jenyap

Hello,
I’m getting ready to attempt fixing my ac. Here is the story: The ac lines got burned by an engine fire a couple of years ago and I never got around to getting anything fixed. I just got the rubber that got burned replaced by a hydraulic shop and back on the car. My questions are:
1. I realize the dryer needs to be replaced
2. Expansion valve needs to be replaced. (I have rear air does that indicate that I have another valve somewhere?)
3. I’ve heard it’s best to flush the system, what is the procedure for doing that?
4. Does the compressor need to be flushed or is it supposed to be disconnected from the lines when it’s done?
5. Rubber o-rings will be replaced too.
6. I’m planning to switch to r134 what oil and how much of it should I use?
Thanks in advance! The car is a 1986.5

jenyap

Also wondering what the procedure for evacuating the system is

dprantl

Do a search on the list, all of these things have been discussed before. You need to replace both expansion valves because your system has two. You should flush both evaporators, the hard lines and the condenser. Use mineral spirits and compressed air to do this. Make sure none of the flush medium remains afterwards. Do not try to flush the compressor, it cannot be flushed. Every o-ring in the system should be replaced if you are converting to R134A with the correct HNBR type. Ester oil should always be used for a conversion. Drain the compressor of all the old oil. The compressor should be filled with 300 +/- 20ml of ester oil. The system should be charged with 1030g of R134A.

To evacuate the system, use a proper vacuum pump (2-stage) to pull a vacuum for at least 45 minutes to make sure all the water in the system boils off.

Dan
'91 928GT S/C 475hp/460lb.ft

jenyap

Can the expansion valves be flushed or is the procedure done with the valves removed?

BC

Can you get these vacuum pumps for the garage? Or do you need to go somewhere?

dprantl

No, you need to remove the expansion valve and then flush the evaporator. So you need to do both evaporators separately, the condenser separately and the lines themselves separately.

Dan
'91 928GT S/C 475hp/460lb.ft

dprantl

Yes. I would recommend a two-stage pump that can pull to 25 microns (although 50 microns is probably good enough). Something like this:

https://www.ackits.com/pc/90066/Vacu...ge+Vacuum+Pump

Dan
'91 928GT S/C 475hp/460lb.ft

JHowell37

I would suggest that you refrain from using mineral spirits as it leaves a residue in the system. There are dedicated flushing solutions available at the parts store, usually right next to the refrigerant. They're solvent based but leave no residue. All you need to do is give it extra time on the vacuum pump to make sure all of it has evaporated. The stuff also smells better then mineral spirits.

The valves should be removed for flushing and then replaced with new ones.

Use ester oil.

Brendan, I got a 5CFM Robinair from e-bay for $165. Several people sell them.

dprantl

While this is something I have heard of, I have never had any problems with mineral spirits in any of my cars over the years. What I do is I make sure to blow out all the mineral spirits with compressed air. Also, I've seen some "flush solutions" that cost $$$ and smell and look exactly the same as mineral spirits. YMMV.

Dan
'91 928GT S/C 475hp/460lb.ft

BC

Thanks! I need to evac a system and build a new one.