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Discussion Starter · #1 ·
Do these LBZ AC systems lose AC Charge R134a over time, or am I going to need to look for a leak? If so how is the best way, Do a Vacuum leak down test, and also charge with Nitrogen and check for pressure drops? thanks!
 

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Do these LBZ AC systems lose AC Charge R134a over time, or am I going to need to look for a leak? If so how is the best way, Do a Vacuum leak down test, and also charge with Nitrogen and check for pressure drops? thanks!
No a/c system will go low on refrigerant without a leak.

Adding dye to the system and using a black light is the most widely used/accepted method currently.
 
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Discussion Starter · #3 ·
No a/c system will go low on refrigerant without a leak.

Adding dye to the system and using a black light is the most widely used/accepted method currently.
thanks! The High side test port with the ball valve was left uncovered (dust cap off) and mud and crud was allowed to fill that port, the previous owner passed so I cannot ask him, I will ask his mechanic today though to see what all was done and why that left off, I have a sneaking suspicion that the high side ball valve was leaking and they abandoned the repair as the previous owner was terminally ill.

How about Nitrogen for leak checking? And will the vacuum/ and holding vacuum be a sign of leaks? thanks!
 

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As ChevyTech said, put dye in the system, charge it up and run it a while. If that high side is leaking you will see it around the schrader valve or other areas that are leaking. That is what I did on my LBZ with 349k miles. Mine was leaking from the high side hose connector. I replaced the hose, pulled a vaccum, filled it up with a little bit of oil and 134A - been icy cold ever since.

In this pic you can see how dirty the hose was from the oil and dye that was leaking out:
1091516
 
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Discussion Starter · #5 ·
As ChevyTech said, put dye in the system, charge it up and run it a while. If that high side is leaking you will see it around the schrader valve or other areas that are leaking. That is what I did on my LBZ with 349k miles. Mine was leaking from the high side hose connector. I replaced the hose, pulled a vaccum, filled it up with a little bit of oil and 134A - been icy cold ever since.

In this pic you can see how dirty the hose was from the oil and dye that was leaking out:
View attachment 1091516
ahh yes I can see that. This truck has been oil undercoated, the whole underhood already looks like that, hoses, under the hood and inner fenders. great!
 

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Discussion Starter · #6 ·
As ChevyTech said, put dye in the system, charge it up and run it a while. If that high side is leaking you will see it around the schrader valve or other areas that are leaking. That is what I did on my LBZ with 349k miles. Mine was leaking from the high side hose connector. I replaced the hose, pulled a vaccum, filled it up with a little bit of oil and 134A - been icy cold ever since.

In this pic you can see how dirty the hose was from the oil and dye that was leaking out:
View attachment 1091516
Going in next week to get her leak tested. Question is, if it holds vacuum, is that an indicator that the system is tight? Or can it still be leaking and hold a 1/2 hour vacuum after disconnection?
 

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Vacuum is not a sure fire way to tell if the system is completely leak free. It will find large leaks but not small ones.

If the system is out of refrigerant, and a service valve is suspected, replace it. A tire valve stem tool should work to change it out before having it vac-n-filled. Have them add dye when before they fill it.
 
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Discussion Starter · #8 ·
Vacuum is not a sure fire way to tell if the system is completely leak free. It will find large leaks but not small ones.

If the system is out of refrigerant, and a service valve is suspected, replace it. A tire valve stem tool should work to change it out before having it vac-n-filled. Have them add dye when before they fill it.
agreed, went through with that in an older car (the car was not old at the time) It is $25.00 to add dye into the system to detect leaks while I am there. But more importantly, it is a way to detect them later on right?
 

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Discussion Starter · #9 ·
Vacuum is not a sure fire way to tell if the system is completely leak free. It will find large leaks but not small ones.

If the system is out of refrigerant, and a service valve is suspected, replace it. A tire valve stem tool should work to change it out before having it vac-n-filled. Have them add dye when before they fill it.
he wants to put some vapor of R134 in to get the system going so he can electronic leak detect the high side ball valve port
 

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he wants to put some vapor of R134 in to get the system going so he can electronic leak detect the high side ball valve port
If you have no refrigerant in there, then he will have to add refrigerant to be able to use that electronic leak detector. Also adding UV dye can be useful to look for leaks later down the line, should another leak occur. Not sure on an LBZ, but an LB7, the high side connection is a complete screw on valve assembly and the low side is a schrader type one. Good luck
 

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Discussion Starter · #11 ·
If you have no refrigerant in there, then he will have to add refrigerant to be able to use that electronic leak detector. Also adding UV dye can be useful to look for leaks later down the line, should another leak occur. Not sure on an LBZ, but an LB7, the high side connection is a complete screw on valve assembly and the low side is a Schrader type one. Good luck
I agree, I am in Canada, so prices are in Canadian $, $75 to do leak detection and charge to the right amount of R134A including trucks, he is a commercial HVAC tech 4 days a week, and does this when he is home, he has a Robin Aire recovery and auto charge system.

I have purchased an OE Low side Schraeder valve from Rock Auto, along with the high side ball valve port which as left uncapped by the previous owner so he said to replace it for sure because it may not seal anymore once he puts the gauges on that port because it was packed full of mud and debris, really badly.

Do you recommend to have him put dye in it from the get go, or as he says let us put a whiff of gas (enough to cycle the compressor) and see where that takes us, great if it is a large leak, and if we cannot find an obvious leak, introduce the dye then?
 

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From how you describe the HVAC tech, go with his recommendations. Sounds like he has all the proper tools and that electronic tester is actually a good method. I used the dye for future leaks because my leak was literally audible, holes in the condenser, when I turned off the truck after I added some refrigerant
 
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