Air Conditioning?


2005 model vehicle , no pressure in ac system , no history on vehicle so don’t know if a small leak over a long period of time or a larger leak . My understanding is most vehicle ac systems leak at least a little & may need topped off occasionally . If a vehicle has a very small leak that lost the refrigerant over a long period of time is it more than likely that enough air entered the system to contaminate the system beyond what a recharge might fix ?
I have a vacuum pump & manifold kit & I know that if I pull a vacuum on the system I will likely pull air into the system even if the leak is tiny . At that point I will at least have to replace the drier .
I also have a case of refrigerant so I can easily sacrifice a can . Would you install a can & see what happens or go ahead & vacuum the system & see if it holds ? This is my vehicle so I’m not doing it for someone else .


2005 . . WHAT ? ? . . model vehicle ?
NO, most a/c systems do not leak a little bit, they are a sealed system.
at 11 years old i’m sure some o-rings have gotten hard with time and temperature.

Put in a leak detector dye and diagnose it completely.
My 92 Explorer leaked out , only during the cold winter months, two years in a row.
When attempting to diag in the summer . . nothin’.
Only during those cold months did we find the dollar o-rings that needed replaced.

I added in an a/c kit to my 79 Chevy pickup in 81.
I have NEVER needed to add freon. . its R12 will still freeze your fingers.
08 Expedition and 06 Escape have never needed freon


2005 Jeep Liberty . I had also thought of adding a can with dye in it but don’t have that at the moment .


I would pull a vacuum on the system, close the manifold valves, turn off the vacuum pump, and see how long it takes for the pressure to bleed down.

That will give you some idea how large the leak is.

The best way to find a leak is, charge the system with nitrogen gas and then take a sniffer and detect for leaks. But if you don’t have this equipment, the only alternative is a can of refrigerant containing a dye.



If it were mine I’d add the can and see what happens. But I wouldn’t get overly optimistic. As others have stated, intact systems don’t leak even a little… and rubber seals get old.

Let us know what you decide or how you make out.


I’m not overly optimistic but you never know . Think I’ll pick up a can with dye , add it & see what happens . I’ll have to find the probable leak if as suspected there is one . Thanks guys , was having a hard time deciding whether to pull the vacuum or go ahead & add a can . I’ll post back later & let you know what I find .


When you say no pressure, do you mean that if you press the schrader valve, there is no residual freon escaping or do you mean that there is not enough pressure for the system to operate? If there is any residual pressure at all, even if it is just a little puff, then there is no air in the system. To draw air in, there would have to be a vacuum at some time, which you could get when the temperatures outside vary during the day and night.


Pressed the schrader valve & nothing .


I’d just throw a can in there. If you attempt to draw a vacuum and there is a big leak, you will draw in a lot of outside air and moisture. Better to keep a positive pressure in the system as much as possible until you determine the source of the leak.

I know this might sound a little odd, but if you have a full gauge set, instead of adding freon in the traditional method, I would leave the engine off, double check the pressure from the high side, then add the freon to the high side with the can upside down so that the pressure in the can forces liquid freon into the high side of the system and let it pressurize backwards, actually following the normal flow of the coolant.