Giovanni

In the past the A/C on my shark would not hold charge after a week or so. Since then I used a few stop leak products but it seem not to help. Last week I replaced all th o-ring. I pulled vacuum last night and it got to 30hg in about 5 minutes. I disconnected the vacuum pump and let it hold vacuum all night. Twelve hours later it was 25 Hg and 23 Hg after another 12 hours. I suspect I have a small leak under the dash. Since SITM is next week I am desperate to get the a/c to hold pressure.

I am thinking about using a stop leak. Have you guys used this product with good result? http://cgi.ebay.com/ebaymotors/R-134...Q5fAccessories

I am planning on replacing the drier prior of charging and pull vacuum for at least 2 hours, probably overnight. The system should take about 36 oz of
R134a?

SharkSkin

Stop leak is one of an AC tech's worst nightmares. It can really screw up their equipment, and it can gum up your expansion valve and evaporator. What you really need is to flush the system completely, replace the oil, and replace all of the o-rings -- and probably the rubber lines as well, especially if they are oily near the ends. Most AC shops can rebuild the lines for $50 bucks each or so.

I'd say just wear shorts to SITM and pack a lot of drinking water. When you get back, pull out all of the rubber hoses and take it to an AC shop to have the lines rebuilt and the compressor/condensor/evaporator flushed. Then bring it home and put it all together.

I know it's easy to say that the damage is done since it's already had stop-leak added -- so what's the harm in adding more -- but you would really be a lot better off in the long run just fixing it right.

Giovanni

I am debating if I should remove the compressor and drain the oil this weekend. The hoses appears to have not leaks.

Bytheway, the vacum this morning was 22 HG this morning. Dropping from 30 HG to 22 HG in 36 hours is considered a big leak or small leak?

Mrmerlin

did you replace the O rings on the top of the compressor?? there should be 2 or 4 under the fitting that holds the lines.
Use green O rings

Giovanni

I was going through the o-ring illustrations in the manual book last night. Funny that you mentioned that. I'm removing the compressor tomorrow to change those o-rings and add new oil.

SharkSkin

Mine didn't drop at all in 24 hours. Note that the vacuum test is not conclusive. You may have leaks under vacuum that do not appear under normal system pressure, and vice-versa. Still, it's not a good sign. Ideally you won't have leaks either way.

Also, water in the system can cause the pressure to rise when you pull a vacuum. Applying vacuum for 5 minutes is not near long enough, an hour is considered minimum and I vacuumed mine down overnight to make sure all moisture was gone. You should probably go ahead and replace the dryer as you mentioned before performing this test.

JHowell37

Vacuum is not an appropriate method for finding leaks. The purpose of vacuuming is to remove moisture from the system. If you happen to find a leak while vacuuming, great, but it shouldn't be relied on for that purpose.

That stop leak **** will ruin the sight glass on your manifold gauges.

dr bob

The vacuum 'test' is really just a way to see if there are GROSS leaks, like you left a connection loose. "Full" vacuum at sea level is equal to about 14.7 PSI pressure difference, in the wrong direction for a real test. Consider that your low-side pressure under load is twice that, while high-side pressure can be twenty times that. ASSuming that the leak is the same size in both directions (bad assumption with o-ring connections) you charge will last an hour or two with the leak rate you are sharing.

Stop leak products are a nightmare, because they are hard to get out when you change your mind. They plug recovery equipment as well as they plug expansion valves, dryers and compressor valves. They do not plug leaky rubber pieces like o-rings and hoses, go figure.

O-rings at the expansion valve are susceptible to leaks because of the strain put on them by the hoses and lines against the firewall. Those lines MUST BE DETACHED from the firewall when you change the expansion valve and o-rings there. The suction lin through the fuel cooler is easier because you have that apart to change those two o-rings anyway.

O-rings in the rear system must be changed, including the connections to the front system, the pass-throughs where the lines come through the floor, the connections at the solenoid valve under the passenger seat, the lins to the rear expansion valve and evaporator. And those two hoses.


I typically recommend that you use polyolester oil on refill even if you initially plan to use R-12. It means you may be able to do a just-gas swap to R-134a later without a system flush.

