67 A/C Compressor Oil
My 67 was converted to R134 about 20 years ago. Works just fine, but due to a slow leak, have to evacuate and recharge about every 2 or 3 years. My A/C mechanic has suggested a change in compressor oil (which has never been done in 44 years I've owned this car). Is this something that can/needs to be done, or just mechanic blowing smoke?
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1967 Coupe 427-390 w/air -
Re: 67 A/C Compressor Oil
Losing refrigerant can also mean losing some oil, so you may be a bit low on oil in the system. The good news is that the A6 compressor has its own oil reservoir and oil pump, so it gets the oil it needs first.
Original R12 oil was Mineral Oil with 525 SUS viscosity..........which is not compatible with R134a refrigerant. But if the mineral oil is what is in your system, you should probably just add it back versus change to the R134a oil.
Ester oil is compatible with both refrigerants..........but R134a is supposed to really use PAG oil......and not Ester oil. But many of us use Ester oil with no issues for either refrigerant.
Changing oil or even adding oil can get complicated, since if you change oil you need to completely empty the system and compressor, and also change out at least the receiver drier. Then measure the correct oil (and refrigerant) charge back in. Changing to the other oils (Ester or PAG) requires this........with even a better cleaning of the system to completely remove all the old oil.
I guess I would just tell you to stay with what you have and add 1-2 ounces of that same oil back to cover any that has been lost. That should be mineral oil. If you can't figure out the oil that is in the system, then maybe best to add back a small amount of Ester oil. Dom Tallarita has an Ester oil that he really likes..........so you could get the name of it from him. I may have name in my files, but Dom would know best.
Larry -
Re: 67 A/C Compressor Oil
https://www.forums.ncrs.org/asset.ph...5&d=1600376702
Larry,
Some how something changed and I hope the pic comes out.
I remember a oil charge that was sold, that might work and keep the pressure.
The new lable now says synthetic, but nothing has changed.
DomComment
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Re: 67 A/C Compressor Oil
Jeff:
After 42 years the oil is likely deteriorated somewhat, but I would not change it until something else comes up that requires taking the AC system apart. If you still have pressure on the system, no evacuation is needed. But if system is empty of refrigerant, then evacuate and recharge to the required amount shown in the GM Service Manual (should be 3 lbs and 4 ounces).
Larry
EDIT: The refrigerant volume I listed (3 lb 4 oz) is for R12. For R134a, you typically use about 85 % of that number , or 44 oz. Sorry, I forgot that you had changed to R134a when I posted the refrigerant number.Comment
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Re: 67 A/C Compressor Oil
Larry:
Thank you for your comprehensive explanation of this system. I will quiz my A/C guy about all of this. The A/C is working fine, just needs recharging every so often. I run the compressor all the time even in winter when needing heat. Will probably add a bit of oil, as I'm sure some gets lost during evacuating, before recharging.
Dom:
Thanks for your input regarding the type of oil.
All you guys are the best mechanics around.1967 Coupe 427-390 w/airComment
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Re: 67 A/C Compressor Oil
Jeff,
Check for a leak. I rebuilt the A/C system in my 63 8 years ago and it has not been recharged. It still runs icy cold like the day I rebuilt it. Original parts running R12.
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Re: 67 A/C Compressor Oil
An electronic leak detector is the best for finding small leaks in our car's AC systems. All good AC technicians should have one and know how to use it.
For checking for a seal leak on the compressor, I wrap the compressor in a plastic bag and leave it 24 hours. Then make a small hole in the bag and insert the flex pickup from the leak detector. If the seal leaks, you will find it.
LarryComment
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