I had my system recharged with Duracool, which is an R12 replacement we have here in Canada. Works great. About 2 weeks later I notice the compessor is making a slight grinding noise. It is defineatly the compressor as it goes away when I turn off the AC. I was going to take it back to the guy who recharged it to let him look at it. On the same street in a Mercedes garage. It is not an indy, but not a dealer, just Mercedes authorized shop, MB only. I went in there to see what they thought. The service guy listens to it and immediately says it needs a new compressor. So I go down the street to the guy who recharged it, he looks and says it is a loose belt, it's a lot hotter now, compressor is working harder, belt is slipping.

Oh yea, it's an 85 300TDT

I haven't had the time to tighten it yet

A slipping belt won't make a grinding noise. That would be your compressor eating itself to dust. The longer you run it that way, the more crap you'll have to (hopefully be able to) flush out of the system.

Perhaps the wrong quantity of oil was used, or the wrong type for the refridgerant. The oil has to be miscable (able to dissolve) in the refriderant to do its job.

Ok, I guess I better try to tighten the belt soon to see if that fixes it! Duracool is supposed to be a direct replacement for R12, compatable with the old oil. I describe the noise as "slight grinding" because it sounds sort of like that, but not exactally. I do see the belt flopping at idle, so the belt is a bit loose. What does a slipping belt sound like??

I had a belt slipping on my 84' 300TD and it sounded exactly like an intermittent grinding noise. When I took the belt off I found the issue, about 10% of the belt was "chunked" out randomly. I replaced the belt and all is quiet.

i'm not sure but i'm guessing, re-tightening or replacing the belt will work for a while but wait about 2 to 3 weeks after setting the belt to proper tension and you'll be surprised to hear that "slight grinding" sound at idle again and you'll see that the belt is loose and flopping once again.

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'85 300D Turbo - CA Version

As your system loses refridgerant, it also loses the lubrication oil. Once you lose and recharge a few times (without adding more oil) you eventually run out of lubricating oil.

Then you eat a compressor.

Talk to us in about 3 weeks.

(How's that double platinum Amex card?)

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84 300DT Puke Yellow. Totalled after 438,000
84 300DT Orient Red. 169,000 (actual mileage may vary)
2002 Explorer EB (wife's)