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Replacing A/C Expansion Valve

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CamJam View Drop Down
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    Posted: Apr/30/2017 at 10:21pm

Looking for some a/c advice from some of the experts here (are you there Ross Peterson?)

Though I bought a new expansion valve, I chickened out and didn't replace it when I restored my car. I remember that it was taking a lot of force to loosen the fittings and I was afraid of breaking the line to the evaporator.  

Now, however, I've blown the front seal on my York compressor for the second time, and I'm wondering if the old evaporator might be part of the problem, so I'm thinking of tackling the job.  Of course, it will be doubly hard now that it's under the dash instead of on the bench.

Anyone have any tricks for loosening those fittings without bending/breaking the copper tubing?  I do have a can of Freeze-It and wondered if spraying the fittings down with cold followed by a heat gun might help break things loose.  Any ideas much appreciated.  As you know, the working space under the dash is very limited.

Thanks!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pdok Quote  Post ReplyReply Direct Link To This Post Posted: May/01/2017 at 9:12pm
I have the same concern with mine.  Started to remove, realized it would take way too much force and stopped.

I'm planning to reattack when I get my hoses remade.  I've read some tips, and I think heat is the trick to use.  Back up the area with thick leather gloves and don't go crazy with the heat gun, is my plan.  Low-Med heat for a while to soften things up.  I don't think the cold will do anything, since the part you want to shrink would be the inner nut.  Although the copper will conduct heat very quickly, I'm sort of thinking that the outer nut would be the one to heat up the most, then maybe the inner nut wouldn't expand as much.

The other thing is to use really good quality flare wrenches.  The cheaper ones will bend a little, opening the jaws just enough to round off a nut.  Usually the smaller sizes do it the worst. Watched a mechanic friend demonstrate with a craftsman vs snap-on, craftsman couldn't hold up.

That said, no reason to think the evap is causing you a problem, and changing the expansion valve really isn't a deal-killer even if you switch to 134. The new one should have 134 in it, which should make it a little more accurate if you're running 134. I've never switched, mostly because I hadn't needed to change the compressor until my 4.0 head swap.  If you switch, you need to replace the receiver/drier (or have the guts swapped), purge the old oil, etc.  Good time to purge the evap is when you've got the expansion valve removed, but unless there was particulate contamination, doubt that's even necessary.

For the york, was it a knockoff or a real original/CCI?  The seal may not have been installed properly, or a substandard part was used.  The seals are fairly straightforward to replace.  Search "York Service Manual PDF" and you'll get this link:



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Post Options Post Options   Thanks (0) Thanks(0)   Quote CamJam Quote  Post ReplyReply Direct Link To This Post Posted: May/02/2017 at 1:26am
Thanks Phil.  It was a NOS York, and I converted to 134a, using the recommended compatible esther-based oil. I wasn't surprised when the first seal blew as the compressor was sitting for 40+ years. I replaced that seal  myself about eight months ago, and the a/c seemed to work fine the last time I used it last summer. 

The only original parts were the evaporator and expansion valve. Everything else, including hoses, was replaced when the car was restored 18 months ago. 

I used a Santek brand front seal from Auto Zone. I had never installed one before, but it seemed simple enough… much like an inner wheel bearing seal, the main thing seems to be to make sure it goes in straight or you'll bend the shell. 

After installing that seal I evacuated the system for about 1/2 hour with a vacuum pump, but I've since heard that some let the pump run overnight, so maybe 30 minutes wasn't enough? 

I have another front seal on the way and plan to install it later this week. 




Edited by CamJam - May/02/2017 at 1:33am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pdok Quote  Post ReplyReply Direct Link To This Post Posted: May/02/2017 at 7:21am
Typically an hour is recommended. I'd let it sit in vacuum for 30 minutes after to see if it bleeds off after the pump shuts off.

