thanks very much, paul and steve.
I have an old vacuum pump, but it'll 'pull' only 27 lbs max vacuum. still short the gauges, but the vac pump has an old vacuum gauge (from a car tester) hooked to it with a sort of two-valved manifold 'of sorts'.
I'm wondering if I could judge how bad a leak I might have by hooking it up, pulling it down, isolating just the gauge to the car AC system, and seeing how long the vacuum -does- last. how long 'should' it last? minutes? days?
is 27 lbs of vacuum 'enough'? or does the factory recommend 30 lbs?
also, say I pull a 27 vacuum on the system: at what 'rate of leakback to ambient' is a 'fix your leak first -prior- to recharging' situation adviseable? for practical purposes, is there a rate of leakback to zero vacuum over time 'acceptable', generally speaking? please describe?
so, you're saying 134a is available 'over the counter' in most auto parts stores?
on a related note: don't most car AC systems 'leak down' over time? the car was new in 1999, so it's been, uh, 4 yrs. isn't having to recharge from time to time 'normal'? how long does a 'typical' system refrigerant charge (if there is such a thing) _last_?
is there any practical way for a guy to determine IF the front compressor seal is bad short of either dismantling the compresssor OR using a (very expensive) sniffer device? guess I'm asking how an old 'po boy' might isolate a leak to a known spot (seal? hose fitting? maybe?) 'short of' having a sniffer -is- there a way?
in any event, once the system is 'opened to atmosphere', is a new receiver-dryers recommended? (thirty yrs ago, that's what they were called - maybe they're called something else now?)
again, thanks much, for educating me