96 850 Replacing A/C compressor, questions

Post by **JimBee** » 11 Apr 2017, 13:05

I realize that much has been written on 850 A/C systems and I have read most of the discussions. But while I have the used replacement on the bench, I just want to probe for any new insights. I'm not going to charge this one myself; it's going to a shop for that. I ran it by the tech at the shop, to him it looked worth taking a chance on. Heck, for $35.00 it's one of the cleaner one's I've seen at a pnp and the system was fully charged when I removed it (carefully, as needed). The pipe from the compressor to the condense that came out with it also looks newish.

Since the original compressor froze, the question was raised whether it "detonated" inside, which would send fragments into other parts of the system. Looking into the ports of the dead one where the pipes are connected, everything looks clean, so I'm assuming and hoping that didn't happen.

Also, related to that, I wondered whether there was enough oil in the system, but not sure how to tell without actually removing and emptying the dryer, which the last shop guy did not do. He just told me the "machine knows how much to add". The shop I plan to take it to for pump-down and recharging specializes in A/C systems and is well regarded in the area, so hopefully he will know how to gauge that.

As for adjusting the clutch, the tech who owns that shop looked at it said "it looks fine" as is. Some say it should be .017" he said, but on a used compressor, .011 is probably better. Any suggestions on this?

I'm using new Volvo 0-rings.

Suggestion on torques for those connecting screws?

Glad to have any other comments.

Post by **cn90** » 11 Apr 2017, 16:16

How many miles when your AC Compressor seized?

- Most AC Clutch gap should be around 0.3 to 0.6 mm. Adjust the gap while the AC Compressor is out of the car for obvious reasons (it is impossible once installed due to the tight space).

- What you described above is "Black Death"...shrapnels showering the AC lines. When you remove the old compressor, check to see if any bits/pieces of metal coming out, if not, then I guess you can get away without flushing the piping system.

I replaced the AC compressor on my 1998 528i BMW @160K miles, the principles are the same (R134a pressure, vacuum, recharge etc.).
The DIY below will give you a good idea:

DIY: 1998 BMW 528i 160K Replacing AC Compressor
http://www.bimmerfest.com/forums/showth ... p?t=924320

Post by **scot850** » 11 Apr 2017, 16:33

Can't remember the name of the little torpedo shaped filter in the line running along the top of the RH chassis leg. You may wish to swap that out as it should prevent most shrapnel from getting further into the system.

Neil.

Post by **JimBee** » 11 Apr 2017, 18:37

Actually, I do have the dead one out and with the pipes off the back the cavities look spotless. The tech I showed it to also shined a flashlight in them and he couldn't see anything suggesting damage. As much of the inside that we could see through the pipe openings literally looked new. It did freeze up, though, so something internal is damaged. The engine was just at high idle when that happened, and the car wasn't moving, so maybe I caught it before a catastrophic meltdown.

I'd forgotten about the inline filter Neil mentioned; I will look into changing that before I put it all back together. Today I bought new o-rings from Kline Volvo, a St. Paul dealer that's a little more sympathetic to the bank account for about $20.00 for the set of 4.

Their career mechanic looked at the replacement and he thought the clutch gap was about right. The gap measures .030" (.75 mm).

But I noticed some oil on the feeler gauge after sliding it through the gap, which concerns me. The A/C tech I showed it to yesterday thought he noticed oil on the pulley, so I suppose it's coming from the front seal. Can that seal be replaced easily? Maybe I'll pull the old one apart tomorrow to investigate. I'll need to get that fixed before I install it.

Post by **Ozark Lee** » 11 Apr 2017, 18:57

Replacing the front seal is usually a bit tough and many times you need a collar tool to get the new one in place without damaging it. I know that is the case with the Delphi compressors that Chevy used. While you have it on the bench it is easy to pull a shim and get the gap down to the low end of spec.

The compressor locking up usually, but not always, means that it locked up internally but I have had one that the bearing locked up on and internally it was fine. When you pull the orifice tube it will tell you a lot. If it is clean then replace it anyway and go ahead and replace the accumulator and pull a good vacuum on it. If there are fine metal particles on the orifice tube then you likely need to flush the system and the condenser coil really can't be properly flushed due to its design.

If you are having this done have them weigh in the refrigerant after they pull the vacuum.

...Lee

Post by **cn90** » 11 Apr 2017, 19:12

The front seal in any AC compressor is challenging to install properly.
By the time the front seal leaks, there is not much life left in the compressor.
I re-use parts all the time, but AC compressor is one item I always buy new, the price is about $200-$300, so it is not that bad. When you look at the big picture $200-$300 is still better than dealing with Black Death mess and other issues. Not to mention time lost chasing problems.

Remember every time you evacuate, draw vacuum, and recharge with new R134a, the cost of that alone is easily $100.

A new Zexel compressor is about $300.

Post by **JimBee** » 11 Apr 2017, 21:42

Okay, I need to think about this. I've got a lot of updating to do on these wonderful vehicles. I really want to tighten up the suspensions. My other 96 needs work on the a/c too. The stop-gap used compressor is fine IF it works for a few years and doesn't cause any costly problems elsewhere in the system. New Zexels locally run well north or 400. On ebay there are some really cheap ones, probably worth the cost of mailing. Autohausaz has a Valeo for high 200's I think and Nissens offers a low 200's new unit. Autohausaz sell a Uroparts accumulator for ~30.00 and has a 5.00 orifice tube. FCP sells a 38.00 accumulator and a 13.00 orifice tube—together would qualify for free shipping. Decisions. If I could replace the seal in the used unit I have I'd probably go with that. Tomorrow is a new day.
I'm going to open the dead one tomorrow and see what the seal looks like. Lee mentions the "low end of the gap", what specifically is that?

Lee is the low end you have in mind the same as cn90 mentions above, .3 mm? Mine is .75 mm. So I'll need to pull the clutch anyway to remove a shim.
Back to the work bench.

Post by **abscate** » 12 Apr 2017, 03:56

I've got a used one from my parts car in the parts forum....and I think Erik has some use d ones too? If he loses his farm on his bet, he might be more pliable

Post by **erikv11** » 12 Apr 2017, 09:03

AC compressor failures are rare, I wouldn't hesitate to put in a used one.

The spec range for your compressor is 0.3 to 0.6 mm.

Post by **Ozark Lee** » 12 Apr 2017, 16:17

JimBee wrote: ↑11 Apr 2017, 21:42
I'm going to open the dead one tomorrow and see what the seal looks like. Lee mentions the "low end of the gap", what specifically is that?

Lee is the low end you have in mind the same as cn90 mentions above, .3 mm? Mine is .75 mm. So I'll need to pull the clutch anyway to remove a shim.
Back to the work bench.

Since you have it out is should be easy to get the gap down to the 0.3 to 0.4 mm. At 0.75 it would likely work OK but sooner rather than later you would be doing the bread clip fix since it is already beyond the specified range.

...Lee