Automotive Air Conditioning Information Forum

I have a car that I put a vintage air system in recently. It took me about 3 months to finally get the system charged because I was working on other parts of the car, as this is a restoration and modification to this car. So, I finally went to get it filled up and within a week the freon leaked out....I took it back to the guy who did the AC and he did a vacuum check and it held the proper vacuum for over 30 minutes. He also put dye in it. I took it home and used a UV light but didn't see an obvious leak. However in a couple of days it did leak down. I then put in some freon on my own with a bottle that had a gauge and I noticed that the Schrader valve seemed to drip leak a little when I unhooked the fill line to the bottle...my question is, if it held vacuum like it was supposed to, and I cannot find any obvious leaks, is it likely the Schrader valve that is leaking? Would the vacuum test work but not detect a leaking Shrader valve? Any suggestions as to how to find a hard to find leak?

You've got GOOD caps on the service valves, correct? Virtually all schraeder valves leak some.

Cusser wrote:You've got GOOD caps on the service valves, correct? Virtually all schraeder valves leak some.

Cusser, I have what the Vintage Air folks sent me. And they are good and "hand tight". Is there a "leak detector" that works? I was thinking my first step would be to but in new schrader valves....I can get the Mastercool replacement tool for about $40.00 Anything you or someone else recommends to check, i will do that.

Sometimes, a system will hold a vacuum but leak under pressure. And just because everything is "new" ("Never Ever Worked") doesn't mean a system will be leak free.

If it's empty of refrigerant now, add a few ounces of R-134a to raise the pressure and go over every connection with a sniffer. In addition, check the air vents with the sniffer for traces of refrigerant.

If that testing detects nothing, put a shower cap tightly around the front of the compressor and clutch (after removing the drive belt) and let it sit for an hour or so. Then, insert the sniffer's test probe under the edge of the shower cap and see whether the sniffer reacts. If so, you probably have a leaky compressor shaft seal.

If the sniffer doesn't react at the compressor or anyplace else, I'd go back and replace every o-ring at every connection point, coating each new o-ring (use the green ones) with Nylog blue.

Lastly, you could have--inadvertently--installed an incorrect-sized o-ring someplace, resulting in a very slow leak. Replacing them all a second time will probably fix that.

JohnHere,
Thanks much for the comprehensive advice. I have already replace all most O-rings, but I will replace all others. What type of "sniffer" can, I as an armature, get myself to do this type of checks....or if too expensive, I would take it to a "professional".

Not cheap.

https://www.ackits.com/leak-detector-au ... rch=mt1380

you can also find Tek-mates on Flea bay for a lot less and they are used. Figure to replace the sensor which are about $45. I use a Tek-mate on MVAC and they are fantastic for finding leaks.