A/C evaporator or expansion valve leak??

[LeRoux Strydom]

Hi there

I have started removing the a/c evaporator on my car since it appeared to have sprung a leak. My beloved 964 recently showed the classic tell-tale signs of an oil puddle underneath car where the airbox drain pipes exit combined with losing its a/c cooling function.

Now that I have removed the fuel overflow tank and firewall, the expansion valve is clearly visible, as is the oily mess around it!!





This makes me think that there is a distinct possibility that the evaporator may not be leaking itself, but rather the expansion valve or its O-rings. I have recently (about 2 months ago) converted the a/c system from R12 to R134a. Is it possible that the O-rings in the expansion valve have deteriorated and started leaking? The shop that did the conversion did not change anything other than the receiver/drier, the compressor oil and the gas.

I am calling on the collective wisdom here to please help me out here, as I would desparately want to avoid removing and replacing the evaporator if the a/c leak can be cured by just replacing the expansion valve and its O-rings. I have in fact already received all the replacement parts, including evaporator and expansion valve, but will gladly pack the new evap back into its box and put it on the shelf!!

What are the chances that the evaporator itself is really leaking, given the coincidence of the R134a conversion and the obvious leak around the expansion valve?

Le Roux

[bazar01]

If you don't have the right a/c tools for this trade, it will be tough and pure guess work.

Correct way is to use a D-tek/Inficon R134/R12 leak detector for small and hard to reach area leaks and leak detector liquid in spray bottles for big leaks.

If you suspect the expansion valve is leaky, spray some liquid soap base detector on suspect fittings and in oil soaked areas and look for bubbles.
That is if the system still has some refrigerant left to keep it above atmospheric pressure.
If all the freon has leaked out, you need to pressurize the system to leak test it.
Most shops will pressurize it with Nitrogen and small amount of Freon R134A to about 200 psi and leak test it.

Since it is already converted to R134A, you may just want to recharge it and do some bubble test for leaks.
You can also put some dye in the system and check the location of the leaks using a UV light.

Good luck.

[ron in sc]

I've found the forum in the link below helpful when dealing with A/C issues, consider giving them a try.

http://www.autoacforum.com/categories.cfm?catid=2