R134a conversion

[walt]

Thinking about changing over to R134a in the 82. Plan to replace the York with a Sanden and install a new drier. My question is - what is the best way to flush out the mineral based oil from the system? Thanks.

[fred cook]

Walt,

I did the same converson on my '80 911SC last summer. I replaced the York compressor with a Sanden, new dryer, and replaced the old (leaky) hoses with the new barrier type hose. Replacing the hose is very important as the R134 molecules are much smaller than the R12 molecules. The R134 will actually pass thru the walls of the old hoses. The good news is that if you are willing to invest some elbow grease, replacing the hoses is not very expensive. I took the hoses off one at a time, cut off the old crimps and saved the fittings. My local NAPA store had most of the hose sizes and a local tractor (yes, tractor) dealer had the rest. The NAPA dealer had the new crimps and a hydraulic crimping machine so it was a simple matter of removing each hose, cutting off the old crimps with a Dremel, measuring the inside diameter and length of the old hose and having the NAPA dealer install the end fittings with the new crimps. Since I was buying the hose and crimps from him, the NAPA store owner made up the ends for free. When I was measuring each hose, i added about 6" to allow for easier re-fitting. The total cost of rebuilding the hoses wound up being about $130. By the way, there are several different models of Sanden compressors. They are rated by maximum allowable rpm. The one that I used is rated at 7000 max. rpm.

The bottom line is an A/C system that will keep the car cool even on a 100 degree day, uses less power and is smoother/quieter.

Good Luck!

Fred Cook
'80 911SC coupe

[fred cook]

Sorry, just realized that I did not answer your original question about flushing the old lubricant out of the system. Probably just pulling a good vacuum on the system will get most of it. Replacing the hoses and dryer will get some more. That is what I did on my system and have had no problems yet from contamination.

Fred Cook

[stormcrow]

Walt,

There probably isn't much oil in the system because it eventually ends up back in the compressor. However, should you want to make sure, use nitrogen.

If you are doing a conversion, you should probably replace the expansion valve and filter dryer along with the compressor. Once everything is installed, do a pressure test to check for leaks.

After everything has been tested, evacuate the system and charge.

Steve

"A Porsche does more then just go fast in a straight line"