Automotive Air Conditioning Information Forum

This probably a dumb question. There is a gasket on the low side port cap and it does appear to have PAG oil on it. Are you saying it is normal for there to be a slight leak with the valve and the cap is really what seals the system? Sorry I’m so dense.

And if there is a slow leak on the low side Schrader valve, would you try to tighten it first or just buy the tool that allows me to change the Schrader valve without evacuating the system?

Thanks….

case2001 wrote: ↑Sun Mar 26, 2023 1:58 pm Are you saying it is normal for there to be a slight leak with the valve and the cap is really what seals the system?

Yes, what you asked is correct.

case2001 wrote: ↑Sun Mar 26, 2023 1:58 pm And if there is a slow leak on the low side Schrader valve, would you try to tighten it first or just buy the tool that allows me to change the Schrader valve without evacuating the system?

I would make sure that the Schrader valve is snugly screwed down (not over-tightened) inside the test port, which you can do without recovering the system, and that the outer cap is on finger-tight. That should do the trick.

Schraders normally leak a slight bit, as said, so you might notice a little puff of refrigerant the next time you remove the cap. But the o-ring or gasket inside the cap will provide the tight seal against the top of the port, preventing refrigerant loss.

You might prefer not to invest in the tool you mentioned for a one-time use, unless you like cool tools, like I do

Again, thanks so much for the help. It looks like there is Mastercool that will do 134a and 1234yf on Amazon. The one for the 134a only is $68. The one that does both is $160! I think that it might be handy to have. My son and I have been doing this as a learning experience.

I will try to tighten it but if it still leaks might replace it for the practice.

I will report back.

Ok,

The low pressure Schrader was tight. So I loosened a quarter turn and tightened. Replaced cap and came back 30 minutes later. There is still a wisp of refrigerant when I remove the cap.

I can’t believe it because I pressure tested the system with nitrogen at 70 psi for over 24 hours with the caps on. Definitely no leaks.

I think I’m going to go with the Mastercool universal unit. It’s pricy but has excellent reviews and will likely use it again. If I have to refill the system it would be around 75 dollars anyway for Freon.

"There is still a wisp of refrigerant when I remove the cap."
We are trying to tell you that is normal!!!

You can change the schrader all you want it won't make any difference.

We had 14 cars over here last summer for a cookout. I popped the hood on every one and popped off the port caps, and let my sniffer have at it. All but 2 of the 28 schraders showed a slow leak. With the caps on, sniffer picked up nothing.
You don't have to like it, but this is how things are.

You are over-thinking it, my friend

You are not the first one to tell me I’m overthinking it!

Ok. I’ll leave it alone.

But what makes you pull the trigger to replace it? How bad of a leak at the valve would make you replace it?

Thanks again…. My son and I have learned a lot from you guys!!

case2001 wrote: ↑Tue Mar 28, 2023 4:05 pm But what makes you pull the trigger to replace it? How bad of a leak at the valve would make you replace it?

A slight puff of refrigerant as you remove the cap wouldn't be of concern, but a constant hissing of refrigerant from the Schrader valve would require its replacement.

case2001 wrote: ↑Mon Mar 27, 2023 4:33 pm I think I’m going to go with the Mastercool universal unit. It’s pricy but has excellent reviews and will likely use it again. If I have to refill the system it would be around 75 dollars anyway for Freon.

Since this is a learn-as-you-go project for you and your son, I can understand purchasing the Schrader valve tool set.