zoltan944

Darien,
email me at zoltans4@hotmail.com if you need more help. I have done the run around on many of my porsches with the AC before. But mroe than likely you have a leak

Bill Ball

Typically not much of the oil leaks out with the freon charge. Most of the stays in the compressor, drier (very little: 10cc) and evaporator. So, don't go nuts with the oil charge unless you do a complete flush (not needed unless there is compressor seize-up). Find and fix the leak(s) and have the system vacuumed down and charged. When you had it serviced recently, didn't the guy vacuum it down and check for leaks?

dr bob

I'm convinved that too many AC techs rely on the "vacuumed it for 10 mins, turned the pump off for 5 mins, gauge didn't move much so it must not be leaking..." method. Looking for leaks under vacuum has two basic shortcomings. First is that the vacuum will pull any slip joints tighter, when pressure would push them apart and show up a leak. Second problem is that you see less than 15 PSI difference in pressure, so any leak that still leaks won't be very big compared to 50-300 PSI system pressures while running. Using the gauges to detect leaks is a poor method even if you put a little gas in there, since the gas will change pressure with ambient conditions even with a small leak. So the only valid leak detection methods are the electronic (or propane?) sniffers, or the dye-and-ulraviolet method after the system has been run a while.


My too sense...

Darien

Hi Bill,

We did not vacuum it or look for leaks, it seemed to hold freon for the first couple years. The leak must have grown

Darien

Bob, Will definately perform one of the recommended leak checks. I think the guy uses the "dye" method

Bill Ball

You still likely have a partial charge and a Freon sniffer would work as well. My car held for 2 years before the charge went below the minimum for the low pressure switch, and I still could easily find the leak with my sniffer. Anyway, vacuuming should be for several hours or more depending on the pump used with a check for at least an hour afterwards.

dr bob

Darien--

You really want the system vacuumed/evacuated and dried out before you put new gas in, and after you identify the leaks. I found a great laboratory-quality vacuum pump at an auction yaesr ago, and it sucks the needles off the gauges. I leave it on overnight to be sure all the moisture is boiled out before charging. If you don't evacuate, you have a partial charge of air in there. Air doesn't condense in the condenser, doesn't evaporate in the evaporator. It pigs heat excahnger capacity and fools the expansion valve. It can also cost you up to about 15 degrees of system temp even before the losses of exchanger capacity.


I have an electrocnic sniffer in my collection of things. You are welcome to use it for the costs of shipping. IIRC it was about $8 each way when it went to Phoenix a few years ago. Might be a little more now but you get the idea. PM me with your address/contact info if you are interested. It's handy for finding leaks, as Bill points out. It will find very small leaks, down to the ounces-per-year level. Since you are leaking ounces-per-day, yours should be pretty easy to locate. The sad part is that the sniffer doesn't fix leaks, only identifies them for you. Oh, and plan on getting a new drier since you'll have the system open for any leak repairs. FWIW, on cars as old as ours, it's not a bad idea to just replace all the o-rings and have the hoses rebuilt, even if you plan to stick with R-12. They are all the same age, so the first leaking joint is just the tip of a a big melting iceberg.