I installed a brand new Delco A-10 style compressor in my 380sl last April, and it was leaking from the rear seal immediately. So, I returned it, and got another one, which I installed last May.

Even though I hardly used that one, I was shocked to find that it, too, is leaking from the rear seal, just like the other one was. And as far as I know, I didn’t do anything that should have caused both compressors to leak.

Before I go and replace this one, I was wondering if anyone could tell me whether it’s possible that I got 2, brand new, Delco compressors that leaked, or whether I could have done something that caused them to leak.

Thanks very much in advance for the help.

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1981 380SL
Chassis: R107.045

Just be sure the pressures are what they should be - use gauges to monitor the high and low pressures. And don't add too much refrigerant - do so "by the book" and per factory specifications. If you can, monitor the pressures while driving (higher engine RPM's and thus could be higher pressures). Also there should be an electric high pressure cut-off switch. Be sure someone did not by-pass that.

Other than that, they get some guy working on an assembly line and he does not do his job right. They then have a batch of faulty parts! Could be that. (I once returned 3 rebuilt starters in a row before I got one which worked.)

I was using cans and monitoring the pressures with gauges to insure that I didn't overcharge it. If it there were rebuilt compressors, I could understand it. But they were brand new.

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1981 380SL
Chassis: R107.045

...but "old" seals.

By that I mean those compressors were more than likely stored for a very long time in such a fashion that their "pre-oil" (if they ever even had any) drained away from the seals in question leaving them high, dry, and shrunken.

The guys at my local parts place have confirmed that this is becoming a real problem with new and reman R4 and A6 compressors that don't sell like they used to. They suggest to their customers basically flooding new compressors with oil for a few days and leaving them so orientated as to moisten, soften, swell and re-condition the seals.

The usual disclaimers apply to the following redneck fix.

Add a single drop or maybe two of brake fluid to the flood oil to swell and soften those seals.

Hope this helps...

Hmmm. Interesting theory. But, if it's right, shouldn't the PAG oil I added to the compressor have swelled the seals some time after I installed it?

I suppose I could try adding a stop leak, like Red Angel, to the system, but I don't want to take the risk of contaminating it.

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1981 380SL
Chassis: R107.045

...wouldn't you? But that is what I heard right from the horse's mouth - so to speak.

There might be something to it in that those boys do know what sort of quality (or lack there of) they are selling and they do have an interest in avoiding returns and warranty claims so take it for what you will.

PAG oil plus any sort of aftermarket seal conditioner other than something specifically marketed as AC seal conditioner is probably not a good idea on a nice, new build A10.

When I suggested brake fluid I really did mean adding JUST A DROP OR TWO and then draining all of the oil out after a few days of soaking before re-oiling to spec. I went through 3 re-man R4 compressors on my old HT4100 RWD Cadillac in a year before an old-timer suggested that trick.

Hope that this helps.