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  #1  
Old 07-03-2005, 10:29 PM
Mike Murrell's Avatar
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Question Repairing R-12 schrader valve

I'm working on one of my old daily drivers, '87 Accord, and somehow managed to slightly damage the low pressure side schrader valve. I believe that the schrader valve is not opening because the can of R-12 is not getting cold when the can tap and low pressure side service valve are opened.

I've read about male thread chasers on one a/c parts site, but it looks like those were designed primarily for condensor/evaporator work. I'm wondering if anyone has ever repaired a schrader valve with something like a male thread chaser?

I may end up having to remove what charge remains, pull the hose, and let a local a/c shop install a new schrader valve to the hose.

If it weren't for the fact that I'm planning on selling the car, I'd more than likely go that route, but right now, I'd just as soon pursue any "gets it done" backyard approach.

Knowledgeable thoughts appreciated.

Thanks for your time.

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1991 300-SEL - Model 126
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  #2  
Old 07-03-2005, 10:37 PM
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Why not change the valve core yourself? It's no harder than a valve core in a tire. Unless your definition of 'slightly damaged' means 'butchered beyond all hope'.
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  #3  
Old 07-03-2005, 10:38 PM
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Test the valve with the car off by pressing in the valve with the head of a finish nail.. if you get a squirt of pressure , the valve is working , but your hose pin may not be going on far enough to open valve.
You can test that by putting hose on before opening can and loosen hose at can and see if pressure is coming back up the hose from the port.
Or, use gauges [ you asked for backyard approach, so.. no gauges]

If the outside threads are what you are talking about, then you have to die them clean again..
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  #4  
Old 07-03-2005, 10:43 PM
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I find that the valve is a constant source of leak even if it is new. It must be complemented with a metal cap with a rubber or o-ring gasket inside.
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  #5  
Old 07-03-2005, 10:48 PM
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Quote:
Originally Posted by Oreo
I find that the valve is a constant source of leak even if it is new. It must be complemented with a metal cap with a rubber or o-ring gasket inside.
I agree .. the metal flare ones without the ring always leak.. more so when not using the a/c b/c the pressure is higher on the low side charging port than when a/c is in use...find many a leak right there...
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  #6  
Old 07-03-2005, 10:49 PM
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Arthur:

Yes...I'm talking about the outer threads; not the depressable valve.

Are there any mass-marketers..ie..Sears, etc. that might sell a tool suitable for this re-dyeing?

I have R-12 gauges, but am simply trying to avoid having to extract refrigerant, remove hose, pay for hose repair, etc.

Thanks.
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  #7  
Old 07-03-2005, 11:05 PM
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Quote:
Originally Posted by Mike Murrell
Arthur:

Yes...I'm talking about the outer threads; not the depressable valve.

Are there any mass-marketers..ie..Sears, etc. that might sell a tool suitable for this re-dyeing?

I have R-12 gauges, but am simply trying to avoid having to extract refrigerant, remove hose, pay for hose repair, etc.

Thanks.
Oh I see. Not the valve core. I'd say your best bet is to find a thread file and go at it. I don't know offhand what thread pitch the service fittings are, but I could find out tomorrow (daylight) if that'd help.

Thread Files
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  #8  
Old 07-03-2005, 11:18 PM
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$$$PIT:

If it won't cut into your 4th of July holiday, I would appreciate that information.

Thanks for your time.
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1991 300-SEL - Model 126
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"Fräulein"
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  #9  
Old 07-03-2005, 11:28 PM
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Quote:
Originally Posted by Mike Murrell
Arthur:

Yes...I'm talking about the outer threads; not the depressable valve.

Are there any mass-marketers..ie..Sears, etc. that might sell a tool suitable for this re-dyeing?

I have R-12 gauges, but am simply trying to avoid having to extract refrigerant, remove hose, pay for hose repair, etc.

Thanks.


Sure .. Sears is as good a place as any..
Just ask for a 7/16x20 die...

PS ... seeing its a Holiday, you may even have a friend with a standard tap/die set .. that die is in any regular tap/die set.. nothing special about the thread... I would put some grease/petro jelly on the treads to catch the
metal the die is going to cut away and then wipe it w/rag. .turning CW.. lastly, just get a quick squirt from the valve stem by depressing it to have the system pressure blow what is left in the valve out of it to be sure ...
Gerry rig works great at times of dispair..
I have even gone so low as to make a die out of a flare nut by cutting a pie shape out of it as a relief and screwing onto the male .. it actually will cut threads .
Good Luck..

Last edited by Arthur Dalton; 07-03-2005 at 11:48 PM.
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  #10  
Old 07-03-2005, 11:54 PM
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Arthur:

Thanks for your help.
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  #11  
Old 07-03-2005, 11:58 PM
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I see Arthur saved me a trip to the toolshed. Good luck with it.
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  #12  
Old 07-04-2005, 09:09 AM
LarryBible
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There are special tools available that let you change the schrader valve without loosing the charge. I've never used one and have never figured out how they work, but you can get them at places like ackits.com and acsource.com.

Good luck and Happy Birthday USA,
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  #13  
Old 07-04-2005, 10:02 AM
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Something I've ben wondering for awhile, are the A/C valves that much different in the seals from a tire valve? The R12's are the same size, so can a tire valve core be used to repair a leaking R12 valve?
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1980 500SE/AMG Euro
1981 500SEL Euro
1982 380SEL
1983 300TD
1983 500SEC/AMG Euro
1984 500SEC
1984 300TD Euro
1986 190E 2.3-16
1986 190E 2.3
1987 300D
1997 C36 AMG
2003 C320T 4matic

past: 1969 280SE 4.5 | 1978 240D | 1978 300D | 1981 300SD | 1981 300SD | 1982 300CD | 1983 300CD | 1983 300SD | 1983 380SEC | 1984 300D | 1984 300D | 1984 300TD | 1984 500SEL | 1984 300SD | 1985 300D | 1986 300E | 1986 560SEL | 1986 560SEL/Carat | 1987 560SEC | 1991 300D 2.5 | 2006 R350
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  #14  
Old 07-04-2005, 11:10 AM
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Quote:
Originally Posted by Johnhef
Something I've ben wondering for awhile, are the A/C valves that much different in the seals from a tire valve? The R12's are the same size, so can a tire valve core be used to repair a leaking R12 valve?
Been a while since I bought any, but I can't imagine the correct core costing enough to make this substitute tempting. GM specifies that the valve cap with rubber seal is the seal for the service ports, and not the valve cores. Your mileage may vary.
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  #15  
Old 07-04-2005, 12:25 PM
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It was more of an availibilty thing.

Back when I charged my 124, I found one of the cores to be leaking after removing the hose. It was a saturday and parts was closed so I used one of the tire valve cores we had extras of.

The car is still holding its charge today.

I was wondering more of any long term issues, if any. the parts are identical to the eye.

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1980 500SE/AMG Euro
1981 500SEL Euro
1982 380SEL
1983 300TD
1983 500SEC/AMG Euro
1984 500SEC
1984 300TD Euro
1986 190E 2.3-16
1986 190E 2.3
1987 300D
1997 C36 AMG
2003 C320T 4matic

past: 1969 280SE 4.5 | 1978 240D | 1978 300D | 1981 300SD | 1981 300SD | 1982 300CD | 1983 300CD | 1983 300SD | 1983 380SEC | 1984 300D | 1984 300D | 1984 300TD | 1984 500SEL | 1984 300SD | 1985 300D | 1986 300E | 1986 560SEL | 1986 560SEL/Carat | 1987 560SEC | 1991 300D 2.5 | 2006 R350
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