Troubleshooting AC leak before charging with R134a

[1991 Corvette ZR-1]

Originally Posted by Jagdpanzer

Dorman has a brass cap for this purpose.
https://www.dormanproducts.com/p-80262-902-025.aspx


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Thank you for this. I ordered it and should have same day as the schrader valve removal / installation tools. I will coat the threads with some type of sealant, thread it in the R134a adapter and do another vacuum check once I have it.

[XfireZ51]

Originally Posted by 1991 Corvette ZR-1

Thank you for this. I ordered it and should have same day as the schrader valve removal / installation tools. I will coat the threads with some type of sealant, thread it in the R134a adapter and do another vacuum check once I have it.

That was going to be my question regarding the 134a adapter. What sealer are u using for the adapter to the high side port?

[1991 Corvette ZR-1]

Originally Posted by XfireZ51

That was going to be my question regarding the 134a adapter. What sealer are u using for the adapter to the high side port?

I will be using Nylog Blue gasket and thread sealant. It is formulated to work with AC systems and will not contaminate the system. I used it on the new O rings I installed throughout the system.

[ghlkal]

Good, informative thread.

Thanks for documenting your work 1991.

I too had a leak via the high side schrader valve, and it took several different valve stems before it was fixed. (Hopefully it's still holding this year ...)

[XfireZ51]

I?m picking up the Dorman Zbrass fitting tomorrow from AZ.
Is it possible to check if system holds vacuum without connecting to high side valve fitting?

[1991 Corvette ZR-1]

Originally Posted by ghlkal

Good, informative thread.

Thanks for documenting your work 1991.

I too had a leak via the high side schrader valve, and it took several different valve stems before it was fixed. (Hopefully it's still holding this year ...)

Thanks! Hopefully it helps someone else out.

Originally Posted by XfireZ51

I?m picking up the Dorman Zbrass fitting tomorrow from AZ.
Is it possible to check if system holds vacuum without connecting to high side valve fitting?

I?m not an expert but the system as a whole is circular, so I will say yes. As my high side valve is suspect, I have been using the low side off the accumulator to vacuum test. If you get some various sized rubber stoppers from Lowes or the hardware store that are conical shaped, you can use those to plug the ends of hoses, ports in various parts so you can pull vacuum.

Right now I have vacuum on the whole system, minus the hard line which is on the garage floor. I just removed the orifice tube from the evaporator line and plugged it. I then plugged the opening of the condenser connection for the high side and then I pulled vacuum off the accumulator and letting it sit.

Doing this to make sure everything is playing nice now that I have tested all of the parts separately. Excessive, but I?m also the paranoid type when it comes to this kind of stuff.

[1991 Corvette ZR-1]

Installed the Dorman AC schrader plug and put a vacuum on the hard line while it?s on the garage floor. -30 inHg for about eight hours so I think we are good! My schrader valve removal tools show up tomorrow, so I think I am going to attempt to remove and replace the valve before I cap it and install back in the system.

If someone has the part for the valve core let me know. Otherwise, I think the larger of these valves will be the one I need to install.

[XfireZ51]

Originally Posted by 1991 Corvette ZR-1

Installed the Dorman AC schrader plug and put a vacuum on the hard line while it?s on the garage floor. -30 inHg for about eight hours so I think we are good! My schrader valve removal tools show up tomorrow, so I think I am going to attempt to remove and replace the valve before I cap it and install back in the system.

If someone has the part for the valve core let me know. Otherwise, I think the larger of these valves will be the one I need to install.

I was only able to find tire valves for Schraders. Is the AC valve different from the tire valves?

[1991 Corvette ZR-1]

Originally Posted by XfireZ51

I was only able to find tire valves for Schraders. Is the AC valve different from the tire valves?

The valve cores appear to be different. The high side is a different size from the cores used for the pressure switches on the same hard line. I got a small assortment of valve cores to try. The factory high side core is on the left, the new one on the right. It wasn?t a perfect fit as the top was slightly larger than the opening to fit inside and screw in. So I filed it down slightly and it worked. It appears to seal when vacuum checking it but I may cave and seek a direct replacement that represents the original factory core or as close to it as possible.

I goofed on my vacuum testing of the hard line. I had the valve closed on the AC gauge while testing, so I only proved the gauge does not leak. So after replacing all the valve cores in this hard line, I still have a very slow leak. Next step after removing the pressure switches is submerging it in water and applying compressed air to it and watch for bubbles.

[1991 Corvette ZR-1]

Just a quick follow up the previous valve core replacement for the high side does NOT work. It is too tall and with gauge on it fully depressed it actually does not allow flow, which I never thought I would have to imagine that kind of scenario. I had to source a new valve core and it is Napa part number 209586. Exact replica for the old unit. About $4 for it and it seals nicely. It?s almost weird to have a high side valve that does NOT leak.

All of my valve cores leaked on the high pressure hard line. I will say this, this is a high mileage ZR-1, but by the time I go through every damn component on it, I will have restored some of the low mileage youth. Short of the engine internals, there isn?t anything I haven?t touched or serviced on this car.