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Thread: Leak testing AC running R152

  1. #1
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    Leak testing AC running R152

    My AC system has a very tiny leak and I've been unable to find it. I suspect it's the voltage regulator (Used in 1988 and 1989 cars under the hood that balances the charges between the rear and front lines) but wanted to be sure.

    Since I'm running R152 is it possible to leak test it using an R134 leak test cans sold at Walmart then vacuum it out and recharge with R152? Both refrigerants are compatible with PAG-100 oil but I'm assuming the "Never mix refrigerants" rule still stands?

  2. #2
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    Hakeem, have you tried just using soapy water in a spray bottle?

  3. #3
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    Suck it out. Recharge with nitrogen, locate the leak using 'Snoop'
    Repair, retest.
    Then pump out the nitrogen, pull a vacuum and recharge.

    That's how I would do it.


    Sent from my iPhone using Tapatalk

  4. #4
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    Quote Originally Posted by jeffcfp1 View Post
    Hakeem, have you tried just using soapy water in a spray bottle?
    I have used it to find my other leaks but had no luck finding this leak using that method. I imagine it could be my regulator but I wanted to be sure.

    Quote Originally Posted by magnetchief View Post
    Suck it out. Recharge with nitrogen, locate the leak using 'Snoop'
    Repair, retest.
    Then pump out the nitrogen, pull a vacuum and recharge.

    That's how I would do it.


    Sent from my iPhone using Tapatalk
    Thanks. This sounds like the best bet. Any idea where I could source some nitrogen to leak test? Also I don't think I've ever heard of "snoop" how's it used?

  5. #5
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    You had mentioned that you repaired the diaphragm on the regulator. I question how successful such a repair could be.
    FWIW, my leaks were in the compressor and where the pressure cut off switch screws into the receiver/dryer.

  6. #6
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    Quote Originally Posted by jeffcfp1 View Post
    You had mentioned that you repaired the diaphragm on the regulator. I question how successful such a repair could be.
    FWIW, my leaks were in the compressor and where the pressure cut off switch screws into the receiver/dryer.
    Thanks for the tips. I’ll take it apart and look at it today but I’m almost sure I’d need to replace it since the glue is hard and prevents it from flexing. I’ll also need to check my connections again and when you say on the compressor do you mean the connections or the compressor itself?
    When vacuum testing it dropped to 28 overnight so it’s a small leak. I’ll be sure to taking you guys’ tips.

    I also took my insulation off and found my bulb hanging like this which was the causes of the bad front temps. Did you attach it further back on the straight section of the pipe or did you attach it at an angle close to where it bends to connect to the pipe on the firewall?
    95B82DA3-67EB-4941-B701-29BF26B09C60.jpeg
    Attached Images Attached Images

  7. #7
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    There you have a hack/naďve install, presumably by the p.o. No temperature change on the return being conveyed to the TXV. I would attach as far from the housing and as close to the bend w/o sacrificing full contact with the return. And, just learned, make sure the screw for the hose clam is on the underside versus top - if too close to the box it will be very difficult to remove the electronic connector piece that houses accommodates the two plugs for power/communication and resistor/transistor that controls fan speed. I just replaced mine. Also, upon reinstalling, ended up with a short as the bottom of aluminum heat displacing baffle on this piece (that the transistor is mounted on) was likely in contact with the 1/8" wire tube to the regulator.

  8. #8
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    Quote Originally Posted by hakeem43020 View Post
    I have used it to find my other leaks but had no luck finding this leak using that method. I imagine it could be my regulator but I wanted to be sure.



    Thanks. This sounds like the best bet. Any idea where I could source some nitrogen to leak test? Also I don't think I've ever heard of "snoop" how's it used?
    https://www.swagelok.com/en/catalog/...4&language=en&


    Fancy soapy water. But makes very small bubbles from small leaks.

    Nitrogen gas? And welding supply shop.
    We have bottles at work. I just use them and a pressure regulator.


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  9. #9
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    Quote Originally Posted by magnetchief View Post
    https://www.swagelok.com/en/catalog/...4&language=en&


    Fancy soapy water. But makes very small bubbles from small leaks.

