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Is it ok to leave the a/c system under vacuum for a day or two?

Started by chrisntam, May 20, 2018, 10:17:34 PM

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chrisntam

Got the compressor replaced, put oil in the sump (based on what was removed & per FSM), hung the drier and put it on the vacuum pump for about 1.5 hours.  It drew down to about 29.  Closed the gauge valves and it's holding steady.

I'm tired and will put the Freon in in a day or two.

Is that ok?

I know, it's a little late now, but I can't imagine it would be a problem.  If anything, I'm checking for leaks longer.

With that said, should I turn the vac pump back on for a bit longer prior to loading the Freon in?

I'll keep hand turning over the clutch plate to move the oil around....

chris.
1970 Deville Convertible 
Dallas, Texas

Scot Minesinger

I always do that after major surgery on ac system, and have used same good quality pump for years now, probably over 100 times for 24 hours on a single system.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

chrisntam

You leave the vacuum pump on for 24 hours?  Or let it sit at -29 with the pump off?

Pump is currently off....
1970 Deville Convertible 
Dallas, Texas

"Cadillac Kid" Greg Surfas 15364

Chris,
The shaft seal is intended to hold pressure. Assuming you have primed the oil pump and lubrcated the seal, to leave the system under vacuum, again assuming there are no leaks elsewhere might tend to suck the lube off the seal leaving it dry when you start it up.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

chrisntam

After sitting overnight (about 11 hours) the low side gauge went from 29 1/2 to about 28 3/4.  Hoping the loss is at the gauges or gauge connections.

I'll charge it up and check for leaks.
1970 Deville Convertible 
Dallas, Texas

Scot Minesinger

I do not leave the vacuum pump connected to the ac system if it is not running.  However, I may let it vacuum for 24 hours if I did major surgery, such as replace compressor, hoses, and etc.  You cannot have too much vacuum and too little moisture in the system.  BTW that small of a vacuum change could be related to a change in temperature or a slight leak in pump seal on vacuum pump.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

chrisntam

Charged it up this morning (I would have rather been watching Perry Mason on METV), took it for a test drive, at it's coldest, it was blowing about 40 degrees out the vents (when on max/recirculate).  About 78 degrees outside.  When on auto, it seemed to be a bit warmer.  I was expecting it to be a lot colder.  We'll see how it goes.

Have to go to work now.   >:(

Thanks for the input, it is appreciated!

chris.
1970 Deville Convertible 
Dallas, Texas

"Cadillac Kid" Greg Surfas 15364

Chris
38 degrees is as low as your system is supposed to get under your conditions. Is the site glass full and are you still using R12?
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

chrisntam

1970 Deville Convertible 
Dallas, Texas

"Cadillac Kid" Greg Surfas 15364

Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-