High side AC leak

[JHZR2]

I don’t know how long ago the AC was run in my auction win 1991 MB 350sd. Likely years. Put gauges on it, and the pressure was about 7-8 psig.

The high side connector is caked with dirt, which tells me there probably was a slow leak at the 134a adapter.

I would likely revert the car back to r-12 once I know it’s leak tight. Until then, I’m inclined to refill with r-134a, though if I have a suspected leak, I usually use HC with great success.

Given that it is likely years and the car still had a bit of charge, in cold weather, and I have no evidence that there was any barrier hose replacement, what path would you take? I’m thinking to carefully add r-134a to an acceptable pressure and running it for a while, sniffing and watching pressures. Assuming that holds, I can then either have it evacuated and refilled by weight, or more likely, evacuated, then I’ll flush it, change the R/D, and instal r-12 which I have, by weight. Obviously installing r-12 without significant confidence in the system (which I do in other cars that still run r-12).

Thoughts on the grime around the high pressure port? Thinking I should change orings and schrader in advance. What about the r-134a plan?

Thanks!

 

[paulo57509]

I would be weary of the condition of the system; is it just a leak or is there additional work to be done to get it running? At a minumum, I would draw a vacuum (how gross are the leaks), if the leaks are "slow", partially fill the system and sniff them out. Once this assessment is complete, you can then make more informed decisions on how to proceed. I wouldn't convert it until I know the system is sound.

IMO, with AC work there are no shortcuts. Even patching it back together can get expensive really quickly; time and money are better spent just repairing the system properly.

I converted the Lumina to R134a back in 2011 when the system succumbed to "black death" compressor failure. This required removing all the components, flushing the system (lacquer thinner) to remove the mineral oil, black debris and replacing the seals, compressor, orifice tube, receiver/dryer and hoses at the compressor. The Lumina is now falling apart and really needs to be junked. The AC however is still performing like new.

 

[JHZR2]

I would be weary of the condition of the system; is it just a leak or is there additional work to be done to get it running? At a minumum, I would draw a vacuum (how gross are the leaks), if the leaks are "slow", partially fill the system and sniff them out. Once this assessment is complete, you can then make more informed decisions on how to proceed. I wouldn't convert it until I know the system is sound.

IMO, with AC work there are no shortcuts. Even patching it back together can get expensive really quickly; time and money are better spent just repairing the system properly.

I converted the Lumina to R134a back in 2011 when the system succumbed to "black death" compressor failure. This required removing all the components, flushing the system (lacquer thinner) to remove the mineral oil, black debris and replacing the seals, compressor, orifice tube, receiver/dryer and hoses at the compressor. The Lumina is now falling apart and really needs to be junked. The AC however is still performing like new.

Im acutely aware of the situation with old ac systems. I maintain R-12 systems on many old cars. I’ve had to rebuild and change systems before.

R-12 is the best bet for cars meant for it by design. I’ve had decent r134 retrofits but there are many variables.

Right now im just baselining this new to me vehicle so I can see how it performs and make decisions for the long term. Frankly, seeing that much pressure, while leaking slowly, tells me that the system isn’t that bad. I can’t vent the remaining r134, and I don’t have bone dry nitrogen. But I do need to do diagnosis, and I have no way to tell how slow or fast any leak is. But I suspect it’s very slow based upon the cars history. So it’s really a matter of $9 in HC or $13 in r134a.

 

[Fitter30]

R 12 system uses mineral oil R134a uses polyolester oil (POE). Using nitrogen would be the best choice after repairs for leaks. It's doesn't change pressure with temperature that much. Before and after a evac with a micron gage just to remove any refrigerant that might have migrated into the oil. Might want to replace the expansion devise and drier also after the leaks are repaired.

 

[JHZR2]

R 12 system uses mineral oil R134a uses polyolester oil (POE). Using nitrogen would be the best choice after repairs for leaks. It's doesn't change pressure with temperature that much. Before and after a evac with a micron gage just to remove any refrigerant that might have migrated into the oil. Might want to replace the expansion devise and drier also after the leaks are repaired.

Yes, I’m aware of the oil differences. Keep in mind I’m not yet doing an R-12 convert-back. That would require a decent disassembly of the system, flushing, etc.

Definitely in the cards.

For now, I’m just baselining the car and making it useful as part of my collection. That means understanding the AC system status, and what is or isn’t good with it. Evaporator is my biggest fear, but it seems that since the system still had marginal pressure, that the evaporator isn’t leaking.

Beyond that, it’s a matter of having a working ac so I can start to use the car a bit.