66 big block air

[Tony S.]

I have a 66 big block w/ air, I am having a hard time getting it to pull a vaccum, we have rebuilt the STV valve but it sounds like it is still leaking, I have seen a valve to replace the STV and do away with it, have anyone ever used on or have any ideals about how to fix the problem to be able to get it to suck down and hold
thanks
TRS

[Larry M.]

Re: 66 big block air

Tony:

A couple of thoughts:

1. Are you certain that it is the STV? Perhaps you can test off the vehicle to be certain. These are rebuildable and also are $$$$ to buy new (or rebuilt). If you cannot fix, I would send it to Old Air Products in Ft. Worth and have them rebuild and test.

2. Consider getting some end caps for where the STV fit (perhaps even some tight fitting rubber stoppers) and plug the two ends and then try to pull a vacuum. You may have other problems such as split in hose, compressor seal leak, or a bad/damaged o-ring, etc.

3. Another option is to put a small amount of R12 or use some R22 (keep pressure in 40-50 psig range) and then go over the entire system with a refrigerant leak detector. I just did this for a guy in the Louisiana Chapter, and we found one of the original hoses had a crack in it. It also would not hold a vacuum. Auto refrigerant shops and home AC technicians have this tool....perhaps you can borrow or rent.

4. You can also use dry nitrogen (if available) and pressure system to 50 psig or so and use a refrigerant soap solution to "soap" all the fittings etc. If you don't have dry nitrogen, you can use some 134a or Freeze 12.....but then be sure to remove it completely from the system later.

5. The STV replacement pieces that are advertised and sold will work, but your system was not designed for them and they are not optimum. Replacing the STV with a POA is probably a better solution, but is a bit messy/difficult if the AC system is otherwise complete. I do not think the POA will just "drop in", but may require different end fittings or different size end connections. Someone else who has tired this may know exactly how it will or will not work out.

Let me know if additional help needed.

Larry