Automotive Air Conditioning Information Forum

3) O-ring lubrication:

Obviously necessary. I’d prefer not to have to get more double end capped PAG oil just for o-ring lube since the compressor was shipped with the correct system amount.

I’ve read about Nylog Blue and Red and it is appealing due to its high viscosity and thus ability to seal microscopic surface irregularities. I found this post from John Pastorello, Refrigeration Technologies, the company that makes Nylog:

“You can use Nylog Blue with any refrigerant or system oil. We make two versions of Nylog, one with Mineral oil, (the Red) and the other with POE, (the Blue). Nylog Blue can be used universally. The only reason we still offer and produce the Nylog Red is because too many technicians have never educated themselves that oils can be mixed. Just remember that you can use POE with any refrigerant/oil, but you cannot use 100% Mineral or AB to run an HFC system. About 90% POE is needed in an HFC system to carry residual MO or AB. Hope this helps... Thanks, John Pastorello, Refrigeration Technologies.”

However, I’m concerned that Nylog Blue, because of the POE base will be very hygroscopic, and form acids which may eventually corrode the fitting surface in contact with the o-ring and destroy the seal.

Here is the paper that has me worried:

https://www.qwik.com/wp-content/uploads ... atment.pdf

Don't Treat Today's Refrigeration Systems
with Yesterday's Techniques
By Robert Scaringe, P.E., PhD, President of Mainstream Engineering

“...An understanding of POE oil basics helps explain why the presence of water in the system exacerbates the problem. POE oil is made from organic acid in an esterification reaction. When exposed to water the POE lubricant hydrolytically decomposes back into an acid. The amount of acid generated from POE hydrolysis is dependent on the amount of water available. More water causes more acid to form. Unfortunately, POE, PVE and PAG oils are very hygroscopic with saturation values of 2,500, 6,500 and 10,000 ppm water respectively, compared to only 25 ppm for mineral oil. (That is 100-times to 400-times the water!) While PVE and PAG are different than POE and not subject to hydrolysis, they are still prone to a similar oxidative degradation which also forms sludge...”

As a result I think a different lube is in order.

Parker sells two lubricants, one is barium base petroleum grease (-20°F to 180°F – too close for comfort), the other is silicone based (-65°F to 400°F).

https://ph.parker.com/us/en/product-lis ... per-o-lube

While this is probably the best possible product, there are other silicone greases available for 1/10 the price, (i.e., plumber’s silicone grease at big box stores).

All comments on lubes welcomed.

4) Hard line flushing:

I have all hard lines removed and disconnected from each other and assume that short segments will help with the most effective cleaning. I’ve read a lot about line flushing and at this point think I’m better off having that done for me. Too many variables and I suspect the right equipment and solvents will cost more for DIY and I’ll still not be sure I’ve done a good enough job.

On the other hand, refrigerant flushing (which I would definitely not attempt myself) using R-134a, won’t dissolve leftover mineral oil currently in the lines, which also may have debris that needs to be cleaned out. There is also PAO 68 in the lines from the previous conversion to R134a. PAO, (Polyalphaolefin – actually a synthetic mineral oil) is not hygroscopic, compatible with R143a and R12 and mineral oil. My previous mechanic agreed it was probably the best choice for the conversion at the time, since the compressor was not removed for draining. All of this probably explains the early failure after changing the condenser to a parallel flow type.

I know this sounds unorthodox, but could a detergent (surfactant such as Dawn dishwashing liquid + water) under pressure be used as a pre-flush before traditional flushing solvents to save on solvents (money+environmental hazard)?

90efAACIF wrote: ↑Tue May 09, 2023 11:59 am However, I’m concerned that Nylog Blue, because of the POE base will be very hygroscopic, and form acids which may eventually corrode the fitting surface in contact with the o-ring and destroy the seal.

I think your concerns are unfounded. Nylog Blue has been used for many years in MVAC, is the de facto standard, and has never caused any problems that I'm aware of.

90efAACIF wrote: ↑Tue May 09, 2023 11:59 am As a result I think a different lube is in order.
Parker sells two lubricants, one is barium base petroleum grease (-20°F to 180°F – too close for comfort), the other is silicone based (-65°F to 400°F).
(link)
While this is probably the best possible product, there are other silicone greases available for 1/10 the price, (i.e., plumber’s silicone grease at big box stores).
All comments on lubes welcomed.

Generally, I think you're becoming too involved with minutiae. While you're certainly free to use any lubricant you choose, many professional MVAC techs rely on Nylog Blue for o-rings, fittings, and threads. I do as well, and I've never had a problem. Some techs just use plain PAG oil for those purposes. I can't say how other lubricants would work because I've never tried them and don't want to experiment with unknowns. I would stay away from any petroleum-based lubricants, though.

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