Author Topic: Winter project 1956 A/C vacuum test ** Update**  (Read 286 times)

Offline JAG56Cad

Winter project 1956 A/C vacuum test ** Update**
« on: February 02, 2019, 10:02:37 AM »
One of my many pet projects for the winter time is to tackle the A/C. After installing the rebuilt dehydrator/receiver I needed to check for leaks especially with all of the multiple connectors around the long lines front and rear.

I’ve been fitting a gremlin slow vacuum leak for several days, after reversing the process and applying pressure air to get to the bottom of my issue.  >:(

Next step close both shut-off valve at the compressor so both lines are now close so only the compressor is connected for the test. Again, both shut-off valve covers were place back and tight.

After applying about 20 psi, I spray some soapy water around the compressor lines and immediately found a leak around both shut-off valve covers. I removed the valve covers and again spray around the valve shafts and found both were leaking.

First thing I’ve notice the valves inside are made of brass so there is not a perfect seal when they are either open or close. Now I’m not sure if there is some type of plastic or rubber inside around the valve shafts to properly seal them. ???

So my first thought was “there should be some type of seal at the cap”. ???

The ’56 Service Manual is of no help since there is no pictures or details on the shut-off valves.   :(  I did some research and found a 55 and 56 Chevrolet Service shop manual for the A/C which does show and explain the function of these valves. These manuals also indicates the shut-off valves have a gaskets on them but they do not show where they are located.

Here are the links for these manuals;

http://chevy.oldcarmanualproject.com/booklets/55top41/index.htm
http://chevy.oldcarmanualproject.com/manuals/55rs36sm/index.html

Further research I found a picture from the 1955 Buick A/C compressor showing the location of the seal or as it was refer on the picture to a “gasket” (see 1955 Buick compressor seal picture).

So I took both the valve caps and the high and low side fitting caps off. Added an “O” ring to the fitting caps as well as to the shut-off threaded end. Just as a precaution, I’ve also add a piece of rubber tube at the valve steam so the cap can compress it as a secondary seal (see 1956 shut-off valve picture).
 
So far the vacuum test is holding steady at 30 Hg for a few hours now, will see if this holds for a few days.

If you are the lucky (or unlucky) owner of a 1955 or 1956 with A/C please make sure you have these seals on the caps. You do not want the expensive R12 to leak out from either side of the valves..!   ;)

Good luck..!
« Last Edit: February 05, 2019, 12:07:29 PM by JAG56Cad »
Jose Gomez
CLC Member #23082

Offline South_paw

Re: Winter project 1956 A/C vacuum test
« Reply #1 on: February 02, 2019, 11:18:53 AM »
Nice post Jose.

I wrestled with these valve gaskets in the past. I bought a A/C o-ring kit that came with about 20 or so o-rings made to handle A/C pressure and temps. Changed them all out, problem solved.   
Lou
1956 Eldorado Biarritz
CLC Member since 2001 (Unlisted in Directory)



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Offline JAG56Cad

Re: Winter project 1956 A/C vacuum test
« Reply #2 on: February 02, 2019, 12:17:56 PM »
Nice post Jose.

I wrestled with these valve gaskets in the past. I bought a A/C o-ring kit that came with about 20 or so o-rings made to handle A/C pressure and temps. Changed them all out, problem solved.

Thanks Lou..!

What got me so (#$%^&) is I had to search around for other GM documentation to find more details on these pieces. Since back then owners were not expected to work on Cadillac’s we now have to search around other GM products and get into our liquor cabinet more often to get things fix.   :D
Jose Gomez
CLC Member #23082

Offline JAG56Cad

Re: Winter project 1956 A/C vacuum test
« Reply #3 on: February 03, 2019, 08:35:37 AM »
Well I had a chance to take a closer look at the valve with my inspection camera and for sure there is a need to seal the area for the valve to properly seal especially around the stem inside the shaft and were the valve seats at the top.   :o

Larry Blanchard suggested using graphite Garlock rope packing - > http://forums.cadillaclasalleclub.org/index.php?topic=153966.0

It sound intriguing and possible a solution..! I have to give it a try and see if it works, more to come.
Jose Gomez
CLC Member #23082

Offline rare eldorado

Re: Winter project 1956 A/C vacuum test
« Reply #4 on: February 03, 2019, 09:27:38 AM »
hello jag 56 I had the same problem with a customers 56 .took the valves too a machine shop and they milled the flat surfaces as to ware they were smooth again It was almost the same as milling a head .This gave a new like finish ware new seals would fit on a new surface .Most hydraulic repair shops can rebuild these valves .If you still have a problem try this alternative.

Offline JAG56Cad

Re: Winter project 1956 A/C vacuum test
« Reply #5 on: February 03, 2019, 10:09:01 AM »
hello jag 56 I had the same problem with a customers 56 .took the valves too a machine shop and they milled the flat surfaces as to ware they were smooth again It was almost the same as milling a head .This gave a new like finish ware new seals would fit on a new surface .Most hydraulic repair shops can rebuild these valves .If you still have a problem try this alternative.

Would you know how they were able to take the valve out?

I check the valve at the stem and there seem to be pressed in ??? and not much space to get the bottom piece out ???

Thanks for the suggestion.
Jose Gomez
CLC Member #23082

Offline caddyguy

Re: Winter project 1956 A/C vacuum test
« Reply #6 on: February 03, 2019, 10:56:54 AM »
Valve stems are a bitch to work on, and unless you have the equipment to the job, your wasting your time. Also when pressure testing a/c line you need to use nitrogen. It is a dry inert gas. Air has moisture int it and the amount depends on humidity in the air. This is what the dehydrator picks up out of the refrigerant. Best to cap off all open lines to limit the moisture entering the system. After making repairs you will need to pull a good vacuum, and change the oil in the vacuum pump. This will help pull down into a deeper vacuum. Good luck. G

Offline JAG56Cad

Re: Winter project 1956 A/C vacuum test ** Update**
« Reply #7 on: February 05, 2019, 12:08:10 PM »
Well latest update.

I’ve try the solution provided in Larry’s post at the CLC board and hope for the best.

Got the 3/32 graphite valve steam packing from the local Lowes. Place small pieces around the shaft trying to cover all areas as much as possible. The lower end was a bit cumbersome but with a small hook I was able to get the bottom pack.

Close the valve and squeezed the extra out, repeated the process and made the final closure of the valve.

I place the valve assembly back without the valve caps and proceed to vacuum the lines. Vacuum was pull at around 28-29 Hg and so far it is holding for roughly 2 hours.   :)

I just place the caps back and will monitor for a few hours more but I think this solution is a winner..!

I do not intent in opening the valves again as they may need to be re-packed after the seal is broken and do not see the need to play with them. As they old said "if it ain't broke, don't fix it"..!  ;)

I do appreciated Greg’s and Larry’s 411 solution, hope this tip will be helpful to other ’55 and ’56 owners.   8)
Jose Gomez
CLC Member #23082