Maybe second times the charm. Could be there was a nick in the seal on the way in.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 401MATCOUPE Quote  Post ReplyReply Direct Link To This Post Posted: May/02/2017 at 10:44am
Cameron...I NEVER put together any AMC system without replacing the Expansion Valve...but that is water under the bridge....the expansion valve would have no effect on the Compressor Seal.  I have had poor luck myself in successfully replacing the front seal, seems simple enough, but 3 out of 3 replacements blew the front seal again and I just replaced the compressor......that was with R-12, so not near as bad a hit with R-134a.  

Just make sure you if you lost system oil when the seal blew, put oil back in the system.

The best way to change the expansion valve is to remove the throttle pedal and drivers seat...that gives you enough room to use the TWO wrenches you need to break the lines loose.  DO NOT attempt to undo the nut on the hose, without backing up the tube from evaporator.......you may need to borrow a friends set of angle wrenches.

Hope this helps.....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote S Curry Quote  Post ReplyReply Direct Link To This Post Posted: May/02/2017 at 12:05pm
Forty two years ago this month, I started working at a AMC dealer. Folks were just starting to use AC and finding out that it wouldn't cool. I bet that month of May I changed out seals on 20 vehicles. Seal would dry up over the winter month and would fail when needed. Yes, I had to do a few twice. Keep everything extremely clean while assembling. Lint free rags are a must, too. I would vac down for 30 min. and charge up and run a leak test. Propane torch with a hose on it...........
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 401MATCOUPE Quote  Post ReplyReply Direct Link To This Post Posted: May/02/2017 at 12:40pm
Originally posted by S Curry S Curry wrote:

I would vac down for 30 min. and charge up and run a leak test. Propane torch with a hose on it...........

Steve/All,

I am not sure the R-134a and torch will work like it did with R-12.....BUT it was a terrible idea, the combustion by products are PHOSGENE GAS....aka Mustard Gas.....extremely toxic.  Phosgene Gas killed more people in WW1 then any other agent.

Phosgene is also known as carbonyl chloride (COCL2). It is formed when chlorinated hydrocarbon compounds are exposed to high temperatures.

This is from an HVAC site.......

When a refrigerant is decomposed or burned, the primary products formed are acids: Hydrochloric acid (HCI), if the refrigerant contains chlorine, and hydrofluoric acid (HF), if it contains fluorine. These products are certainly formed when hydrogen is present, such as from the breakdown of oil, water or if the refrigerant has hydrogen attached (like R-22 or R-134a). If oxygen also is present (from air or water), then it's possible to form carbon monoxide, carbon dioxide and various unsaturated carbonyl compounds -- the most notorious of which is phosgene.

Being extremely toxic in small amounts, phosgene formation was a real concern when traditional refrigerants (R11, R- 12, R- 113, R- 114) decomposed. Phosgene contains two chlorine atoms and an oxygen atom. It will only form when oxygen is present and only the refrigerants with chlorine attached will produce phosgene (not HFCs). R22 has only one chlorine atom per molecule, so it is extremely difficult, chemically speaking, to get another one attached to form phosgene. Decomposition of R-22 or HFCs may form other carbonyl fluorides, however they are not as toxic as phosgene.

Lets becareful out there!

Ross
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CamJam Quote  Post ReplyReply Direct Link To This Post Posted: May/03/2017 at 5:08pm
Thanks for the helpful advice, everyone!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 6768rogues Quote  Post ReplyReply Direct Link To This Post Posted: May/04/2017 at 8:34am
If you replaced the dryer, a short time under vacuum will do. If not, I leave 27 inches of vacuum on for 8 hours or so. That will test the system for leaks and boil out any moisture in the system. Water boils at about 70 degrees under 27 inches of vacuum, so it is a good way to dry things out if they are being reused.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote S Curry Quote  Post ReplyReply Direct Link To This Post Posted: May/04/2017 at 8:42am
Ross. Thanks for that info. Maybe that is why you don't see them anymore. I'm sure there are better devices for finding leaks. That is what we used. It was a hose attached to the lower side of the bonnet on a hand held propane torch. It would turn colors when finding a leak. Not very handy while under the dash. Would vac 'em down for a half hour, charge them up, do a quick checks for leaks and check high and low side pressure and out the door.....time was money!!
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