Testing for leaks

[robmaxfli]

hi All,

1992 Buick Park Avenue - I'm trying to revive my Grandfather's car that has been sitting for 10 years since he passed. I know for a fact that his AC worked before it was parked. It is still an R-12 car and I have several cans of R-12 left. The Freon leaked out over time because compressor won't engage now. I saw some oily looking fittings at the Accumulator so I opened those up and replaced the O-rings. Some dye and oil burped out of the first connection that I opened.
After tightening I put a vacuum on it and it would show 29.X worth of Hg but when I turned off the pump it would be at 0 Hg in about 10 minutes.
I saw a little dye out of the Low pressure valve and a little on the body of the compressor. I am still not real convinced where the leak is.

I suppose I could add more dye and partially charge with some R-12 but I hate to leak test with the precious R-12. Would it be a bad thing to add R134 and leak test with it? (since its cheaper)

thanks Rob

[Dougflas]

You can add R134 and use it to leak check. The problem is that you should be recovering the r134 after you leak check and "Joe Homeowner" usually does not have recovery equipment.

[GM Tech]

How's the airflow out the vents? That era C cars were prone to evaporator leaks- where the refrigerant oil would leach out of the air inlet face of evaporator and collect dust and dirt that passed through it- virtually plugging up all air flow- It should blow your hair off your forehead- but I have seen some that you could not tell the difference from low to high speed blower. You can visually inspect the air inlet face by pulling out the blower motor resistor pack, (manual system) or the blower motor speed module (automatic climate control system) which is under the relay center on top of HVAC box underhood. 3 7mm screws will let it open up and pull out module or resistor- then shine a flashlight down into open hole and inspect the evaporator face- If oily/greasy (as most OEM were) then there is your leak- It (evaporator) may have been changed already- you can tell by noticing if insulation is cut near evaporator pipes.

The HR compressor shaft seal is second most common leak area- look for oily/greasy slinging streaks from front of compressor

[robmaxfli]

Thanks for the reply. Air flow is great - just not cold. I did what you said about removing the blower thingy so I could look into the Evap case. It didn't feel oily but I saw some green dye specs on the fins from the viewpoint that I had. I am going to get another Evaporator and try it out.
That "case" that covers the Evap and heater core is brittle as heck and has already cracked in several places. I think that when I take the screws out and pull it out, it is going to disentigrate. They are still available from the GM supply houses for $85 - now I know why.

[Dougflas]

If the case is not too badly broken, fiberglass repair kit has worked for me in the past.