BC

I learned quite a bit last time I saw Rob, but now I am home with the right tools to test a recently gone through A/C system, and am not sure where to go next.

What was replaced:

Compressor seals
Compressor Lines
Large aluminum line in engine bay
Expansion valve ** (Issues may be here)
Drier
All orings

What I have is the old condenser, which I did not test. I may regret this.

And on the ** note above - The plate that seals the two hard lines to the front of the expansion valve is askew, and cannot be made to be flush. The larger line with o-ring is keeping this plate out a millimeter or more.

So I am able to get it down to 1500 microns normally, but when I turn off the pump, it will return to 10,000 microns within 2 minutes.

Is there a way to detect vac leaks here? I don't think I want to charge it unless I improve the situation. There is no rear A/C.

At any one time I ran the pump for 20 minutes. I understand it should be for longer, but that will not matter if I do not fix the leak(s).

I can use a different Condenser, but I do not wish to chase this without some better idea where the issue could be.

wpgshark

Are you sure that the system is dry? If there is any moisture in the system it will raise the system pressure as it evaporates. This is one of the reasons that a typical vacuum process is more than 20 minutes.

You can do a pressure test with an inert gas, typically nitrogen or Argon. If you put a little refrigerant in it before the inert gas you can use a leak detector.

Rob Edwards

If the expansion valve plate is not perfectly flush, then it's holding uneven tension on the circumference of the o-ring in there, I'd bet money that's the source of the rapid leak. I recall having that problem on the '90 GT (IIRC) but don't recall the fix other than getting it 'right'.

Speedtoys

Pump it up with nitrogen...*hssss*

Bilal928S4

That plate just holds the line to the expansion valve. You have to make sure the lines are seated all the way into the expansion valve and then screw the plate in. You cannot rely on the plate to correct the situation if the lines are not properly seated. Usually when you replace the expansion valve, you will need to play with the lines to get them seated properly. You might need to bend them slightly to seat properly.
HTH.

griffiths

That is a a major leak.

For something like that you could simply charge the system with
compressed air and listen for the leak or use the soap and bubbles.
If you have an electronic leak detector you could inject some refrigerant
and sniff it as well.

928 DesMoines

Is your setup still R12 or has it been converted to r134? I am on a similar path as you with my AC. If you have vacuum tested for 20 - 30 minutes, you have probably gotten all of the moisture out of the system, so you should be good on that front.
But yeah, re-check all of your work especially the expansion valve seat like Bil mentions.

If you are using R134, I would go get a can (like 14 bucks, at any auto parts store) with some leak dye in it. Put half a can in or at least as much as you need in order to get the AC compressor to turn on.
The dye will help you find your leak. It is your next step after you have re-checked your work and vacuumed all of the moisture out.


If you are still r12, you might (do the re-check and re-vacuum first) bring the car in to an AC mechanic that you know and trust. Should cost around 75-100 bucks for a leak test. Then you will know where the problem is. After the test and a good discussion with the mechanic, you can bring it home and do the work.


And yes, some people are servicing r12 at home, but that is a different discussion.

In my opinion of course

BC

Okay thanks guys. I'll continue working on it today.

BC

I'll google it, but where would I get nitrogen?

bureau13

I had what sounds like a similar problem with my expansion valve. I didn't have the large line seated properly, and when I tightened the plate, it caused the line to gouge the interior of the expansion valve such that it would never seat properly. I can almost guarantee this is the source of your problem, however if you didn't try to tighten the plate it might not have ruined the expansion valve.

It's easier to align that line if you remove the bracket holding the fuel cooler flush to the firewall, and loosen the fitting that connects that line to the fuel cooler itself. I found if I did both of those things, I could get sufficient freedom of motion to align it properly and then tighten it down.

BC

If it IS this, I should sure as hell know better.

I took everything off again, and the large line will not seat as low into this expansion valve as the smaller line does. I am going to clean everything and get another expansion valve as this was just in my box, and I have no idea about the origin.

Kevin in Atlanta

In the past I have used a set monster channel locks to hold the two outside plates parallel to the expansion valve while I tightened the plates down. Those tiny allen bolts do not always pull the plates into place.

dr bob

Expansion valves are precision instruments. Dropping one will ruin it internally for instance. Dirt, any dirt at all, will often cause it to function improperly. For all these reasons, any old ones should be tossed unless they are stored carefully and have a known good history. They are right below driers, IMHO, on the list of things that deserve replacement during service. The connections to the drier must be square and fully seated before the o-ring will do it's job. With your used expansion valve, make souble-sure that there isn't an old o-ring in the expansion valve preventing the suction pipe from seating correctly. Let's just say that this wouldn't be the first time such a thing has happened. Since it's a rigid connection from the fuel cooler, that cooler and the nuts that hold the lines into it must all be loose to start with, then all are drawn in evenly and slowly to make sure everything stays true as you snug everything up. Last step then is to secure the fuel cooler itself. I've seen some amazing 'work' on systems where there are obvious kinks in lines where pry bars have been used to 'help' move and realign the pipes. Gotta wonder at what the mechanic was thinking.

Did you get the dessicant air drier recommended in a previous/separate thread? If so, and you have fresh dry dessicant in it, you can use your dried compressor air to pressurize the system. Let the air in slowly so your air-line drier dessicant gets moisture out before the AC drier sees it. Using your regulator, set at 25 PSI or so, search for leaks with soap and water.

Speedtoys

You have a buddy with a welding shop?

BC

Thanks -
The expansion valve is not used. Sorry if that is not clear.

As I mentioned, I had it "in stock" but it could be an ebay piece that could be from anywhere. From what I can see, the large line has NO way of having it's shoulder sit flush when installed. Even with no o-ring, the shoulder sits 2mm out from the face of the unit.

I do have the large desiccant drier that I already had installed from before that thread - I mentioned it, but did not take a pic, so I think people did not see the part where I did... anyway - when I get the new part, I will reinstall and do all of this over and see where I am. I may also get the other condenser I have cleaned, as it may also be the issue.

I will do the air pressure thing after everything is together again if it does not hold vac - though I am afraid of what I may find if its not simple like the condensor or the expansion valve.