Automotive Air Conditioning Information Forum (Archives)

edahall on Mon May 16, 2011 1:51 PM

Year: 1990
Make: Chevrolet
Model: Suburban
Engine Size: Cummins
Refrigerant Type: R-134
Ambient Temp: 90

Once PAG oil has been exposed to the atmosphere, does it all have to be flushed out and replaced?

The A/C on my Suburban has not been working for several years due to a massive leak in one of the hoses. It was converted to R-134 and most likely had PAG oil. From what I understand, PAG oil is highly hygroscopic so since it has been exposed to the atmosphere, the PAG oil left could be saturated with water. I've also read that putting a vacuum doesn't boil the moisture out of the oil, so it looks like I need to get all the PAG oil out of the system. I used a blow gun to apply pressure to the condenser but not much more than a couple of drops of oil came out. The oil that came out was clear with a greenish tint. How do I get all the oil out of the condenser without removing it which would be a huge job because the radiator also has to come out? I'm going to remove the compressor to get the oil of out of it and replace the dryer. Would there be any oil in the rear A/C that I need to deal with?

Will either ester or mineral oil boil off moisture when subjected to vacuum? If so, I would think it would be a huge advantage to use this type of oil in the circumstance of what I'm having to deal with.

Thanks,
Ed Hall

Edited: Mon May 16, 2011 at 2:31 PM by edahall

TRB on Mon May 16, 2011 3:43 PM

If you have contaminated oil in the system. It's best to remove all of it.

-------------------------

When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

edahall on Mon May 16, 2011 3:57 PM

Quote
Originally posted by: TRB
If you have contaminated oil in the system. It's best to remove all of it.

If there are no particles in the oil but it has been exposed to the atmosphere due to a break in the system, does it still all need to be removed? And if so, how do I get it all out of the condenser without physically removing it out of the vehicle?

Since the oil is clean but may have soaked up water due to the hygroscopic nature of PAG, could I just change out the dryer several times until it all clears up?

Edited: Mon May 16, 2011 at 4:00 PM by edahall

HECAT on Tue May 17, 2011 6:54 AM

The oil is old, it is hydroscopic, and how much is in there? The reason only a little blows out is because of the huge internal surface area and the oils ability to bind to these surfaces. Volume, velocity, and the right cleaning chemical is the key. Please read the attachment in my signature for a further understanding of what is involved in proper flushing.

-------------------------

HECAT: www.hecatinc.com You support the Forum when you consider www.ackits.com for your a/c parts.

FLUSHING TECHNICAL PAPER vs2.pdf 

edahall on Tue May 17, 2011 7:55 AM

It was suppose to have 11 oz of oil in the system. The system was converted to R134A 3 years ago with either PAG oil or Ester. Is there a way to tell the difference between PAG and Ester oil? I would like to put the same type of oil back in. Nothing was written down and PAG oil is what is usually sold during the conversion.

With no heavy particles floating around, can proper flushing be attained with the right chemicals and compressor with a blow blow gun attached?

HECAT on Tue May 17, 2011 9:54 AM

A chemical analysis of an oil sample would possibly be the only way to know which oil is in there. This is where proper flushing can eliminate the many unknowns and get you to a clean and dry restart point.

As far as flushing with a blow gun... My professional opinion (did you read the info attached to my signature?) is that anything is possible; like sucking a swimming pool dry with a drinking straw.

-------------------------

HECAT: www.hecatinc.com You support the Forum when you consider www.ackits.com for your a/c parts.

FLUSHING TECHNICAL PAPER vs2.pdf 

NickD on Tue May 17, 2011 10:03 AM

Easy way to handle the condenser is to replace it with a new parallel flow type with an advantage of it being able to handle the additional heat load of R-134a for better interior cooling. The rest is fairly easy, accumulator also has to be pitched. Compressor is drained and flushed out with new oil.

Where is Chick at with his brake cleaner. I have been using NAPA paint lacquer thinner, because it is lacquer, not that crap they sell are hardware stores labeled lacquer thinner that is anything but lacquer.

LOL, why the bug to repair it this year, we had snow here last week and still using the heater. Been too damned cold to even think about AC, where is Gore at when you need him?

HECAT on Tue May 17, 2011 12:22 PM

Nick, what is the part number for that thinner?

-------------------------

HECAT: www.hecatinc.com You support the Forum when you consider www.ackits.com for your a/c parts.

FLUSHING TECHNICAL PAPER vs2.pdf 

edahall on Tue May 17, 2011 9:47 PM

I got it working this evening and it blows very cold. The previous R-134a did not cool nearly as well. I'm going to run it for a while then drain the oil out again and refill.