portion of the piston seal is brought down BELOW the bore, being exposed. Two pistons are up, and two are down at any given time due to the rotation of the cylinders. If the assembly is left on the shelf with a piston all the way down, the exposed portion of the seal expands slightly over time, making turning of the shaft nearly impossible. This goes for the replacement rotating assemblies as well, if you have any. I used a drive clutch and a webbed (not rubber) strap wrench wrapped around the drive clutch (not much to grab onto, though) and put the shaft key in and was able to turn it around and "break it loose" so to speak. It's a **** if you don't have a good method to hold the cylinder. I have a shell remover/installer tool, and it comes with a "leg" on it to use in a vise to hold the compressor guts. Ultra-handy, but not absolutely needed.
Another important tip in doing this job is that besides the shell o-rings leaking, the shaft seal leaks too because of it being a single lip seal. Which works fine when running. Delco used to sell a double lip seal, which I have a few on hand, so that's what I used. It's infinitely better at stopping leaks, especially if the shaft is stopped. Delco replacement shell o-rings are buna-N, which are great with mineral oil and R-12, but most kits you can buy aftermarket have better materials that are more compatible with R134/R152. So I used those. With those two items addressed, I think it will stand a better chance of not leaking. We shall see.
SO....
Since it was going on the 85, I figured I might as well look the part. I didn't want to buy one of those light duty R4 compressors, and everything rebuilt by the mass rebuilders I don't really trust anyway. I re-used the magnet and honker sized pulley with the 6 bolts. I used a new rotor and drive clutch because the old ones were toasted anyway. Besides, I was converting over to a long shaft anyway, so the replacement part was for the long shaft.
If you can, use NEW drive clutch and rotor if possible if you have to change them. "Rebuilt" clutches means they resurface the clutches and may trim them off too much which reportedly causes cracking over time. Don't know for sure, but there you go. You do you.
There is a special key the factory and GM replacements use for the drive clutch mounting. It's SLIGHTLY bent in the middle, with the bend peak facing away from the shaft during installation. I'm basing this on how I found it when removing.
Additionally, one last tip. Using the drive clutch installation tool, get some feeler gages to set the "gap" between the rotor and drive clutch faces. The spec is 0.020"- 0.040". I set mine to 0.030" nominal clearance measured at 4 different places around the clutch. SNEAK UP on the setting. The clutch installer tool has coarse threads, and moves the clutch in quite a bit rather quickly. So when you get close, go slow. If you get it too close, you'll need to use the puller to move it back out. PITA.