R12vs R134 Slow leak

[charlie1]

We had a Pontiac where we had to add a can of R12 every year for many years. It was converted to R134 about 5 years ago. We have never added a can of R134 since the conversion. Could it be that R134 does not lead as easily as R12??? Or the old leak may have been at the Schrader valves that were replaced with R134 adapters.

Any thoughts appreciated.

[Guest Mc_Reatta]

R134a has a smaller molecular size than R 12 so it will leak more readily.

The Schrader valves aren't replaced normally during a conversion they just have adapters screwed over top of them.

So whoever did your conversion either found a leak and repaired, or inadvertently fixed the leak while opening the system to flush and replace components and replacing the associated o-rings when reassembling.

[padgett]

May have also added the caps to the adapters, my understanding is that the schraders do not always seal well and the cap is expected to do the real job.

That said, for $18 I just ordered a set of replacement schraders from Amaon. Have experienced two in the last two weeks that did not seal properly.

[Labrat]

I'm seeing replacement 134 for sale with a leak sealer in the can lately. Maybe that did it????

[Guest Richard D]

Maybe, but everyone I have talked to said to stay away from leak sealers. Even the two part type.

[handmedownreatta]

Maybe, but everyone I have talked to said to stay away from leak sealers. Even the two part type.

i hope they are wrong because ive used several cans.

[padgett]

Guess I am strange. I prefer to find the leak and fix it. Also prefer to avoid gasket sealers (except for maybe a drop at joints) and spend the time (which not everyone has) to prepare the surfaces. I do tend to grease gaskets before installation (have a good friend who always puts them on dry).

Besides I have never seen (doesn''t mean some do not work, just have no experiance) a stop-gap like a sealer work for long and have heard professionals with reclaimers curse them. I have a friend with one and do not want to make him mad.

My concern would be clogging the oriface tube which is tiny (but has a big pressure drop to help keep clear). Since most of these react to oxygen, what happens when a line breaks ?

Do have the advantage of being able to take three days to replace a compressor including 12 hours of sitting to make sure a vacuum holds.

Wish we had a cheap way to pressure test the system (nitrogen maybe ?) without potentially contaminating it. Any suggestions ?

[Guest Recian]

Im trying to convert mine but the high side shchrader valve is leaking. I have another from a junkyard car but that car had NO refrigerant in it, so idk if that was leaking or not. It's bigger than a regular tire valve like is found in the low side and all R134 valves. Are these bigger schrader valves available anywhere? just curious

[padgett]

See post #4. A set of replacement schrader inserts was $18 and change. Already used one in a high side replacement.

BTW is 50 cents higher now, sometimes I think Amazon prices on demand.

[Guest Mc_Reatta]

Recian, spring for some new Schrader valves. You can pick up at most FLAPS or order like Padgett did.

Padgett, HVAC pros use hospital grade dry nitrogen, available at most welding supply /compressed gas suppliers, to check systems for leaks.

Pretty inert so won't react with the oils, etc. and won't add water vapor.

Charge system to ~ 150 psi and check for leaks.

Since there is no sniffer for nitrogen, they listen for leaks and use soap solution and look for bubbles. If there are areas that are not easy to see, like the evaporator coil, not very effective though.

That's why most auto AC shops use a small charge of R 134 and a sniffer to find leaks or a dye charge and a UV light. Sniffer of course has the advantage of finding leaks in areas that you can't see well or not at all to observe bubbles or dye traces. Forget what they are supposed to use for a system that is staying R12, but there is a blend that EPA will allow to test for leaks in those systems that will set off the standard snifter .