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Should I use pressure test to check for leaks, or just vacuum?


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DeathTongue
Novice

Jul 16, 2015, 10:37 AM

Post #1 of 19 (1738 views)
  post locked   Should I use pressure test to check for leaks, or just vacuum?  

2004 Pontiac GTO - 5.7 LS1 engine, 86K miles.

I have to recharge my AC system, and I want to be sure to do this using the best procedure, since I have a brand new compressor and don't want to mess it up. I gather than I need 2 cans of R143a and 1 can of oil, approx., and that I need to check for leaks first. On youtube I see some mechanics pressurizing the system to around 150 psi to check for leaks, while others just see if it will hold the standard 30 inches of vacuum. Is there a reason to do the pressure test in addition to the vacuum check?


Also, I still need to do some research on this, but should i put the oil in on the low side after the R134a? should engine be off or running when oil goes in?

thanks in advance!!


Hammer Time
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Jul 16, 2015, 11:42 AM

Post #2 of 19 (1732 views)
  post locked   Re: Should I use pressure test to check for leaks, or just vacuum?  

What happened to the original compressor?



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DeathTongue
Novice

Jul 16, 2015, 11:52 AM

Post #3 of 19 (1726 views)
  post locked   Re: Should I use pressure test to check for leaks, or just vacuum?  

I had a bad compressor (grinding noise), so it was replaced by my regular mechanic, who is very reputable, but not an AC specialist. When he was done, it was only blowing air about 22 degrees cooler than outside air, and the low side pressure was only 95, high side around 160 or so. It's been about 30 years since I worked as a mechanic, and I never did have much ac experience, so I'm really trying to learn fast here. I want to go ahead and evac and pressure test, then recharge with the normal amount of r143a and oil.

Several people on other sites have told me that since the mechanic who put it on didn't change the dryer and evaporator, this compressor is already toast, but that seems a little extreme. Anyway, I want to try to get this charged properly before I try to replace any other parts or take it back to have my guy look at it.


Hammer Time
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Jul 16, 2015, 12:03 PM

Post #4 of 19 (1724 views)
  post locked   Re: Should I use pressure test to check for leaks, or just vacuum?  

No, that's not extreme at all. He's almost right. It's the condenser you have to change, not the evaporator. When that compressor let go it contaminated the system and the condenser was on the receiving end.

You also need to know exactly how much oil is already in the compressor and how much you need to add. I can see you doing this job all over again in the near future. AC repair requires extensive knowledge.

You also need to find out what made the first one fail or it will happen again.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



DeathTongue
Novice

Jul 16, 2015, 12:12 PM

Post #5 of 19 (1720 views)
  post locked   Re: Should I use pressure test to check for leaks, or just vacuum?  

Well, I do want to get AC experience, so doing the job over and over might accomplish that. But, I would prefer to do this job once only if possible.

At this point, with the only option being me doing my best to address the situation, would my best bet be to change the condenser before I do anything else? This compressor has only been run for about 50-100 miles since the work was done, so either I can get it fixed, or I will take it back and have the whole job done over again by someone else if I destroy it in the process. Also, about the oil, will the oil not pull out of the compressor when I do the purge?


Hammer Time
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Jul 16, 2015, 12:48 PM

Post #6 of 19 (1717 views)
  post locked   Re: Should I use pressure test to check for leaks, or just vacuum?  

No, it will not. Some oil will be mixed with the refrigerant when you recover it but the vacuum doesn't pull anything out.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



DeathTongue
Novice

Jul 16, 2015, 1:02 PM

Post #7 of 19 (1715 views)
  post locked   Re: Should I use pressure test to check for leaks, or just vacuum?  

so, if the mechanic added oil to the compressor just a few miles ago, it should still be there even after I purge the system?

I realize this is not the optimum way to do things, but if I have to take it back to a pro, I will be going until next spring without AC, and it's 100 degrees here in the summer. If I can get this working good for 1000 miles, which would last me til spring, then that would work. If it works for more than that, bonus. Since I do have a decent set of mastercool gauges and a vacuum pump, I would really like to see what I can do with this, even if it's just a stop-gap measure. In fact, I would be fine with buying a Robinair leak detection kit if a leak shows, and then fixing whatever I can, but I really do not want to remove this compressor. thanks for your help!


Hammer Time
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Jul 16, 2015, 1:34 PM

Post #8 of 19 (1710 views)
  post locked   Re: Should I use pressure test to check for leaks, or just vacuum?  

Who knows how much he added?

I would add about 3-4 ounces because of the condenser and dryer change. Adding it during vacuum is the best way.
I hope those are 12 ounce cans you have with no additives in them because this holds exactly 24 ounces.



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DeathTongue
Novice

Jul 16, 2015, 1:39 PM

Post #9 of 19 (1708 views)
  post locked   Re: Should I use pressure test to check for leaks, or just vacuum?  

thanks for the info. I think I have enough now to at least not make things too much worse. I'm going to get some cans of the regular Speed Steed R134a at walmart and weigh them to make sure the ones I use both weigh the same, and hope that's close enough.

One other thing, since this car was manufactured in Australia, does it have the same normal set up of parts that you would have in a US made car?


Hammer Time
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Jul 16, 2015, 4:24 PM

Post #10 of 19 (1696 views)
  post locked   Re: Should I use pressure test to check for leaks, or just vacuum?  

I don't know. I've never worked on Australian cars.



Quote
I'm going to get some cans of the regular Speed Steed R134a at walmart


I hope that is regular, virgin R134A and not some gimmick substitute.



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Discretesignals
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Jul 16, 2015, 4:32 PM

Post #11 of 19 (1694 views)
  post locked   Re: Should I use pressure test to check for leaks, or just vacuum?  

