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How Long Can My AC System Sit with No Vacuum and no 134a?

lambertjohn on Wed September 07, 2011 12:10 PM User is offline

Year: 1996
Make: Volkswagen
Model: Golf
Engine Size: 2.8
Refrigerant Type: 134a
Country of Origin: Mexico

Well, after a lot of hard diagnostics work, I finally discovered the reason my newly renovated AC system won't hold a vacuum is because my evaporator has a leak in it. And I'm guessing it's a sizeable one due to the fact that I can't hold a vacuum for more than 3 seconds.

A little bit of history. I had a failed compressor in my 96 VW. So I purchased a new compressor, condenser, drier, and expansion valve. I then went in and flushed all the hoses as well as the evaporator. Put everything back together with new 0-rings and attempted to pull a vacuum. The best I could get on my gauge was 10" and I would lose it the minute I shut the vacuum pump off.

So now I have a leaky evaporator. How did I deduce that my evaporator has a leak? Well, I had some help from some nice folks on this forum. What I did was disconnect the expansion valve from the evaporator inlet/outlet pipes. Then I hooked up my vacuum and gauges to the high and low port valves, plugged the ends of the port hoses (the ends that originally went into the expansion valve) , and drew a vacuum on everything forward of the firewall. It held a perfect 29" vacuum. I was ecstatic...and bummed at the same time.

In order to install a new evaporator, I need to take on the arduous task of completely dismantling my dashboard, which means removing about a thousand nuts and bolts, the glovebox, the steering wheel, the radio, the vents, all of that stuff. And I have to hope I can get it all back together properly. Lord have mercy on my soul.

I'm going to tackle the job, just not right now. What I'm going to do is go ahead and put the new expansion valve back in, connect it to the evaporator and high/low ports as it should be with new o-rings and tighten everything down. So essentially, my AC system will be returned to one fully assembled unit. Just a non-working one. Then I'm going to take a break for a few weeks and get my bearings oriented on this dashboard removal thing I have to go through.

Now my question...

Will anything be damaged within my new system for those weeks that it's just sitting in my car connected but doing nothing? Internal rust? Moisture problems? Acid buildup? I know I have to install a new drier when I finally do go in and swap out the evaporator, but other than the drier, are all the other components going to be okay with no vacuum drawn and no 134a running through the system? Again, everything will be connected as if it were a fully functional system, it will just be a non-working unit until I can get the evaporator swapped out.

Last question, anyone know a good source to get a quality evaporator for my 96 GOLF with 2.8 engine?

Thanks all. This forum has been invaluable in my quest for cold air in my VW. I really appreciate it.

Edited: Wed September 07, 2011 at 12:27 PM by lambertjohn

HECAT on Wed September 07, 2011 1:19 PM User is offline

Try and perform this same test on the evap to be sure the TXV connection point was not the leaking culprit.


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


lambertjohn on Wed September 07, 2011 2:16 PM User is offline

Thanks for the tip! If I'm reading your response correctly, you're asking me to pull a vacuum on the evaporator? And if it pulls 29", then the leak is in my expansion valve or its corresponding o-rings? Am I interpreting your advice correctly?

mk378 on Wed September 07, 2011 3:46 PM User is offline

Right, since you replaced the expansion valve, the connection between the valve and the evaporator may not have been made up properly. Whenever a repaired system fails the vacuum leak test, the first place to suspect is any connection that has been worked on.

Also you should use mineral oil or Nyloq, not PAG oil, on o-rings. PAG oil does bad things when exposed to air and moisture, it should only be used inside the system as compressor lubricant.

Edited: Wed September 07, 2011 at 3:47 PM by mk378

lambertjohn on Wed September 07, 2011 11:42 PM User is offline

Great advice on the 0-rings. Unfortunately, my car is all back together and everything is installed. And as they say in Texas, "it aint comin apart again." Funny thing, I rebuilt the AC on my Honda Accord several years ago and coated the o-rings with Pag oil. Never had a problem with it. Still works to this day. So when you say PAG oil does "bad things when exposed to air and moisture," I can't imagine what those bad things are. I guess if the bad things stay away for a few years, I'm okay with that. Anyway, thanks again for the advice. Noted and filed.

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