I dealt with this today, it didn't take as long as I thought it would but I followed sixto's advice and drained off the petcock port, which because of the design, was very easy to accomplish. It also let me consider the quality of my existing coolant, which appears to be a combination of mostly MB but with some green thrown in...yuck.

At any rate the AC compressor is replaced, the circ pump has been replaced, the CCU error codes erased and I think we can close the book on the AC problems. It works amazingly well and to be honest I was surprised that it didn't have an evap housing problem given the propensity for W140's to have evap problems...expensive evap problems!

The circ pump assembly was a pain to reinstall, I opted to replace the whole assembly rather than just the pump, I acquired a used one from a newer W140 that seemed in good working order. But with five hoses to attach in tight quarters it was a little bit of a fight.

At any rate, it's done and all is well...except for the coolant, which since it appears to be tainted, will have to be flushed and refilled. I found that the only place to buy the Zerex G-05 in full strength (not 50/50) is at Napa for $12.29 / gallon, Autozone here doesn't carry it any more. Fortunately they have plenty.

Steve A

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Steve A
92 W140 OM603
97 VW Jetta TDI
90 Passat variant TDI 6 speed MT
94 Chevy K1500 6.5TD
05 E320 CDI
+ others