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low side port cap misssing.. r134 is now all gone

jdc25180 on Wed April 07, 2010 11:09 PM User is offline

Year: 2001
Make: lexus
Model: is300
Engine Size: 3.0
Refrigerant Type: r134
Ambient Temp: 75
Pressure Low: 0
Pressure High: 0

I took my car to jiffy lube to get topped off as it only got cool after getting to highway speeds. That didnt make a difference after it got topped off. The wife it to work the next day and said that it didnt work at all now. In preparing to hook up my manifold gauges I saw they left the cap off of the low side port. Correct me if I'm wrong, but doesnt the low side create a vacuum and it will pull the needle valve open and release all the r134?

mk378 on Wed April 07, 2010 11:57 PM User is offline

Leaving the cap off should not cause the pressure to go to zero in two days. Your vacuum theory is not true. If a negative pressure did occur (which generally doesn't happen in normal operation) it could draw air in, but would not let refrigerant out. So I suspect there is a more major leak somewhere else.

HECAT on Thu April 08, 2010 7:13 AM User is offline

Leaving the cap off for a few days should not do it; but if the service valve did not reseat properly and the cap (primary seal) was left off, well maybe.

If charge is gone (you did not say if you confirmed with your gauges, a static charge or empty), change dryer, evacuate, and recharge with factory specified weight; and test for leaks. IMHO, do this yourself, or drive by "iffy lube" to go see a Pro.

If it was low, and if "iffy lube" added anything, and it still did not cool at slow speeds; I would look for restrictions (dirt, bugs, etc) or problems (shrouds, seals, fans, etc) that would limit proper air flow over the condenser.


HECAT: You support the Forum when you consider for your a/c parts.


k5guy on Thu April 08, 2010 11:24 AM User is offline

I agree with other posters. Due to the design of the service ports, it is highly unlikely. When the system is pressurized and the service port leaks, the pressure inside usually forces the service port valve to seal. I do think the cap on the service port being missing shows sloppy work and poor quality control. Just like a tire valve, it isn't entirely necessary, but it keeps the valve clean of road crud. I would either have a chat with the service manager (or owner) or take it somewhere that knows what they are doing and take pride in what they do.

Another option is to learn how to do it yourself. Buy a set of real gauges, and check the pressures.


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jdc25180 on Thu April 08, 2010 6:24 PM User is offline

Before I took it in, the compressor was turning fine, clutch engaged no problem. "iffy lube" said it was a half pound low and evacuated everything and filled it back up. Even toppped off, it only cooled at highway speeds, or if you revved the engine above 2500 rpm in park. I knew I was in trouble when I saw the tech aka shop manager spray pb blaster on the compressor clutch. I asked why he was putting pb blaster on my clutch when its working fine. He didnt give me a answer. With the ac button on, the clutch engaged and compressor turned, when the ac button was off the clutch was disengaged and the compressor stopped turning. I could see it if the clutch clearances were off and it was rubbing and making noise.. but there was none. There isn't much more to it.

Also I did verify that there is no r134. I knew there was a problem, when the clutch quit engaging altogether after the wife brought it home after she got off work. I went and bought some gauges and hooked it up and there was nothing. Not even pssssssssst when hooking up to the service ports. I can push the needle down on the high side with a punch and nothing. So I know the pressure switch is working...

So now I think I'm done altogther with iffy lube. Though googling around I've come to the conclusion that I probably have a worn compressor at 120k miles and only cooling at high rpm's.... parked or at 70mph. $500 for a compressor and $50 for a dryer and some ac flush and a vacuum pump should get the wife a cool car.

thanks for everyones help

mk378 on Thu April 08, 2010 10:24 PM User is offline

Sitting at zero pressure now, charge a small amount of R-134a for a leak test. Do not run the A/C; just open the valve and bring the static pressure up to 40 or 50 psi. This will only take a couple oz of refrigerant. Leave the gauges attached wait a few hours to see if pressure decreases because it leaks out. If it does, you know there's a leak somewhere other than the shrader valves.

Edited: Thu April 08, 2010 at 10:25 PM by mk378

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