Automotive Air Conditioning Information Forum (Archives)

jeep_bum on Wed August 16, 2006 4:33 PM

Year: 2004
Make: jeep
Model: Grand Cherokee
Engine Size: 4.0
Refrigerant Type: R134a

Obviously if the relief valve passes air, it is bad. . .but at what psi? Can I just blow through it (lung powered) to see if air comes out or do I need a higher psi(compressor powered). . .say test to 200 psi?

I guess the question is when a relief valve blows, is it completely open (little to no resistance) or can it still hold a decent pressure, but not what it used to and still be bad?

I have the system apart and I just wanted to see if there is a simple test.

Thanks
Jason

Chick on Wed August 16, 2006 5:48 PM

If it didn't blow on you, leave it alone. "Most" are set to go off at around 450 to 500psi, but "most" will not reseat and will leak after releasing the refrigerant. Some will hold tight afterwards , but you have no way of knowing until you charge the system... If yours blew before the system was taken apart, change it before putting it back together..Otherwise, just leave it alone... Hope this helps..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

jeep_bum on Wed August 16, 2006 6:12 PM

I guess that is part of the problem. . .not really sure it did blow. I found oil leaking down the compressor so I'm checking the o-rings and the compressor. The valve was just next on the list of things to check.

I'm not the primary driver. . .and I don't know that my wife would know if the valve blew -- I've never heard one go off before -- of course there are a lot of noises on a car that I would notice that she wouldn't. ;-)

Thanks

Chick on Wed August 16, 2006 6:26 PM

Some will just let a stream of refrigerant out, some will make a popping sound with the steam like appearence of the refrigerant/oil. "If" there was dye in the system, hold a UV light on the little hole in the middle of the vlave. Should not see any dye, if you do, change it. But in your case, I'd change it anyway, and find out what type of failure you had..As I said, I've seen them re-set themselves, but more often than not, they did their job and are now shot..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

jeep_bum on Wed August 16, 2006 8:58 PM

Thanks for your insight on this Chick.

I guess replacing the valve brings up another issue which other folks have dealt with. I have alread tried the jeep dealership to get the valve, but they want to sell the entire manifold on the side of the compressor to a tune of ~230$.

Through searching the forum there doesn't seem to be a consensus on where to get replacement valves. .. except the junkyard. . .which brings us back to testing valves. These valves were obviously designed to be replaced. . .you'd think it would be easy to order a new one!

Well, I'm about to pull a vacuum and see what happens -- but if anyone knows a good source of relief valves please chime in.

Thanks
Jason

iceman2555 on Thu August 17, 2006 10:37 AM

Many of these valves are not serviceable parts....ie the hose assm containing the valve. Chrysler seems to lead the industry in 'non-serviceable' parts.
Thankfully, usually this type valve does tend to reseat itself.....however, there is always the exception.
Suggest to evac the system....recharge with 12 oz of refrigerant......run engine (compressor not engaged) to normal operational temps...this adds a bit of extra heat/pressure to the system....check the valve for leakage. If the valve is not leaking......finish the recharge and retest. Hopefully all will be well.
Good luck with your repair.

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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

iceman2555 on Thu August 17, 2006 10:39 AM

Opps forgot....when system is functional....test all cooling systems to ensure proper operation. If the valve did indeed 'vent' there is a root cause...this must be diagnosed and repaired.

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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

jeep_bum on Thu August 17, 2006 11:33 AM

Well, as for the reason it blew in the first place, I'll chalk that up to my ineptitude -- I tried charging the system. . .and it must have had air in it. This was before I found this site and read the mastercool book of course! Since then, I have flushed every component (except the exp valve and new drier).

I did pull a vacuum last night and let it sit. . .I got it to about 28Hg and it was at 27Hg this morning. I assume this is unacceptable.

The valve is just a bolt on part with an o-ring; it looks like they at least thought about making it a serviceable part. It looks like the ac-delco part 15-5711 mentioned in an earlier post -- the one on the left in the pic at this link

15-5711


but I have no way of knowing if these are compatible. . .I assume that all relief valves will blow at about the same pressure so it would be a matter of fitting.

Anyone know if there is a standard size of relief valve?


Thanks for the comments!
Jason

Chick on Thu August 17, 2006 11:53 AM

Some are course thread, some fine thread..Best take it off and stop at a junk yard. Get a used one off a core, because you do have to match the threads...Hope this helps.

I'll post a pic of what I mean when I get home tonight...If that will help..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

Edited: Thu August 17, 2006 at 11:54 AM by Chick

jeep_bum on Thu August 17, 2006 3:01 PM

Mine is a coarse thread (10m x 1.5) -- I took it to home depot and tried threading it through different size nuts.

I did find out my compressor is a nippondenso 10pa17e --so it's to the junkyard this weekend

Thanks for all the help!
Jason

Cussboy on Thu August 17, 2006 3:09 PM

A few years ago I over-filled my 1988 B2200 truck a few ounces of R12. A few days later, sitting at idle a few minutes(Arizona, 115 degrees), the compressor relief valve (an updated model) spat a small amount of refrigerant and oil (popping sound). I didn't need to do anything, as it re-sealed fine, and worked fine. Obviously, most don't experience temperatures of 140 degrees 3 feet off the paement as we do here. Previous to that compressor being used, there was what was called a "heat fuse" screwed into the receiver-drier which would crack and leak out rerigerant to "save" the compressor from those high pressures (I lost one of those, and my R12 as well, during an earlier 115 degree day, so I repalced that with a plug).

Chick on Thu August 17, 2006 6:28 PM

Quote
Originally posted by: Cussboy
A few years ago I over-filled my 1988 B2200 truck a few ounces of R12. A few days later, sitting at idle a few minutes(Arizona, 115 degrees), the compressor relief valve (an updated model) spat a small amount of refrigerant and oil (popping sound). I didn't need to do anything, as it re-sealed fine, and worked fine. Obviously, most don't experience temperatures of 140 degrees 3 feet off the paement as we do here. Previous to that compressor being used, there was what was called a "heat fuse" screwed into the receiver-drier which would crack and leak out rerigerant to "save" the compressor from those high pressures (I lost one of those, and my R12 as well, during an earlier 115 degree day, so I repalced that with a plug).

I still can't see how you guys can live in that heat...

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

jeep_bum on Tue August 29, 2006 2:18 PM

Just a quick update

I vacuumed the system and charged it and the relief valve held, but the expansion valve had gone bad somewhere along the process. So I replaced the expansion valve and got everything vacuumed and charged and now all is good. The A/C works, good pressures/performance, and the relief valve evidently did reseat. Just in time for Fall!

The inability to find a new relief valve for this compressor is still frustrating, but I guess that will have to be a frustration for another day!

FYI Chick, I confirmed they started using expansion valves in the 2002 Grand Cherokees.

Thanks everyone for all the help.

Jason

Jason

JoshuaSulwer on Sun August 09, 2015 4:01 PM

i see this was in 2006 and the internet shopping has come a long way since then. Now days anyone reading this, you don't have to go to a junk yard, a simple search on the web will find you brand new relief valves for 15 bucks or so... Would really love if someone would take the time to explain how to know if a expansion valve is bad...

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Thank you