One day while parked with the engine idling in front of a friends house; the entire front end of the car was enveloped in a big white cloud. Upon inspection we found no water puddles or other evidence of radiator/water pump/hose leaking. The overflow reservoir was down some but not empty. My Volvo mechanic charged me to install a new cap for the reservoir. I don't think that is what caused the cloud. My air conditioning still pushes out some cool air but it is no longer cold. My question: "Is there some sort of relief valve for the air conditioning"? I had the air conditiong system checked for leaks (free) and was told there are no leaks. My R-134 conversion was done about 4 years ago). Thank You

The pressure relief device is located in the "muffler" that is in a pipe under the front of the car (looks a bit like a can). That was most certainly it. You may need a new relief device that screws into the muffler and/or other parts.
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Paul NW Indiana '89 740 Turbo 120,000

Yes there should be a overpressure relief valve on the back of the compressor or in one of the lines.
If it blew, you most likely either have crud clogging the orfice valve, bad fan clutch/ electric fan ,too much refrigerant in the system, or just a 15 year old valve that decided it had enough
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-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel, '86 740 GLE turbo diesel, '82 Mercedes 300SD for sale

Thank You so much. That twice now that I've received GOOD advice from this group. I think maybe I need a new Volvo mechanic..