Not looking good for AC in my '92

I have been trying to find where my leak is in the AC system of my '92 convertible. After carefully examining every connection today, this is what I found. I hope you can see the crack in the fitting of the evaporator where the muffler connects. Any ideas how to get around this. I am trying to source a used evaporator without too much luck.

And before I hear that I don’t need AC because it is a convertible and I have gotten away without it for the last 18 years, I was planning to take the wife to Virginia in late June in this car. If you have ever been stuck on I-95 around Washington DC you would understand.

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I may just try this.

[US Part Number: 80631] US Part Number: 80631
Canada Part Number: N/A
Permatex® Thread Sealant with PTFE

Category: Thread Sealants

Economical general-purpose fitting sealant. Outperforms tapes and pipe dopes. Seals and resists pressure in air, oil, diesel fuel and hydraulic systems. Remains pliable at higher and lower temperatures. Temperature range -65°F to 300°F (-54°C to 149°C); resists common shop fluids.

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Additional Information
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Suggested Applications: Air conditioning fittings, temperature sending fittings, and hydraulic fittings

Yeah, thread sealant won’t work.

I hope replacing the evaporator on a '92 is easier than on an '83.

Honestly, I think I’d be thinking about a bodge. Like, assembling the hose to the fitting with copious amounts of JB Weld or something similar. Whattaya got to lose? If it doesn’t work, the evap needs to be yanked out and tossed anyway.

No kind of glue or sealant is going to work here.

My advice… have the crack brazed. I would do it both on the inside and out.

In preparation take a hard rubber ball that will fit tightly in the pipe. Drill a small hole through the middle of the ball and push a small (unbreakable) wire through. Now tie off one end with a large metal washer. You can now push the ball tightly down in the tube to catch any debris from the brazing or filling to make it smooth. Just a few drops of compressor oil will keep the ball from heating up. The brazing on the outside will require you to use a Dremel tool to clean up the threads. Before you pull out the ball with the wire use a small vacuum attachment to suck out any debris.

The key here is to make ABSOLUTELY sure nothing goes down that pipe. A small amount of work and expense compared to (gasp!) removing and replacing the evaporator.

You think that crack can be brazed in situ?

Not sure if you’ve got enough room to try Laco Heat-seal stik or if it would work in this situation, but I used it on a cracked fitting on my AC condenser and 4 years later it’s still working.

It’s a heat activated epoxy that sets up in seconds. You heat the area then push the stick on to the hot fissure and it melts to fill the gap. Heat-seal stik© is available through A/C suppliers or online (probably!) Not recommended for long-term use so HVAC techs generally use it for “get you going” repairs until they can source new components.

I suppose you could try it in combo with that permatex you mention, it would be like a epoxy “braze”

Anyway, it fixed my leaking condenser so I’m sold on it!

If brazing in situ is a possibility, how about simply replacing the entire elbow? I presume it’s brazed or soldered onto the end of a tube coming out of the evap. I dunno where you get a replacement elbow; perhaps off of any evap in the junkyard. Can the cracked one be removed and a new one installed in situ?

And another idea: Find a replacement fitting (doesn’t need to be an elbow) and machine the lower end of it to fit snugly within that opening in the cracked fitting. Then braze this new fitting into the existing one, so the brazing anchors the extension and seals the crack all at once. The new fitting would sit a bit higher than the original, but that can be dealt with.

It appears to me from the photo that there would be enough room to braze the fitting … BUT … ?

In my hierarchy of life there is oxygen - air conditioning - food and water in that order ! And yes being based in DC during my airline days I had the (pleasure ??) of being stuck on the beltway in the middle of summer MANY times. The mere fact that I am here today is a testament to the efficiency of my commuter car’s A/C system :sunglasses:

I just ordered some of the Laco Heat-Seal Stik from Amazon. I think this is worth the $30.00 gamble. I will have it on Saturday afternoon. Hopefully I will have an answer before the weekend is over.

