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Small AC leak

I have a 1990 300ZX that I bought new back in 1989. It has 180,000 miles and is in pristine condition inside and out (OK so I’m anal about my cars…so what!). It hasn’t been my daily driver for a number of years and has developed a small freon leak (1lb in 2 years) in the compressor and discharge hose. I had it retrofitted from R12 to R134a. To repair the compressor and discharge hose leaks will cost over $1,000.
Since I put so little miles on it these days (maybe 400 or 500 miles in a year), I figured I would just go to AutoZone or Pep Boys and by a charge kit and do it myself as needed since there is no longer any R12 to recover.
2 questions:

  1. Do the recharge freon cans include PAG oil since I would assume some of the lubricant will escape with the freon?
  2. Has anyone tried any of the stop leak products to advise whether it really works or just makes things worse…a whole lot worse.

[sigh] Just get it fixed or live without air conditioning. You can’t recharge it every day, and what you are proposing is both a hack solution and a waste of money.

Yes you can get the recharge cans with PAG oil and stop leak and leak detector. The stop leak can work on very small leaks only, yours might qualify.

Before you use a refrigerant with PAG oil, make sure your system uses PAG oil in the first place. I think most R12 systems used an ester based oil instead. I don’t know if the two can be mixed successfully or not. Also, while some oil will escape with the refrigerant, it won’t be much and you do not want to add too much back into the system.

Just like your engine, the compressor can tolerate some loss of oil better than it can tolerate too much oil. Some cans come with 1/2 oz of oil, some come with 2 oz. If you get one with oil, I’d stick to the lower amount.

I have actually seen the stop leak work. I was having a small leak from the low side schrader valve. I thought I had gotten it when I tightened the valve core, but when I added a can of refrigerant with stop leak and a visible light dye in it, I stood there and watched the dye and a tiny bit of oil bubbling from the valve, then it suddenly stopped.

If you are going to do this yourself, I would recommend that you get the better set of gauges from your autoparts store. They will run $80-100 but in the long run, you will be glad you did this. You do not want to overcharge your system, it will damage the compressor.

You probably have not run the A/C often enough to keep the seals lubricated, putting on only 500 miles a year.

Thanks for the help.
You said…Before you use a refrigerant with PAG oil, make sure your system uses PAG oil in the first place.
Yes, when it was changed to R134a (obviously the R12 was recovered first by the shop), the sticker stated PAG oil was used.
Which brand of stop leak were you using? Do you have any recommendations of the best to get? How long ago did you add the stop leak? Has your system been running fine since you added it? Like anything else, there must be good brands and junk brands of this stuff.
To Whitey:
Since the leak is so very small (maybe 1 lbs in two years), I wouldn’t be adding freon every day, as you stated. As far as wasting money…yes the optimum choice is to fix it, but since I drive it maybe 400 miles per year, it would probably take quite a few years of adding cheap R134a refrigerant to equal $1,000 plus in compressor and discharge hose replacement cost. So unless something catastrophic happens…I’m saving money.
As far as being a hack solution…that is the only thing you got right!

With automotive A/C systems, small leaks don’t stay small very long…Especially compressor seals…But it’s worth a try, blow a couple of cans of gas in there and see what happens…The oil tends to pool and stay in the compressor. You should not need to add any. A small amount maybe…Do you have any idea how much freon is in the system now?? Is there ANY freon in the system now…

I second what caddy man says. I have not found AC leaks that are small… and stay small. It is a system under pressure. once they leak, it’s gone. also, the mentioned 500 miles a year should be killing the seals as mentioned.

I believe the unit holds 2lbs…not really sure since it was an AC shop that just recently did the retro fit and put in the R134a . As stated, the leak is very slow so I would think that it is close to full at this moment.
Cappy208: I Agree, but since I drive the car so little, I try to run the system for 10 to 15min a week at full blast just to try to keep up the seals and battery charged.

Have either of you had any experience with the stop leak that Keith had mentioned?

I just did this the other day. I had charged the system at the beginning of last summer but the performance had been going down the last couple of weeks. I think I used Sub Zero but not sure but it was the other day that I observed the leak actually stopping.

I knew that the low pressure valve was leaking before I started, but I still had a lot of refrigerant in the system so I didn’t want to discharge it into the atmosphere to replace the valve core. It stopped when I tightened it, used spit to confirm, but started leaking again when I topped off the system. Looks like the stop leak is doing its job in this case.