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2000 93 SE Vert Auto 2001 93 SE Vert 5spd
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Discussion Starter · #1 ·
Replaced the AC components and now I can't pull a vacuum. Tried using smoke and listening to find the leak, but to no avail. When I close the gauges at the high & low connections on the car, I do get a vacuum so I feel confident that it is the AC system not the vacuum pump or gauges.

How do I go about finding a leak in a non pressurized AC system?

Thanks.
 

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2000 93 SE Vert Auto 2001 93 SE Vert 5spd
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Discussion Starter · #3 ·
I can get no vacuum, even if I let the pump run for a several minutes.

I double cenecked the connections at the receiver, expansion valve and compressor. I am starting to think that the evaporator may have a leak. My other guess is that the expansion valve is not seated properly as it was difficult to get at, but I did not see it drawing in any smoke when using incense to look for a leak.

From what I have read, the use of a dye will only work if added to a semi-charged system, so I ordered some freon with dye to try to find the issue. However, the freon will not get here until early next week so I have some time to do some other troubleshooting (and maybe keep myself from creating more trouble).
 

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If you can't pull a vacuum at all I'm not sure how well that'll work, but the only other thing I've got is a pressure test with something like nitrogen or CO2. If the leak is in the evaporator, dye may not help... you might need a sniffer or something. Sorry this isn't easier!
 

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2000 93 SE Vert Auto 2001 93 SE Vert 5spd
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Discussion Starter · #5 ·
Thanks. Looks like my first foray into the AC world is not going as smoothly as I had hoped.

I used a flush on the lines and evaporator and wonder if that damaged something. Perhaps the issue all along has been the evaporator - I had a Volvo V70R that had that problem.

Could I use compressed air instead of nitrogen or CO2 and hook it up to the low side? Maybe use the old receiver/dryer to help keep from contaminating the new one?

It looks like the low side connection goes to the evaporator before going to the compressor, but it is a bit hard to tell, so maybe I can put some pressure into the low side to see/hear if there is a leak in the evaporator?
 

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I don't specifically know why, but I've always read you need to use an inert gas for this. Could just be to prevent contamination, but maybe there is some larger reason. You can buy CO2 and N cartridges for soda machines and beer brewing... you would probably need some sort of thread adapter to hook it up to the manifold gauge. I don't know how much you'd need.... probably not much, given the size of the leak/you don't need much pressure.
 

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You could also buy some caps to try and isolate parts of the system... Although I am embarrassed to admit I don' know what the various connections are... I've never paid attention!

Also, if the flush did hurt something, that something was already gonna fail.
 

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2000 93 SE Vert Auto 2001 93 SE Vert 5spd
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Discussion Starter · #8 ·
As always, thanks for the advice. I have a few other projects lined up for the next few weekends, so I am going to do some more research and let this stew for awhile before I take any action. I have already started to resign myself to the possibility of taking the car to a professional.

At least my other Saab has a working AC, so it is not essential that I get this sorted straight away.
 

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I had the exact issue about a month ago. I replaced the compressor, dryer and expansion valve. I had the same issue - could pull a partial vacuum when the pump was running, but immediately lost it when the pump was shut off.

I had leaks at the connection to the top of the compressor and at the expansion valve. I tried multiple times to install the compressor connection after the compressor was installed, but continued to have leaks. The only way I could get the compressor connection tight was to remove the compressor, attach the top plate with the two pipes and then juggle the whole assembly into place and reconnect the pipes to the rest of the system once the compressor was installed. I did pull the radiator and turbo hoses off to be able to do this.

The original o-rings on the expansion valve were larger than the replacements I got. It took me about 4 tries before I realized this and got fatter o-rings.

I found these leaks by pressurizing the system with air at 50 psi and listening with an ultrasonic leak detector. I believe someone with good hearing would have easily located them or soap bubbles would have worked. I just happened to have the tool.

I hated to put air in the system, but could see no other way. I actually bought a $20 helium balloon kit at Walmart, but was unsuccessful with it. Since I pressurized it with air, I put a vacuum on it overnight to insure all moisture was boiled off before charging it. I am confident my system is as clean and dry as it would have been taking it a local shop.

At this point, the A/C has never worked better in the 8 years I've owned the car.
 

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2000 93 SE Vert Auto 2001 93 SE Vert 5spd
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Discussion Starter · #11 ·
Thanks for sharing the experiences, TN_Explorer. I will try to put pressure in the system in a week or two after I get some other projects done.

I noticed that the O-rings that came with my AC kit were generic and did not match up exactly with the ones that came off. I tried to save the originals, but I think some found their way into the trash. I have SAE and Metric O-ring kits so I will try to find better matches.

To get the connections on the top of the compressor I did remove the turbo hose, but did not remove the coolant hose. I thought about it, but I just recently replaced the radiator and did not want to have to buy more coolant (I work in the driveway and drained fluids always get contaminated). Of the two O-rings, I could verify one was properly seated but was not able to verify the other. I also used the bolt that came with the compressor which was slightly shorter than the original, but had a smaller nut size making it easier to fit with the coolant hose on. That compressor was a PIA to get into place, but it looks like I might have to do it again using your methodology.

Per another thread concerning the evaporator, I believe my evaporator connection had some play and from what I can tell it should have none - I didn't give it much thought at the time. I plan on removing the expansion valve to better get a feel for the play. If there is a lot of play, then the evaporator may be the culprit. The original expansion valve took some force to remove once I got all of the bolts off and I may have broke a connection at the evaporator during the removal process.
 

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I also used the original (short) compressor bolt.

I had the exact same experience with the expansion valve. It uses four different size o-rings and I could not for the life of me get a replacement OEM set. Tighten all the connections snugly on the expansion valve and compressor. The guidance to "hand tight plus 1/4 turn" doesn't apply to these fittings, just the pipe joint connectors. The o-rings I used were a snug fit in the expansion valve - then I oiled them, fit them to the pipes, and assembled it. I snugged the bolt down (but I grab the ratchet near the head and don't put a lot of torque on fittings - especially in brass and aluminum).

My suspicion is your leak is o-rings - best of luck with it!
 
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