I have not been able to confirm it but I was told SCparts in the UK has these evaporators custom made for them that they sell for around $450.00.
Thank you,

The height is locked in as the muffler that attaches to the fitting just barely clears the brace in the engine bay.
I would be concerned about starting the car on fire trying to braze the crack or a new fitting on to the evaporator. If I am not mistaken you need to heat the fitting up to 1100 degrees for brazing.
The La-co Heat-seal stik that Larry mentioned only needs to go to 350 degrees.
I am also a little concerned in being able to re-create a good sealing surface from a brazed fitting using a dremel.
Good ideas though, thanks,

Jeff …

I would never knock a product that I haven’t tried, so good luck with the Heat-Seal stick. But obviously there is no way to test the fix until you’ve pressurized the system either with nitrogen or an evacuation and full charge with refrigerant. So there’s a little more involved then “it’s worth a try”.

For a permanent fix I would still go with the brazing though. If you properly prepare the surroundings for protection from the heat you should be fine. As far as cleaning up the weld remember the only thing that actually seals the union is the very top of the fitting where it presses against the “O” ring.

I am fully aware of the testing required to verify the repair. The first test would be to verify that it will hold a vacuum. If I have success with that then I would charge it with nitrogen to verify that it can hold the pressure. Only then would I proceed with a charge using refrigerant.
Also, I believe that the sealing occurs between the ID and OD as the depth of the slot in the AC fittings exceeds the o’ring thickness, so no matter how hard you try you can not compress the o’ring which may explain how this had occurred in the first place. If this doesn’t work I may consider brazing it but I would probably use a reamer to smooth out the braze in an attempt to recreate the seal surfaces accurately. Doesn’t brazing require a gap to function effectively? I seem to recall .0015" being optimal for a good repair. Other than the flux, is there some other method to remove any oil residue from the crack that I would need to perform?

The '94 must be different than the '83 in this regard. The only thing that connects to this fitting on the '83 is a hose, and the OEM hose on my '83 didn’t fit well at all, when I rebuilt the system I modified the hose a bit to make it fit better.

There is this muffler that attaches to that fitting and then the hose. The '89 doesn’t have this muffler so I believe it was part of the facelift change which also eliminated the fuel cooler.

I have done a lot of micro brazing in my life, I do jewelery amongst other things, and if you decide to go this way this is my advice:

Use an acetylene - oxygen torch with the smallest flame possible.
Use silver solder, super soft, the one they use for stone setting bezels.
Cover with a metal sheet the back or the foam will really suffer. Remember that in order to braze the metal has to get red red hot.
The flux and the fire will clean the oil residues., anyway there is no way to clean inside the crack…
No need for a gap.
Braze only the inside, if you braze the outside your thread will be destroyed.
Get some pieces of brass and practice before. It’s very easy to melt the whole thing, so be very careful.
On assembly use the Laco Heat-Seal Stick or something to seal because I don’t think it is possible to close he crack all the way up to the top without destroying the mating surface and also there might be micro holes left.

My 2 cents.

Well, now I can see why that fitting cracked. Too much weight hanging off it.

As some have suggested, put a fitting that tightly pushes into the cracked fitting. Braze it. Get a new hose made up minus the AC muffler. Pretty sure it’s will work just fine without it.

My 92 xjs also had a leak in the evaporator, but the core itself was leaking, so after a $2400 estimate I decide tackle it myself. First of all, I found a new aftermarket evaporator on the internet for about $100. The steering wheel and airbag need to be removed as well as the entire dash panel. If you are very careful and patient and have some mechanical experience and expertise it can be accomplished. Mine is still working 4 years later.

I wonder if you can seal this with an external o-ring on a pipe which is a sliding fit into the existing elbow. If the inside of the top part(below the crack ) is round then an o-ring in a suitable sized groove on the outside of a pipe could be slid down the bore and retained by the original nut. Suitably sized joints of this type can withstand very high pressures.