What I'm about to write may also apply to anyone who comes across this thread:
http://www.pontiacbonnevilleclub.com/fo ... t=actuator
So anyway thanks to HurstGN's suggestion--and a 20% off at Harbor Freight coupon I found on this site--I picked myself up the AC manifold gauge set over the weekend.
Sunday night: checked the 2004's pressures: 30psi low side / 100 psi high side...definitely low.
(Just to check my measurement technique, I checked the 1998's pressures: 45 psi / 200 psi, right smack-dab OK in the very middle of the FSM's diagram of AC pressures)
Sent the wife out to the auto parts store for a 14oz can of direct-charge R134a/PAG (about $17). Filled it in the low-pressure side while watching the high-side gauge. Pushed up to 225 or so psi almost immediately--then within seconds starting dropping...dropping; within 30 seconds high-pressure side was back down to 100 psi. Definitely a bad leak somewhere.
(On the good side, it still would hold
some pressure...)
While she was in the driver's seat, she reported that the AC vent blew cold while the pressure was briefly high...and that she smelled a definite "chemically"/"anti-freezy" smell (probably PAG oil) while the pressure dropped off/freon leaked. Combine that with the fact that I could find no oily traces at any other potential leak points (hoses, lines, ports, connections, condenser, compressor), and I'm 99% sure the leak is somewhere in the evaporator.
Well, now I knew where the leak was, I didn't feel the need for a dye kit or to borrow a freon sniffer. I was either going to seal this baby with some magic-in-a-can, or get ready to rip the whole f**kin' system out.
So after a lot of net-research into sealers, last night (Tuesday) I ran down to the auto parts store and got Interdynamics Super Seal MRL-3 (cost about $23):
http://www.interdynamics-europe.co.uk/r ... .php?id=59
(Note that this is available in the US now, though not yet on their US site)
I got this for two reasons:
1) It is the only easily-available DIY product I could find that has sealers for
both rubber (hoses, o-rings)
and metal (lines, condenser, evaporator) in a single can.
2) It came with the can-tapper service port hose (would have been $13 alone) that allows me to use the cheap $8 cans of freon.
Apparently it seals metal by circulating some sort of moisture-cure epoxy that fills gaps at leak points where condensation occurs. Sounds good to me.
So I warmed up the car with AC on full, shot the Super Seal in, followed immediately by an 11-oz can of plain R134a, and let run for 15 minutes to circulate (as per directions). Pressures now at 45 psi / 200 psi, with both driver's and passenger's AC vents at ~52°F
I shut 'er down, let it sit for 2 hours, and ran it again--pressures still at 45 / 200.
Tested it again this morning, still holding at 45 / 200.
We'll see how long that holds up!