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Identifying Oil By Smell

94RX-7 on Sun June 27, 2010 12:17 PM User is offline

Is it possible to identify the type of refrigerant oil in a system by smell? Seems that PAG has a smell quite different from that of mineral oil. Does POE smell similar to PAG? Am I just crazy? Or does it all just smell the same when mixed with refrigerant?

bohica2xo on Sun June 27, 2010 2:37 PM User is offline

If I don't know for sure what it is, I like to identify it by the "smell" of clean bare metal.

B.

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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

94RX-7 on Sun June 27, 2010 3:32 PM User is offline

Yes. I know. Always best to flush. Problem is, the car has a parallel flow condenser and from what I understand from reading the handy-dandy forum here, they cannot be reliably flushed to complete cleanliness. I'd get a new one, but they can't be had for love nor money.

The A/C system in the car has never been serviced...so there's no mix-n-match oil situation going on.

Moreover, from a research/curiosity/knowledge standpoint, it would be nice for both myself and the enthusiast community to know if the factory put in POE instead of mineral oil in certain systems...the manual says mineral but it doesn't smell like mineral, and POE was used with R-12 in other applications of this compressor (TV14C) allegedly because mineral oil failed Toyota's durability tests. It seems reasonable to me that they weren't thoroughly documenting the changes made to the systems in these cars during this time period since they were installing 4 different systems in the cars since they had two different suppliers of parts times two different refrigerants....plus the documentation is then translated from Japanese to English. The charge weight specified in the manual doesn't agree with the sticker under the hood.

I'm going to crawl under the car later this evening and try to read the sticker on the back of the compressor and see if it says ND-6 or ND-7 oil, but it is VERY hard to see anything in there....and it would be nice if I could confirm what the sticker says with my nose...assuming that isn't a totally insane notion.

bohica2xo on Sun June 27, 2010 4:18 PM User is offline

If the system has not had a catastrophic failure, you can get the old oil out of a PF condensor. Progressively hotter solvents, and lots of air will do it. The HECAT equipment will do it.

If you have a recovery machine, and a spare recovery tank you can flush it clean with refrigerant.

There are ways. Not normally used, but when a heat exchanger is unobtanium you can find a way.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

GM Tech on Sun June 27, 2010 5:05 PM User is offline

I always identify oil by putting a few drops in a clear beaker of water-- mineral oil floats, while PAG oil will mix in and not float....since it is hydroclospic.......

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

94RX-7 on Sun June 27, 2010 5:47 PM User is offline

Thank you GM Tech! Brilliant!! Why didn't I think of that? I knew the synthetics are hygroscopic...just didn't think to exploit that characteristic.

Cussboy on Sun June 27, 2010 6:55 PM User is offline

I've used our FTIR at my work laboratory to identify refrigeration oils, takes 5 minutes.

My AMA rebuilt in 2003 had PAG in it and I needed mineral oil for my '88 with R-12, so I drained it and flushed a few times with mineral oil. A co-worker soon after bought an AMA rebuilt for his '90 and it had mineral oil in it (which is what he wanted). Both were Mazdas. So it's worth checking.

94RX-7 on Sun June 27, 2010 7:16 PM User is offline

I put the car up on ramps a few minutes ago and looked at the back of the compressor. It says ND-7 oil...I found one reference online that says this is POE 100. Posted another thread here to see if anyone can confirm.

mk378 on Sun June 27, 2010 11:36 PM User is offline

If it was running R-12 it's not going to be PAG. POE can be distinguished from mineral the same way with a water test. There doesn't seem to be an easy way to tell PAG vs POE. A dealer might be able to get true "ND-7" then you don't have to worry about substituting it.

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