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Help with Troubleshooting AC leak
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blue_can
New User
May 19, 2011, 10:00 PM
Post #1 of 4
(3366 views)
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Help with Troubleshooting AC leak
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Hi – new to this forum and looking for some help on diagnosing a leak on my car’s AC. The vehicle is a 2000 Chevy Metro with about 125K miles. This problem actually started when the car was only about 3 years old – I’ve owned it since it was about a year old. Being lazy I would simply recharge the system every 3 years or so. However, after not bothering to fix it and leaving it unused for the last 2 years I decided to finally get around to fixing it.
A couple of years ago I injected refrigerant with a UV dye bit never bothered to examine it under a black light until recently. The diagnosis was not very conclusive since it had been a while since I had injected the dye but it looked like there was a small amount of dye on a couple of the fittings.
Since I was going to be taking the system apart I decided to replace all the seals. I also removed the compressor and replaced the shaft seal. The compressor had what looked like oil around it so I figured the seals may have been leaking. I also flushed out the condenser and all the lines. I drained the compressor and replaced with new oil. I noticed that the compressor was low on oil. I also installed new schrader valves and caps.
After reconnecting the system I used a vacuum pump to get very close to 30” Hg vacuum. I let the pump run for half an hour and then closed the manifold gauge valve and observed the vacuum for 1 hour. There was no change in the reading so I figured the system was leak tight and recharged the system.
The system worked really well – the compressor was much quieter than in the past and was also cooling much better than in a long time. I found that some of the oil at some of the fittings had turned to a kind of gel so this could have been affecting performance.
This was about 2 weeks ago and it was working great for several days. Since the weather had cooled off I had not used it for about a week. It was hot again to day so I decided to turn it on and once again no cold air. Got home and checked the system and the condenser fan was not running. I decided to check the fuses and relays. They seems fine. At this point the condenser fan turned on and I also checked that the compressor clutch voltage line had the correct voltage.
However, there still was no cold air so I hooked up the manifold gauges and guess what – 10psi on the low side and 100psi in the high side. This is the same problem – what I’ve noticed is that the system leaks until the charge resulting in the reading I’ve mentioned gets to that level and then stops leaking. It never leaks out completely.
I purchased a leak detector today but I could not spot any leak detect signal in the system. The only place it alarmed a few times was at the cold air discharge inside the vehicle. I’m wondering if the leak is in the evaporator – also that’s once thing I did not take apart.
Any ideas on how to narrow down the problem?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 20, 2011, 4:05 AM
Post #2 of 4
(3355 views)
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Re: Help with Troubleshooting AC leak
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You mean an electronic leak detector? If it goes off inside at a vent that does strongly suggest evaporator but before you go dash diving (usually necessary to replace those) I might charge it up again to get pressures up, system working enough to produce condensate (water) and seek out usually a rubber elbow or let it drip on some plain white paper.
Dye or not that paper is your evidence as plain water would just dry. If oily anywhere and keep looking for oil anywhere refrigerant runs that's the spot highly suspect.
Electronic leak detectors will get confused sometimes (mine does) with fast air, windy days and something uninvolved like you just sprayed something or cleaned something. Hate to see anyone replace what isn't the problem and back to square one again.
I don't have/software to see what the layout of this system is. If heater blower is easy enough to remove sometimes you can see the evidence - can't be sure for all vehicles ever made.
FYI - a ONE week leak down which this seems to be should be easier to find. Back when it was a 3 year needed a boost would be near impossible IMO.
Don't be too fooled by dye as sometimes just hooking up gauges and removing them can spit on A/C parts and confuse the diagnosis. UV dye won't clean off well and takes quite a while to be completely gone from sight if some got where it shouldn't be accidentally.
Side note: Holding a vacuum is a good sign but keep in mind unless high altitude that the vacuum is sealing OUT atmopheric pressure of about just 16.7 PSI vs the operating pressure that can spike into the low 100s. Some leaks need more pressure to leak but it worked and circulated for a while so dye is probably present somewhere however leaks can be funky and choose what pressure to leak at and hold vacuum and not pressure.