The POS over priced GTO that sold here in the states is built over in Australia. Same car. Go figure...lol I did a clutch job on one a few months ago. Price for parts are outrageous.





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(This post was edited by Discretesignals on Jul 16, 2015, 4:36 PM)


Hammer Time
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Jul 16, 2015, 4:35 PM

Post #12 of 19 (1690 views)
  post locked   Re: Should I use pressure test to check for leaks, or just vacuum?  

Oh, that's what he meant because he's in Texas, not Australia.



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DeathTongue
Novice

Jul 16, 2015, 5:34 PM

Post #13 of 19 (1686 views)
  post locked   Re: Should I use pressure test to check for leaks, or just vacuum?  


In Reply To
The POS over priced GTO that sold here in the states is built over in Australia. Same car. Go figure...lol I did a clutch job on one a few months ago. Price for parts are outrageous.


they were overpriced at $35,000 new, but I got this 85,000 mile car for $10K, and the quality is pretty nice. I've been a big GM and Pontiac fan for years, but this car is built better than any I've driven before, and the attention to details like the great seats, padded armrests and auto headlights are pretty cool. Parts can be expensive though.


In Reply To




.


Quote
I'm going to get some cans of the regular Speed Steed R134a at walmart


I hope that is regular, virgin R134A and not some gimmick substitute.


Yes, it's the cheap bulk cans of store brand R134a, nothing added, they work with both kinds of taps valves.





.

In Reply To
Oh, that's what he meant because he's in Texas, not Australia.


yes, the reason I ask is because with my limited AC knowledge I've heard there's two different types of systems with different valves, and maybe other different parts. Back when I was working as a mechanic my job was mainly to take engines out of old cars and rebuild them with as many of the old parts as possible, so I'm pretty good at that type of thing, but with AC systems I've maybe worked on them twice and that was many years ago, so I barely know what some of the parts are and what they look like. I'm doing as much research as my work allows, but a quick search of autozone shows that these parts are used for my car, should I replace any?: accumulator, receiver/dryer, expansion valve? but no condenser is listed on their site. I may have to call the radiator supply house for that part and see what they have. Looks like there are some online I can order if I have to. well, thanks for all the comments so far, I do appreciate the help, and the good advice also, because I like to do things as safely as possible.


:)


Tom Greenleaf
Ultimate Carjunky / Moderator
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Jul 16, 2015, 8:34 PM

Post #14 of 19 (1679 views)
  post locked   Re: Should I use pressure test to check for leaks, or just vacuum?  

Note/warning: Was just at a Walmart and checking prices for 134a in 12oz cans. All was junk with additives except 2 cans. Wasn't there for that and little time but the two were cheaper and said is like 134a? What? If there's a product that "behaves'' like the real thing and uses those exact acronyms, 134a (pure) isn't fair! Yes there's a 152a (also sold as computer duster) that can work but don't go there till sold as pure and for A/C.
Price isn't the major deal with 2 cans - right product is. Sorry I can't confirm what I saw as the area was full of the junk you DO NOT want caught my eye more,


T
PS: [134a] Chemical name is....... 1,1,1,2-Tetrafluoroethane - the brand really shouldn't matter.......
PS2: "Speed Steed" was listed and shows as the correct stuff! READ IT carefully.........




(This post was edited by Tom Greenleaf on Jul 16, 2015, 8:43 PM)


DeathTongue
Novice

Jul 18, 2015, 6:13 PM

Post #15 of 19 (1647 views)
  post locked   Re: Should I use pressure test to check for leaks, or just vacuum?  

OK, I had to take back the HF pump because it would only pull about 25 inches of vacuum. I rented a pump from Autozone and that pump worked a lot better, and pulled 28 inched of vacuum pretty quickly. The system held the vacuum for 30 minutes without the gauges moving so I was ready to recharge. I added a couple of ounces of Pag 150 oil, then the 2 cans of R143a. the weight of the cans was 15.0 and 14.9 ounces full, 3.3 ounces empty, so it looks like I got about 23.3 ounces, which is close to the proper amount of 24 ounces. Now, my low side pressure is around 40, high side is around 220. Air temperature out of the front vent is 50 degrees on the second fan setting, 56 degrees on the 3rd fan setting (out of 4, I didn't test it on max). Outside temperature is 93 degrees with 42% humidity. So, it seems to be working good for now. I will post again if I have any problems. thanks for all the advice!


DeathTongue
Novice

Jul 18, 2015, 6:56 PM

Post #16 of 19 (1646 views)
  post locked   Re: Should I use pressure test to check for leaks, or just vacuum?  

One final question. When I said my compressor went out, it was actually the clutch that went out, I'm not sure if I was clear on that or not. Does specifying that point change what parts should have been replaced?


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jul 18, 2015, 7:21 PM

Post #17 of 19 (1643 views)
  post locked   Re: Should I use pressure test to check for leaks, or just vacuum?  

Not really. Clutches usually fail due to internal compressor issues. Changing a clutch alone usually doesn't work out well.

Those pressures sound a little on the high side. Make sure the cooling fan is working properly.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



DeathTongue
Novice

Jul 18, 2015, 7:52 PM

Post #18 of 19 (1641 views)
  post locked   Re: Should I use pressure test to check for leaks, or just vacuum?  

the whole compressor and clutch assembly was replaced, it's just that the clutch was the part making the noise, which seems to be a common problem with GTO's. Right now it feels like an arctic zone in there, even better than our Grand Caravan, hopefully it will continue to work great, at least til next spring.


Hammer Time
Ultimate Carjunky / Moderator
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Jul 18, 2015, 7:54 PM

Post #19 of 19 (1640 views)
  post locked   Re: Should I use pressure test to check for leaks, or just vacuum?  

OK, I'm going to close this now as solved. You can ask any Mod to reopen it if necessary.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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