A/C too leaky?

Camry 2004, about 135K miles.

Friday afternoon, temperature maybe 95+, the A/C felt like it was weakening. I was close to my Trusted Independent Mechanic, so I stopped in without consulting Car Talk.

The shop added 0.25 lb of refrigerant (one hour turn-around!), and A/C seemed OK. (Have not driven the car since late Friday afternoon. It’s now Sunday afternoon.)

Checking my records, just two years ago that shop added 0.5 lb of refrigerant. Both then and now, the work order says they added dye to the system, so I infer that they found no detectable leaks.

Question: Is that leakage – 0.25 lb in two years – reasonable for the car?

Tutorial question: I have vague recollection that the A/C works pretty OK as it loses a little refrigerant, but then goes “off a cliff”. Is that right?

The A/C has a leak and the usual suspect is the compressor shaft seal.

Dye checking is not my preferred method of finding refrigerant leaks. The use of dye means that the system needs to be in operation for a while before traces of dye can be noticed. Sometimes there are areas that are not readily visible which may make seeing dye difficult if not impossible.
I prefer the use of an electronic sniffer. Maybe you need to find a shop that uses one of those.

Yes an A/C can appear to go off a cliff at some point when enough refrigerant is lost. The car is 16 years old so leaks are to be expected.

Ideally, an AC system shouldn’t leak any refrigerant. But a 1/4 lb loss over two years isn’t that bad,

Adding a dye does help locate leaks. But if the evaporator is leaking that’s pretty hard to detect. That’s why I use refrigerant sniffer. These can detect leaks as small as 1 oz per year.

If the AC system loses enough refrigerant, the low pressure switch opens and prevents the compressor from operating. So yeah, it goes off the cliff and stops working.