Shaft seal already replaced doesn't mean it's good. It can leak behind clutch without seeing oil or UV evidence at first if slow. In that it needed it once the compressor's shaft bushings may allow some wobble and wreck a new one. Heck - it's easy to wreck a new one just putting one in. I won't do another myself as I've failed too many times (once) at those which was enough. Rebuilts fail all the time so it's a trouble spot with some miles and if you find it there or body gaskets of compressor go new - some are only chump change more that a reman.
Side note II: Plain static pressure - engine off should be roughly the same in PSI as the area real temp in Fahrenheit. Magical. If lower and it would be if much colder out normally it's empty for all intents and purposes.
One more and then on to more looking for the leak for you to do: The service ports do in fact rely on the caps for non Shrader type ones if applicable. Ball valve type especially are not as dependable IMO as Mr. Shrader's invention of his valve - a real name for the inventor. Check you new ones for leaks as that could still be faulty there,
T
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blue_can
New User
May 20, 2011, 8:48 AM
Post #3 of 4
(3344 views)
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Re: Help with Troubleshooting AC leak
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Thanks for the excellent response Tom. Yes I intend to recharge and try looking for the leak. Yes, as for the detector I was referring to an electronic detector. I know these things can give out false alarms so I would need more convincing before condemning the evaporator or the TXV. Hopefully I did not damage the compressor shaft seal while installing - I actually purchased the correct Kent Moore install tool as well as the shaft seal protector which should have kept it from getting nicked during install.
I will recharge today and try seeing if I can figure out what is going on. I was also wondering if the pressure release valve on the compressor could the problem - maybe it is blowing under pressure. But on the other hand when I examined it yesterday there was no evidence of oil around it _ I assume some oil may have also come out if it had released.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 20, 2011, 9:33 AM
Post #4 of 4
(3336 views)
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Re: Help with Troubleshooting AC leak
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Forgive me - I read a lot of this stuff and not just copy/pasting replies most of the time. Before if not too late, while there's still pressure in the system if the "blowout" valve is suspect try plain dish soap and water in a spray bottle. That has verified some rubber hose pin holes too small to see and a place that was so close to another I wanted to be sure - it worked. When you find one totally empty the book says you can use a tad of R-22 and nitrogen to find leaks. Truth is I don't like the idea as the molecules of 134a are smaller and would leak where other gasses might not - rock and hard place. Purposely venting 134a is illegal but purging lines is not as it can save a system. Face it - it all will end up lost sooner or later but saving as much as possible is still good.
Soapy water is just too difficult for most condenser leaks which should show oil stains if in the fins or bubbles at connections if there.
I love my electronic sniffer but you do have to get used to it. Check the service ports with caps off and again with caps on. All best done outdoors with little to no wind as if we can choose.
If it just quietly quit just fixing the leak short of other observations or reasons other items can be left alone. When it proves itself after proper charge and running it and lasts I like to put drop of penetrating (weak or just oil) on the flare type fitting to other things if applicable such that you have a chance to remove those later without twisting everything up. The alloys used about weld threads sometimes dammit! Can turn one item into a series of others that refuse to undo.
The deal with condensers is that high efficiency ones are a maze of pathways and when (doubt this case) they are trashed with debris inside flushing is near impossible - some not difficult or expensive as A/C goes.
Catching a noisy compressor if heard right away while still working and disabling it (right away) for replacement can save a lot of debris issues.
Again - your last operating pressures of 10L and 100H suggests there's some refrigerant in there for sure and compressor is compressing. Another again - with a couple oz of refrigerant or at full proper charge the static pressure would be the same so not an indicator of how much is in it which can't be known but tells you can still look for leaks which is by far the #1 reason for lack of cooling and the subsequent low charge.
Check out the top post of the A/C section - long but excellent on charging procedures.
Good luck - they are not all easy to find as you are finding out,
T
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