A/C system holds vacuum, but loses freon?

Unclepennybags · Aug 1, 2006

I put my system under 29.0" h.g. vacuum for 1/2 hour. I removed the vacuum pump and it held vacuum for another half hour. The needle doesn't even budge, which to me should indicate a tight system. When I recharge it, it loses freon and stops working after about 3 days. I don't have a leak checker, and I don't see any refrigerant oil anywhere indicating where the leak might be. What types of conditions cause refrigerant leaks when the system is in use while still allowing it to hold a vacuum when not in operation?

Regards,

Mike

p.s. I originally thought that it might be a shrader valve, but have since replaced one. The system still holds vacuum with either shrader valve disconnected from the manifold gauge set.

huffhuff · Aug 1, 2006

the system under vacuum may be pulling a leaky seal tight but when running the system is no longer under vacuum but under pressure so it can leak. try adding a can of sealer if you haven't.

brimac · Aug 2, 2006

If you don't have leak detector, ...might try checking with leak detecting liquid soap. (From ac supplier) System needs to be pressurized, obviously. Will get a little messy, but it washes off. Also, could be a leak in the evaporator, which is visually unaccessable. Might be worth it .. to have an ac shop use their detection equipment on it, and be done with it.

Chris R · Aug 2, 2006

Have you added any green refridgerant dye to the system? Get a pair of those yellow goggles and the black light and you may be able to see where the leak is.

Could also be possible that your evaporator inside the car is leaking too.

doc j · Aug 2, 2006

My first thought was a schrader valve, second is the compresser seal. That large of a leak should leave some oil, maybe on the evaporator?

A/C system holds vacuum, but loses freon?

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