AC manifold vs compressor vs seals vs my brain pan - PeachParts Mercedes-Benz Forum

JimmyL · #1 06-08-2006, 02:36 AM

I was going to post this question on this thread:
A/c Manifold Hose - Block Configuration ?
but didn't want to hijack. (wish I knew how to "name" a link and shorten).

As you can see in below pics, my old and new compressor sealing situation is quite different (old=left, new=right). Based on descriptions in the above linked thread I'm guessing the two seals I'm showing are the correct ones. Correct??? They sure don't completely fill up the outer diameter of the openings, but we don't seal all the way to the outside, so I'm guessing that's OK.
Are those the right seals, or can you even tell?

Also, both have the same looking electrical spades sticking out for my connector. However, one compressor has an "X" on the left spade, one has an "X" on the right spade. Is the "X" for the positive lead, or does that denote something else?

I'm guessing I can mount the compressor, then before I connect the manifold can't I squirt in the oil via a turkey baster or somesuch? To avoid the well-lubed arm......

I would have still been going had it not been for the seal question.
I remember somebody having trouble getting their exp valve in and all lines connected. Wow mine went in easily. 8-10 minutes, including Nylog application.

I definitely need more larger metric wrenches. I'm waring out my 3/4 amongst others.

tangofox007 · #2 06-08-2006, 08:02 AM

Those look like the correct seal washers. As far as adding the compressor oil goes, you are going to loose most of the oil before before you can bolt the manifold up. I am going to bolt the manifild on first, then add the oil from the suction line that opens up just above the compressor (where the suction hose attaches to the hard pipe with the 1 1/4" nut.) I plan to add a little at a time and turn the compressor by hand as the oil is added.

leathermang · #3 06-08-2006, 08:16 AM

While I think turning the compressor by hand is a great thing to do... All I have seen in the MB AC manual for my car is to be sure and not run the engine above idle for at least four minutes after turning on the engine and AC. I think doing both would be the safe procedure.

Pete Burton · #4 06-08-2006, 09:16 AM

I hate to be a Pollyanna, but those seals don't look right to me. I haven't seen your hose manifold, but mine is flat and my compressor is like your old one with the 2 o-ring seals. If you tighten a flat manifold up against those seals, it looks like the load on the manifold will be taken by the torsional rigidity of the seals. I bet it will seal up, but I doubt that it will last. I could easily be wrong on this, but FWIW it doesn't look right to me.

tangofox007 · #5 06-08-2006, 09:55 AM

Quote:

Originally Posted by Pete Burton

I hate to be a Pollyanna, but those seals don't look right to me. (

What would you propose as an alternative?

Pete Burton · #6 06-08-2006, 11:15 AM

Quote:

Originally Posted by tangofox007

What would you propose as an alternative?

Seals that closely match the counterbore diameter(s), with a cross section about 10% greater than the counterbore depth. Durometer of A70. Neoprene has better compatibility with freon than buna, silicone, viton, EPDM or polyurethane.

The manifold needs to make metal to metal contact with the compressor casting all the way around both counterbores, so as to take most of the compressive load and vibration. Otherwise, the seals will, but not for long.

p.s. Maybe that's what they use in those "stepped port" compressors. Maybe the metal rings around the seals crush somewhat and the manifold is spaced away somewhat. Just looks like a less proper way to do it than the simple, trapped o-ring IMHO.

JimmyL · #7 06-08-2006, 11:23 AM

Quote:

Originally Posted by Pete Burton

I hate to be a Pollyanna, but those seals don't look right to me. I haven't seen your hose manifold, but mine is flat and my compressor is like your old one with the 2 o-ring seals. If you tighten a flat manifold up against those seals, it looks like the load on the manifold will be taken by the torsional rigidity of the seals. I bet it will seal up, but I doubt that it will last. I could easily be wrong on this, but FWIW it doesn't look right to me.

My manifold looks like the one in this pic. There certainly isn't alot of "seal material" around the yellow washer. The green one seems to have alittle more. I'm not sure what else there could be though.
Anyone else ever get a compressor like this, and remember their seal setup?