    Nitrogen gas? And welding supply shop.
    We have bottles at work. I just use them and a pressure regulator.


    Sent from my iPhone using Tapatalk
    Oh I know what you're talking about, my dad has a few bottles down stairs that he uses to weld. I just have to figure out how to attach them and I'm good to go. I'll also be sure to use snoop when testing for leaks. Thanks so much, I'll report back when I get a chance to tinker with it. Is there a max amount of nitrogen to add? I heard I shouldn't go over 150 on the low side?
    Last edited by hakeem43020; 09-25-2017 at 11:32 PM.

  10. #10
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    Leak testing AC running R152

    Quote Originally Posted by hakeem43020 View Post
    Oh I know what you're talking about, my dad has a few bottles down stairs that he uses to weld. I just have to figure out how to attach them and I'm good to go. I'll also be sure to use snoop when testing for leaks. Thanks so much, I'll report back when I get a chance to tinker with it. Is there a max amount of nitrogen to add? I heard I shouldn't go over 150 on the low side?
    I just use 40 - 60 psi. No need to get crazy. You’re only looking for a leak.



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  11. #11
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    Leak testing AC running R152

    Got a 5 speed conversion done to my ‘89, took a while but it’s finally completed!




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  12. #12
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    Quote Originally Posted by Quantumleap View Post
    Got a 5 speed conversion done to my ‘89, took a while but it’s finally completed!






    Sent from my iPad using Tapatalk
    Hey congrats! Did you do it yourself or have it done? I see it's sitting in front of the service center . I did it myself with the help of my friend. Did you keep the same diff and what did you use for a tranny? Diff Gear ratio?
    '88 635, '92 325IC

  13. #13
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    As inexpensive as R152a is, I'd probably use that to test for leaks. Hopefully, you can spot with it some soapy water, and the leak isn't in a hidden part of the system (like the evaporator or exansion valve.

    I like to use this stuff on all the fittings:

    https://www.amazon.com/dp/B008HOSQQQ...a-322766917873
    Dean
    Lutz, FL

    '85 635 CSi Euro #9402254
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  14. #14
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    Quote Originally Posted by carsnplanes View Post
    Hey congrats! Did you do it yourself or have it done? I see it's sitting in front of the service center . I did it myself with the help of my friend. Did you keep the same diff and what did you use for a tranny? Diff Gear ratio?
    I had it done,my mechanic’s wife’s car was a wrecked ‘85, took everything out of that car and put it in mine, replaced clutch and seals, plus new flex joint

  15. #15
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    Quote Originally Posted by Quantumleap View Post
    I had it done,my mechanic’s wife’s car was a wrecked ‘85, took everything out of that car and put it in mine, replaced clutch and seals, plus new flex joint
    Awesome...my 5 spd swap running gear came out of an 85 I used to have also. I just didn't take the diff out. Still kicking myself. Only had time to take the passenger seat out. Left the driver's in there, sport seats...really kicking myself. I need a driver's sport seat.
    '88 635, '92 325IC

  16. #16
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    Quote Originally Posted by carsnplanes View Post
    Awesome...my 5 spd swap running gear came out of an 85 I used to have also. I just didn't take the diff out. Still kicking myself. Only had time to take the passenger seat out. Left the driver's in there, sport seats...really kicking myself. I need a driver's sport seat.
    Awesome, my mechanic said the auto’s differential is nicely geared, short 1st gear and puts power down nicely...ratio is 3.91, very quick acceleration. Would love those sport seats as well, too bad they’re hard to find and over a grand a set

  17. #17
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    If it’s a very tiny leak well it will be hard to find without nitrogen. The more pressure unrest with the easier it will be to find a leak. How much pressure can u use in a car AC system. We test building hvac systems with up to 400psi so it’s easy to find even small leaks. I’m pretty sure there is an internal leak sealer product u can use if the leak is difficult to find. I’ve never used one but it could be worth investigating.
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  18. #18
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    I've seen AC manifold sets leak that small amount before, double check that is not your source

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