So my car broke down due to a transmission cooler line leak. Had it towed to a shop where they diagnosed the issue, replaced the cooler lines and at their recommendation replaced the radiator. I pick up the car and after about 15 minutes of driving realize the A/C is just not blowing cold. I call to ask if they would have evacuated the refrigerant to install the new radiator. Guy at the shop says they're 2 separate systems and wouldn't have done that. Suspiciously the schrader valve caps are also missing. I'm not one to argue so I try to diagnose the issue myself. Notice the AC clutch isn't engaging. Hot wire the relay and it clicks. Cross my fingers and hope it's a faulty relay switch. Not the problem. Order a manifold gauge set & the entire system is at zero PSI. So either there's a leak or somebody removed the refrigerant. I pull a vacuum and it maintained at the -30psi for an hour so either it's a really slow leak OR somebody removed the refrigerant, realized they may not have needed to do that, and then forgot to add it back in because well why would the refrigerant be missing. Anyway at this point I might as well finish the job but would greatly appreciate some sanity checks here before I go ahead.
Do I need to add any oil to the system? I have no idea how I'd determine the amount that would need to be added and without a "no you're good" or a "just add x and you'll be good" I'm going to take this into a (different) shop.
I haven't ruled out the possibility of a very slow leak. The transmission cooler lines were leaking and the car is not the newest. I figure adding some UV dye would help catch any leaks and in that case I take it into the shop.
A lot of refrigerant comes with stop leak. I've been seeing mixed opinions online about this stuff and want to get some feedback on whether it's worthwhile to use. My 08 Ford Ranger (4L v6) calls for 2lb 1oz -> .94kg -> 33oz so I need 3 12oz cans. Any reason to make 1 of them a stop leak can? Strong feelings here? Right now I'm defaulting to not using it.
My plan is to pull a vacuum. Add refrigerant to the low side while the car is running w/ Max AC and basically aim for getting 33oz of the theoretical 36 oz I'm purchasing into the system with some UV dye all while trying to maintain the suggested PSI on the r134a refrigerant chart. I've got a kitchen scale to measure the quantity added. I've also read some stuff about making sure the freon doesn't enter the compressor as a liquid. I imagine if I just make sure the low side pressure stays close to 30 I should avoid that issue. Can always adjust how open the low side valve is to slow it down if it's building too fast. From what I'm seeing on the internet at 60 F you need to stay below 57 PSI & 70 F you want to stay below 71 PSI so rule of thumb is keep it below the ambient air temp in F. Anyone here that can speak to this part of the process?
Thanks in advance and apologies for the length.