Speedtoys

From the low side, should you expect it to also vent out oil as well?

dprantl

Yes, and maybe even liquid refrigerant too if you vent too quickly.

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

Speedtoys

Yup..and my continued searching verified this here.

https://rennlist.com/forums/7617215-post14.html

Thanks for the reply Dan.

I was doing AC work away from my service manuals.

Im a bad bad man.

borland

The oils used are compatible with the type of refrigerant so that they flow throughout the system and provide proper lubrication to both the compressor and expansion valve(s) which have moving parts.

The oil is not disolved in the refrigerant as if it were a solvent, but moves with the refrigerant as an emulsion. With no flow, the oil which has a higher density will eventually settle to the bottom of low spots throughout the system. So, if you allow enough time and your lucky, you may be able to purge excess refrigerant without removing any oil.

With R134, you need to monitor the pressures very closely, as there is really no way to sense how much excess was added. With R12, you can at least use the sight glass to look for the absense of bubbles which works well when adding to a low system.

But with the availability of barrier hose, a system shouldn't have leaks, so topping off is no longer needed. Any old R12 systems should be upgrade to barrier hose. To avoid overfilling, its best is to drain all refrigerant, then refill with known quantity.

borland

Rethinking this. If you let the system return to room temperature, you could boil off any amount of refrigerant from the low or high side fittings without removing any oil.

Speedtoys

Ya. That works too. Just trying to see what's up with my system today.