Oh yeah -nothing like a system with sealer! Stuff hardens to concrete when exposed to air, rendering the system useless when the stuff fails to work and they bring it in to get it done right.
Re .... cover ... y machine? What is this foreign language you speak?
I just tried my propane trick on the Marquis. Didn't work as well as it did on the El Camino, although that was a TXV system where the Marquis is FFOT - totally different ways of metering the refrigerant. It was just starting to cool when the pressures started approaching 350 psi ... and in a 28 year old car with original hoses, that's outside my comfort zone, especially with High side temps approaching 250°.
So I'll be removing that, and buying some store-bought propane instead. It's called Envirosafe ...
Far be it from me to buy anything with the words "eco" or "environment" on the label, but propane works. Just gotta get the pressures down. They blend it with butane to achieve that. I still have a 30lb keg of 134a, but the stuff just plain don't work well in a system designed around R12. Damn eco *censored* ruined that whole thing, and cost us consumers BIG in the process. Don't even get me started on that topic!!
As a matter of fact, you can thank the EPA for having to spend thousands on a recovery machine, and for all the voodoo "mechanic in a can" fixes that are out there now.
I still have some cans of Freeze-12 left over from the first charge. That stuff is 80% 134a and 20% 152b to lower pressure and aid in oil flow. Used the stuff in the 'Camino down in Phoenix with excellent results. Turns out, they stopped making the stuff back in '11, and the stuff is selling for nearly $50 a can now! WOOHOO for me! Got a few cans left I can try to pawn which will result in a free A/C recharge. Will even pay for the new accumulator I just bought as well.