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Barrier Hose on old R12 fittings

Old Goat on Mon July 09, 2012 10:51 AM User is offlineView users profile

Year: 1967
Make: Pontiac
Model: GTO
Engine Size: 6.6L
Refrigerant Type: R12
Country of Origin: United States

Just about to charge system with R12 when I happened to look at this thread.

Barrier Hose

I have totally rebuilt the whole system, including the A6 compressor and have vacuumed it down to 29.5 inches of vacuum. It is holding it for two days now and I am wondering if the barrier hoses that I put on there with aero seal clamps will leak after charge up, even if they are holding vacuum really well???

Sure would like an opinion by someone knowledgeable ASAP. Was wanting to drive cool, but don't want to waste my R12 stock!


Leggie on Wed July 11, 2012 9:35 PM User is offline

Just because it holds 15psi outside-in doesn't mean it will hold 250 psi inside-out.

Disable the compressor clutch, pressurize to atmosphere with R22 or 134a and pressurize the entire system to 175 psi. Check every fitting with a sniffer.
Then, drive around and get it steamin' hot. Test again.

Do not use shop air as since its not dry like dry nitrogen.

When I say "pressurize to atmosphere, you only add enough R134a(you can use R12 as well.. if you want to waste it) so system is no longer at vacuum. This is called a tracer charge. The allows the detector to pickup and nitrogen top charge add enough pressure to the system to simulate actual working conditions.

Pressuring to 175 psi does not harm the low side. The saturation temperature of refrigeration is determined by the coldest spot in the refrigeration charged circuit and 175 psi is the pressure of R12 at 130F. When you let a car heat soak in sun all day, the whole system becomes 130F+

When its done, you may vent the charge into the air. When its used as a tracer charge, its not considered refrigerant by EPA regs.
Keep in mind that barbed fittings may not hold after repeated heat cycles.

Edited: Wed July 11, 2012 at 9:37 PM by Leggie

Dougflas on Wed July 11, 2012 9:54 PM User is offline

Do not put R22 into this system, The R22 will permiate the hoses.

Leggie on Wed July 11, 2012 11:27 PM User is offline

You don't use R22 to keep inside. You only use a trace amount so leak detector can pickup.

bohica2xo on Wed July 11, 2012 11:43 PM User is offline

That system will leak R22 like a sieve. Don't use R22 for testing.

Adding a couple of ounces of R12 for the sniffer is one way. If you don't have a sniffer, pressurize it with dry nitrogen & wait a few days before checking the pressure for leakdown.

Why are you unsure of the barrier hose joints? Were any of the OEM fittings really rough? If you are holding vacuum for days, and have used a good clamp then you should be ok. I would re-torque the clamps before charging.


"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

Old Goat on Fri July 13, 2012 8:05 AM User is offlineView users profile

I called the the folks where I got the barrier hose from and they said "no problem, we use it all the time on those systems with R12 and do not have any trouble". So, I charged it and all is well. 37° out of the vents.

Thanks for your help.



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