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1996 Volvo 850 air conditioner won't hold freon

I have a 1996 Volvo850GL. Air conditioner was not working and so I my mechanic recently had replaced the evaporator core which had shown up on the test as leaking. After this was fixed and the system was recharged with freon, it only remained cold for about 4 days (during which time I just drove locally, and outside air temps were in the high 80’s low 90’s).

Took it back to mechanic, and they detected leakage at schroeder valve (sp?) and sealed that. Air conditioner ran GREAT for about 3 days, and then all the freon was gone. This time I drove round trip to NJ (400 miles) and on my way back from NJ it finally lost all of the freon.

Assuming it was a tiny leak somewhere, the mechanic put in “Stop Leak” to fill in tiny gaps etc. He recharged with freon, and it ran better than ever – for only 3 days. Once again I travelled again to NJ and on the way back, it finally lost all of the freon (leaked out somewhere?)

My mechanic is stumped on what the problem could be, since when he uses the dye or uses the “geiger counter type device” to test for leaks, he finds nothing. He is wondering if something is only leaking at high pressure – in other words after running the car at high speeds on the highway, in very hot weather (temps were in high 90’s last time it all leaked out). My understanding is that pressure increases the more the air conditioner is run and perhaps something only leaks and “gives way” at this higher pressure?

Is this possible? ANY ideas or suggestions will be very much appreciated!!

If the refrigerant is being lost that quickly, it has to be a sizable leak. And the refrigerant sniffer should find it. These are designed to detect a leak as small as a half ounce per year.

If he believes it only leaks on the high side while the AC is functioning, then he should run the engine with the AC on, and then use the sniffer on all the high side conections.


You have just discovered an amazing fact…Every ounce of “Freon” ever installed into an automotive air conditioner leaks out into the atmosphere sooner or later… Very few 15 year old cars can be expected to hold their Freon for very long…But if you spend enough money to install central air conditioning in your home, MAYBE they can get it to work for more than 4 days…

Is this a real A/C shop or is it your local mechanic.