Well, I've more-or-less completed putting the air conditioner back together on my 124 wagon. The compressor seized when the shaft seal leaked out all the oil. Oops.

This is certainly the least cooperative auto repair I have ever performed. It went about as well as Larry's recent engine rebuild. (Though I did avoid being sent to Europe in the middle of the project...)

Things got right off to a bad start. My goal for the first evening was to remove the old compressor and manifold assembly. The manifold is attached to the compressor via a single 6mm hex head bolt. It was stuck solid. Absolutely would not budge. Since I couldn't seperate the two parts I decided to remove them as an assembly. Getting the manifold hoses out of the car without any freedom of movement - they're still bolted to the compressor - required pulling both the radiator and condensor. Lot's more work than I bargained for. I did feel better when I drilled the bolt out. Take that!

Since I didn't want to risk destroying an expensive new a/c compressor, I purchased a used one at a local MB boneyard. A little degreaser and a pack of shims from the local a/c place and I had it cleaned up and the clutch gap set just right.

Things didn't go much more smoothly putting it back together. Had a massive leak when I went to vacuum it out. Big leak at the expansion valve. Couldn't fix it. Turns out I was sold an incorrectly sized o-ring. Of course, it took me a week to figure this out...

Got that fixed and it was much better - but not perfect. Still seemed to be leaking in the vicinity of the manifold-to-compressor junction. Messed around with that joint a few times but couldn't get the problem fixed. In fact, the problem got worse! Couldn't pull a vacuum below 20"; and you could hear the leak when refrigerant was added.

Turns out the problem wasn't at the manifold hose. There is a casting bolted to the compressor to which the manifold attaches. The compressor itself has two inlet and two outlet ports, both of which face straight up from the top of the unit. This casting reduces this down to a single inlet and outlet port and also makes a 90-degree turn for attaching the manifold hoses. The junction is sealed by four o-rings. When I pulled the casting off, one of the o-rings had actually broken! Replaced all four and voila! A tight system that pulls down to 30" vacuum and doesn't decay at all in an hour.

Things I learned: You can pull the expansion valve out of a 124 in five minutes. It looks completely inaccessable, but with practice becomes second nature.

You can pull the compressor out of a 124 in 15 minutes flat using only hand tools. It's almost as fast to put back in. The fast route is out the top.

If you only want to purchase four o-rings, stores will give them to you. They're too cheap to charge for. I had this happen multiple times.

The best way to find really big leaks is using a spray bottle with a soap and water solution. The leak will blow bubbles for you.

Always use an o-ring lubricant. Refrigerant oil is a start, but the hot ticket is this stuff call "nylog." It's a clear, thick, slimy, nasty liquid which reminds me of having a cold... Give each o-ring a good coating before installation. As a lube it prevents the o-ring from being pinched during installation. As a nasty viscous liquid it actually seals small imperfections and prevents leaks. Really cool stuff.

The internet board at www.aircondition.com is a great resource. (Currently off the air, unfortunately.)

Anyways, I've got the system back together and working well. Despite purchasing a small air compressor (for flushing the system), a vacuum pump (too inconvenient to rent with all the problems), and a case of alternative refrigerant (three-fourths of which I still have) I got out of the deal for $750. Not bad compared to some of the prices I've seen mentioned here. And next time (which I sincerely hope never comes...) I'll be able to do it faster and cheaper. Ugh.

- Jim

FYI, the website http://www.aircondition.com/ is back up and running.

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ASE Master Mechanic
asemastermechanic@juno.com

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

https://www.boldegoist.com/

Do you remember how you got the expansion valve out in 5 minutes?

What size are the o-rings?

-Jim

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1995 S350D, Green with black leather interior.
Bought January 2008 w/ 233,xxx miles.
I did 22,000 miles during the first year of ownership.