You've remembered the 4 o-rings awhere the manifold plate attaches to the compressor. While you have the compressor out again, replace the schraeder valve cores in those twu unused charge ports with R-134a-compatible cores, and put new o-rings in the caps.

Oil up the o-rings, all of them in the system, as you install them. Do Not Overtighten the fitting nuts on o-ringed connections, and do not twist the fittings after they are snugged up. You'll distort the 0-rings if you overtighten, and will tear or gall the o-rings if they get twisted while under any pressure from the connector nuts.

Dirt is the enemy of all AC components and connections. If your hands are dirty after reassembling the parts and pieces, you are at risk of dirt damage and leaks from dirt on seals. No such thing as "too clean".

The seal in the front of the comressor is a mechanical seal that depends on a film of oil for both sealing and lubrication. After charging the compressor with oil and with the hoses attached, roll the compressor a few times by hand with the nose straight down prior to installation in the bracket. This will clear the cylinders of oil and get some spread in the seal faces.

Get everything as clean as possible, and include a UV leak detecting dye in your initial gas charge. Use a real UV light source in a dark garage to inspect your system soon after you've charged it. It's an easy way to find bigger leaks. If you can borrow one, get a good electronic sniffer and go around each connection to find any stray gas leaks. A plastic bag, wrapped around a connection, will capture fugitive refrigerant from small leaks, allowing the sensor probe to read them if it is inserted into the bag.


Good AC performance is the result of diligence and care, along with using the proper tools, parts and technique. It isn't really complicated, but it is time consuming.

Giovanni

Both pressure switches had worn out black o-rings and one was leaking. Compressor had no oil, now it does and its reinstalled. I flushed the whole system till no residue was coming out. I will pull vacuum tonight and cross my fingers for tomorrow.

Giovanni

Bytheway, my compressor is a Seiko Seiki SS-170PVS5. The compressor was very easy to remove and put back. Probably took me 10 minutes to reinstall it.

Andy E.

This is 100% true.

The proven and acceptable manner in finding a leak within a sealed refrigeration system is to use pressure and lots of it. In the refrigeration industry, nitrogen is used and regulated to achieve approx. 300-350 PSI test. An ultrasonic leak detector can then be used to detect smaller leaks that would normally go unnoticed.

In the past and way before the new environmental restrictions, techs used to "azeotrope" or mix a little R-12 into the nitrogen so that the standard leak gas detectors would pick-up a scent. With the advent of the ultrasonic leak detector, this is no longer practiced.

Also, as Sharkskin said a vacuum pump must operate for at least a few hours so that all moisture has been removed from the system.

SharkSkin

Gio, what did you flush it with? How did you ensure that whatever you flushed it with is 100% gone?

Giovanni

I did the vacuum to find how bad the leak was, not to find where the leak was coming from.

Dave, I used denatured alcohol with the compressor's hoses disconnected and the drier disconnected. I used enough alcohol to get everything cleaned out (probably not even 10 tspn). After I was done I disconnected the upper and lower connectors of the condensor and blew some more, nothing came out so I hope I blew enough air in the system to get out everything else. I blew air for about 2-3 minutes.

SharkSkin

That should be OK, the denatured alcohol should evaporate off when you pull a vacuum, though it may or may not have cleared out the stop-leak. I have heard of some people having some success using mineral spirits as well, but I don't know what the risks are with that. Definitely replace the dryer before the next step. If the dessicant starts to come apart it will fill the system with dust.

Giovanni

I filled the system Sunday morning but the vent temperature (on Maximum setting) would not get colder than 75 degrees at idle. So I said screw it and i'll drive the car on Monday and see how it does. I had it on Maximum for about 5 minutes and then I turned it to Medium and finally to Low since it was blowing pretty cold. Not bad for a flush, new rings, vacuum and 3 cans of r134a (KNOCKING ON WOOD).

Now I can take the a/c stop leak thingy back to walmart to get my $20.00 refund since I did not need it, hehehhe.

SITM, here we come!!! again, knocking on wood