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Redoing the 65 engine compartment and discovered I had no R12 left in the AC system. Part of chasing down the leak is I can test the condensor now that it's nearly ready to lift out. I can pressure it up to test for leaks once its out but I don't know how much pressure it normally operates on. Does anyone know?
 

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I talked to my AC guy just last week about "bench testing" the system for leaks. He suggested 150psi. I'm sticking with ~100 so I don't have to make any adjustments on my compressor.

Condensers are on the high side. My high side was pressured up to 250 during charging and troubleshooting. I'm not advocating that, just saying a good, new system can handle that. An R12 system should CERTAINLY be able to withstand 100psi during a bubble leak check.
 

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R134a systems can operate in the vicinity of 300 psi on the high side where the condenser is located.
 

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Discussion Starter #5
R134a systems can operate in the vicinity of 300 psi on the high side where the condenser is located.
My compressor only goes to 140 so I guess I have to hope if it is leak free at 140 it should be leak free at 250 to 275. I'll find out.
 

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Vacuum will tell you if you have a leak but it won't help you locate it. Our shop uses nitrogen and we sometimes pressurize the system to 300 psi. You can often hear the leak at that pressure. Nitrogen is dry and doesn't add moisture to the system.
 

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Could someone measure the size of the condenser on a 65 66? Width and height? Thanks
 

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A/C systems are leak tested by putting under VACUUM.
I never understood that. I'm not arguing it, I'm just saying it makes no sense. In essence, you're pushing INTO the system at ~15psi/30" Hg max and checking for pressure increase inside of the hoses. Why not push OUT of the system, measuring pressure drop AND do a bubble leak check? ...and do it at much higher pressure?

When I was evacuating my system, I saw that my shroeder valves were sucking in, making it look like I had a system leak. Pressurizing the system put pressure on the internal side of the valve, and they didn't show leakage. (I could sense the leakage under vacuum because the valve cylinder would form a hickey on my finger tip. Under pressure, a bubble leak check works.)
 

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In my experience, they test the system with vacuum, as it doesn't add contamination to the system. They find leaks with nitrogen, as its clean, dry, stable etc..... I would NEVER used compressed air from a normal, at home air compressor. Adding moisture and oil to the system isn't a good thing.
 
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Did you guys that are screaming vacuum even read the OP's post?

"I can pressure it up to test for leaks once its out "

He clearly states that he is going to pressure it up once it's out of the car. I'm not the sharpest knife in the drawer but I don't see how he can possibly contaminate the system if the condenser is completely out of the car unless his hoses are an extra 10' long.
 

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Did you guys that are screaming vacuum even read the OP's post?

"I can pressure it up to test for leaks once its out "

He clearly states that he is going to pressure it up once it's out of the car. I'm not the sharpest knife in the drawer but I don't see how he can possibly contaminate the system if the condenser is completely out of the car unless his hoses are an extra 10' long.
Well, the condenser is part of the system.... unless he doesn't plan on adding it back in.... if thats the case, why test it?
 

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A/C systems are leak tested by putting under VACUUM.
yep, use vacuum to test the system.

Vacuum will tell you if you have a leak but it won't help you locate it. Our shop uses nitrogen and we sometimes pressurize the system to 300 psi. You can often hear the leak at that pressure. Nitrogen is dry and doesn't add moisture to the system.
actually the best way to find leaks is to use a dye in the refrigerant. that will show up right where the leak is.

I never understood that. I'm not arguing it, I'm just saying it makes no sense. In essence, you're pushing INTO the system at ~15psi/30" Hg max and checking for pressure increase inside of the hoses. Why not push OUT of the system, measuring pressure drop AND do a bubble leak check? ...and do it at much higher pressure?

When I was evacuating my system, I saw that my shroeder valves were sucking in, making it look like I had a system leak. Pressurizing the system put pressure on the internal side of the valve, and they didn't show leakage. (I could sense the leakage under vacuum because the valve cylinder would form a hickey on my finger tip. Under pressure, a bubble leak check works.)
vacuum is used because nature abhors a vacuum. also two things happen when you draw a vacuum on the system, one is it evacuates the system of everything, including water. you can tell how much water is in the system by feeling the receiver/dryer while pulling a vacuum and noting how cold it is. i have seen some get really frosty indicating a huge amount of moisture in the system.

second when you stop putting the vacuum t the system, the gauges will tell you if you have a leak or not by either holding the vacuum or dropping to zero vacuum over time. if your schrader valves were letting air in, then they were indeed leaking.
 

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...also two things happen when you draw a vacuum on the system, one is it evacuates the system of everything, including water...

...second when you stop putting the vacuum t the system, the gauges will tell you if you have a leak or not by either holding the vacuum or dropping to zero vacuum over time.

if your schrader valves were letting air in, then they were indeed leaking.
No problem with evacuation. I get it, it's necessary to properly charge the system, but I'm unconvinced that evacuation is necessary to check for leaks. All that is needed is a pressure differential and a verification that the differential doesn't change. Change = leak. To a hose or a connection, by design, the pressure is inside the hose trying to get out, which is counter-intuitive to checking the connection with vacuum (that is, pressure outside of the hose trying to get in.)

Not to be argumentative, I'm just trying to understand: how can a shrader valve leaking when under vacuum be proof that it's a leaky valve under pressure? The coil spring only works by pushing the valve stem OUT. If it were some sort of "leaf spring"-like device, I can see it working in both directions, but not a coil spring. The vacuum inside of those hose is sucking the valve stem inside, against the (weak) resistance of the spring. Under operating conditions, the pressure inside of the hose is pushing the valve stem out and against the o-ring, increasing the leak resistance as pressure increases until the o-ring gets damaged. The coil spring has no function when there is pressure inside of the hose, right?
 

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...actually the best way to find leaks is to use a dye in the refrigerant. that will show up right where the leak is...
When a car comes without freon and no evidence of dye we test with nitrogen before we charge the system. We always add dye to systems we recharge. The machine we use for charging connects both high and low side for the evacuation and vacuum leak check. The shrader valves don't have to hold the vacuum alone. We usually select a 10 minute leak check after evacuation.
 

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@DustyB Realistically, how many times can dye be used for leak checking? I've been reluctant to use it, figuring that I have basically one chance with it. If I have a leak, then won't it stain the leak and make it impossible to determine if the leak got sealed afteward? I thought that it was really hard to fully clean the dye off.

Thoughts appreciated.
 

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@DustyB Realistically, how many times can dye be used for leak checking? I've been reluctant to use it, figuring that I have basically one chance with it. If I have a leak, then won't it stain the leak and make it impossible to determine if the leak got sealed afteward? I thought that it was really hard to fully clean the dye off.

Thoughts appreciated.
Not sure about that. It mixes with the oil so I assume it easily wipes off. Sure stains your fingers.
 
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