I think I figured out why my AC compressor would cut out, mostly under accelleration. After researching posts on this site, I went to check the compressor clutch air gap. It was within the spec, 0.50mm, but when I pulled the feeler gauage out it was coated with a thick oil. I am almost sure it is refrigerant oil, it has a bad smell to it similar to following a hog truck.
The power steering leaks very slightly (a pint lasted four years) and besides, the PS pump is back a few inches from the compressor, it doesn't seem likely it could get in there. And PS fluid smells a whole lot different.

The compressor is two years old, a reman. I suppose to change the shaft seal would require a discharge and compressor removal.

One question I have is, could an overcharge have caused this, and if the overcharge was corrected, is it possible the seal may stop leaking?

I cleaned the surfaces by repeatedly spraying brake cleaner in there while intermittenly engaging the clutch. It came pretty clean, but I wonder how long it will remain so.

I would appreciate any feedback from those with AC experience.

Thanks, Brian

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Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 120K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
10 Sprinter 3500 chassis with a Class A Winnebago on it. 56K

I believe that it would require an evacuation....
But do not think it would require removal of the compressor... if one had the correct tools....

Hopefully someone else can speak to the thick oil on your clutch.

I don't know for certain if this is true for an 87 Diesel, but on either of my 92 V8 cars the A/C will cut out if the serpentine belt slips enough. In my case, it was caused by bad belt tensioners. The symptom is that the compressor will cut out after a hard accelleration and will either stay off for a few minutes, or will stay off until I cycle the ignition key.

I would usually hear a brief shreik from the belt as I let off the pedal from a hard accelleration and then begin to notice that the A/C was blowing warm air...

Just a thought...

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92 500SL
92 400E (Sold)
87 300E (Sold)
83 300D Turbo (Sold)
75 300D (Sold)
74 240D (Sold after 20 years)

I just rebuilt my compressor last week and it will require evacuation. Doing it on the car would be difficult with all the snap rings involved. Mine was leaking from the ports so I took it off the car and discovered more oil leakage from the front where the shaft seal is so I decided to replace all the seals. What kind of compressor is it? If its a nippondenso like mine there is a good writeup at www.pelicanparts.com/techarticles/911_Nippondenso_rebuild/911_Nippondenso_rebuild.htm. Took me about 45 minutes to rebuild with a kit from acsource.com. Works like a champ now with no leaks

Oh yeah I forgot to mention that the infamous klima relay will not allow any slippage of the belt or a/c clutch without disengaging the compressor. Hard accelerations usually provide this slippage or change in compressor rpm, triggering the klima to cut-out the compressor. Your compressor may be fine for a while with a cleaned clutch, but how much oil is being lost? Better to seal up everything tight and avoid an oil starved compressor

Thanks for the replies, that was a great article and it's my same compressor. Looks like between the compressor and the dash pods I have a couple weekends of AC work ahead of me. That seal must have started leaking not long after the compressor was installed by a local AC shop for $900.00. I still have my old vacuum pump and gauages and about twenty lbs of R-12, altho it's been a while since I have done AC work, and I have never opened up a compressor. I have a whole box of assorted clutch removal tools I got at a yard sale, maybe one will work on the Nippo.
On second thought maybe I better have it charged at a shop, it's pretty hard to measure the right amount from those 12oz cans.

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Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 120K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
10 Sprinter 3500 chassis with a Class A Winnebago on it. 56K

hey skivvies which oil / viscosity did you use?

__________________
Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 120K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
10 Sprinter 3500 chassis with a Class A Winnebago on it. 56K

I used PAG 46, but this is in an R134A converted system. R12 would require a mineral oil. The oils are specific to the refrigerant being used as mineral oil is not miscible in r134 and vice versa. Mineral oil for R12 use in cars is standard 525 viscosity, which would match your thick oil discovery. If you have the equipment and more importantly the freon, its not too hard to get your system going again. I found the hardest part to be the snapring holding the electromagnet for the clutch, as the tips on my snapring pliers were either too small or too big. After that the seals were a breeze

I would worry about the underlying reason that would cause seals to fail after two years.....such as a rouch sealing surface or shaft movement due to excessive bearing clearances.....I give you 99.99% odds that it will fail within 2 more years...possibly even withing a year.

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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

If the system still has a good refrigerant charge, then it is probably not the compressor seal. If it does not and you do indeed replace the seal, the MB manuals indicate that the seal should be replaced on the bench. I don't think you can fit a puller in place without removing the compressor.

An overcharge causing this seems to be unlikely.

With the clutch clean, I think I'd run it a little and see what happens.

Good luck,

I agree with Larry, with one caveat. Overcharging the system can definately cause oil leakage at the shaft seal. BTDT. In my case I never found out whether it would stop leaking when the charge was corrected because the compressor seized first. But it cooled great right up until the moment it stopped working (on a road trip to west Texas, 400 miles from home. Oops.). I remember thinking the compressor seemed to be making some noise that I did not recall hearing earlier. Thought to myself that I should look into that someday. Someday never arrived...

So, two comments. First, you would be surprised how easily the power steering pump can dirty up and lubricate the compressor clutch. My '87 wagon had a brittle and cracked return hose from the self leveling reservoir to the pump. It didn't leak more than a couple ounces a year, but it was enough to keep that part of the engine bay filthy, especially the compressor. Got fixed when I accidently broke the brittle hose while working on something else. After that, it stayed amazingly clean.

Second. If you're worried about losing oil from the system, have two ounces added. There are gadgets available that shoot the oil in using a little bit of refrigerant, or find a good a/c specialist to do it. Shouldn't cost much, and only a small amount of R-12 is required to propel the oil in.

Finally, the compressor needs to be removed to rebuild it. Pulling the compressor out of this car is a 10 minute job, there are only three steps required. 1) Remove tension on the serpentine belt (1 minute). 2) Unbolt the manifold hose assembly (6mm allen head socket, 1 minute). 3) Remove four bolts holding the compressor to the engine. (12/13mm wrench - I forget which, 5 minutes.) Unplug the electrical connector and maneuver the compressor back, up, and out of the engine compartment. It will come out the top.

Good luck,

- JimY

I Think I will steam clean the egine bay then moniter it carefully. I called the shop today where they installed it 23 months ago. They said it would need another compressor installed ($1,100) since there are no parts available for that compressor! I think I will steer clear of them from now on.

__________________
Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 120K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
10 Sprinter 3500 chassis with a Class A Winnebago on it. 56K

Boneheaddoctor I thought about that too. It was probly a crappy reman and leaked from day one. If I have to fix it, I'll examine the shaft for wear. Back in my younger days I remember when we tore down our low budget hot rods and found a groove worn on the front of the crank we would just put the new seal not quite all the way seated so it would ride on the undamaged part of the crank, maybe I can do that with the compressor seal? Sure worked good on the old 455 Olds.
If the bearings are bad, I'm not sure if I'll be able to tell, and, I probly won't be able to do anything about it anyway. So if they appear sloppy maybe it is time for another compressor?
Thanks for all the help this forum is great.
Brian

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Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 120K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
10 Sprinter 3500 chassis with a Class A Winnebago on it. 56K

If she wasn't such a beautiful car I would've stopped spending money on her by now.....this year alone, fan clutch & fan, injectors, cruise amp, exhaust and turbo flex tubes and she still needs dash pods, turn signal switch, tires and the sunroof won't open. But she looks like a new car and gets great mileage.

__________________
Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 120K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
10 Sprinter 3500 chassis with a Class A Winnebago on it. 56K