**edit**
I got this compressor from Fastlane. Is it possible this compressor is not compatable with our manifold setup?

James L · #8 06-08-2006, 12:08 PM

you want about a 1-2mm gap between the manifold block and the compressor. on my 1984 i used the green one on the discharge and a black one on the suction, there was not a yellow (ackits new R4), just a red, green and black. i did the red/black and it was crooked and leaked (you could hear it hissing with the vacuum pump running). reinstalled green w/ black and it was not crooked but straight across and all around. there is a 1-2mm gap and no metal to metal contact, does not leak. used nylog.

the o rings are with the remaufactured compressors and the GM type seals are with the new compressors.

tangofox007 · #9 06-08-2006, 02:57 PM

Quote:

Originally Posted by James L

you want about a 1-2mm gap between the manifold block and the compressor. on my 1984 i used the green one on the discharge and a black one on the suction, there was not a yellow (ackits new R4), just a red, green and black. i did the red/black and it was crooked and leaked (you could hear it hissing with the vacuum pump running). reinstalled green w/ black and it was not crooked but straight across and all around. there is a 1-2mm gap and no metal to metal contact, does not leak. used nylog.

the o rings are with the remaufactured compressors and the GM type seals are with the new compressors.

The yellow and black seals have the same thickness and inside diameter. The yellow seal has a larger outside diameter (33.2mm vs 27.9mm for the black seal.) If the yellow one fits in the compressor recess, it's the one to use. There is no means of centering a smaller diameter seal on the suction port.

JimmyL · #10 06-08-2006, 10:14 PM

Well, got the new compressor installed(not fun, not horrible). Adding oil into the compressor seems impossible. I put only one ounce in and rotated compressor around 10 times. (used sheet of black "grip" stuff that goes in bottom of tool cabinet drawers). Even that one ounce leaked out during install.
Learned a valuable lesson. I disassembled the suction line up top, right next to low side schrader, and I shouldn't have put it back together until after I installed compressor. Then I could have squirted the oil down the line towards the compressor. I removed the schrader valve and squirted the oil down there, but it wasn't that easy to do. Kept oozing out after I finished filling.
So, it is out there having a vac pulled. Been about 30 minutes. I'll give it another half hour at least may a whole hour. (depends on basketball game.

)
I await my next set back........

JimmyL · #11 06-08-2006, 11:37 PM

Pulled a 2 hour vac. Closed guages and turned off vac pump.
Time will literally tell.............

Gary F. · #12 06-09-2006, 10:48 AM

Jimmy, lets us know how things turn out. I replaced my manifold seals a couple of years ago and they leak some, have to add freon occasionally, but I am tired of messing with it.

Diesel Giant · #13 06-09-2006, 11:18 AM

Be very careful poring oil into the suction line. You stand a good chance of hydro locking the compressor pistons and they will instantly shatter. When I add the bg oil to the compressor I put the shipping plate back on the back and bolt the compressor up, the quickly remove the plate and install the hose manifold. Yes some will come out but not all of it.

Most of the oil needs to be added into the dryer about 6 ozs. When you add the first 1/2 lb of refrigerant to the system cycle the compressor about 10 times with the low pressure switch to move some of the oil around. If it just runs continuous at first you may have some troubles.

I also dont like that the parts man gave you a compressor with a different sealing rings. The o ring type is the new style the older style has the large washers and is for a stepped manifold. You may be able to make it work though.

tangofox007 · #14 06-09-2006, 11:33 AM

Quote:

Originally Posted by Diesel Giant

The o ring type is the new style the older style has the large washers and is for a stepped manifold. You may be able to make it work though.

My original compressor from 1982 had o-rings. Seems to me that the compressors with the stepped ports and sealing washers are the "new" style. Do you know of a source for new compressors with o-rings?

Diesel Giant · #15 06-09-2006, 11:36 AM

I get mine from NAPA for under $120 bucks.