compression fitting on aluminum?

[davem]

Here's an odd one. :)

My Astro has rear A/C, and the refrigerant is carried back there through 3/8 (mic'd at 0.377) and 3/4 (0.757) aluminum tubing. I replaced the line set last year after it sprung a leak near the rear tire. This year the new set is leaking in the same place. I would like to cut and cap the rear air lines up near the engine and just use front air.

Anyone know if I can use a brass compression fitting on aluminum tubing?

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[John Bridge]

Sounds like a designed in engineering shortfall to me. Dave, forget the brass. Just whittle out a wood plug and drive it in there with the butt of your margin trowel. :)

[cx]

NOT what John said. :D


Guarantee it won't work for long, if it works at all, Dave. Usta do plenty aluminum tubing in a very early life. Flare (double flare was required on all aircraft hydraulics) fittings are the only style I know that work well with aluminum. So, get you a flare nut and an aluminum flare plug for each size and pewt'em on there.

Or bring it over by my casa and we'll just crimp'em shut and weld'em, eh? I doubt you have a TIG machine in your garage, but do you have an acetylene torch? Easy enough to find some rod to braze that crimped tube shut.

[davem]

Tried to braze the the first line set shut CX, but didn't take into account the oil in the 134. Maybe I could do better this time. I was thinking about taking it to someone with a tig welder, probably be cheaper than the $90 line set. Any ideas where a person not involved in your former line of work could find aluminum plugs and such? :)

[cx]

Yeah, gotta be clean, clean, clean to use the aluminum brazing method. Also gotta remember to have the other end of the tube open, or at least not sealed, lest you make pressure whilst heating and drive yourownself nuts trying to close that last little hole. :)

If you'll suffer no consequence except for having to cut off the fittings and do it over (and re-charge, of course), you could try the compression fittings if you have some on hand. Problem with aluminum is it likes to move about a lot with temperature change and the aluminum is gonna act differently than the brass ferrule. You can probably beat the corrosion problem by coating the parts with Noalox, a product made for coating aluminum wiring when connecting to copper lug terminals. Available at HD in electrical section. Worst case, it leaks; best case, it don't leak until you have sold the car. ;)

You can sometimes find aluminum fittings at your local NAPA store. If they don't have such in stock, they will have a catalog with some to order. Might be kinda like finding Schluter stuff at HD, though, might hafta 'splain them that they can get the parts. A maintenance facility at your local airport will certainly have some, but they'll charge you like they're for an airplane, which still might not be all that big a deal.

Might consider the torch again, too. Clean, clean, clean, fold it over and hammer it flat and braze real quick.

[John Bridge]

Okay, okay, maybe the wood plug isn't such a good idea. How about force feeding the tube with modified thin set? :)

[genel]

Hey Dave,

Have you chased the lines down to see where the connect to the compressor circuit? They might be attached with threaded fittings there, it might be easier to disconnect them and cap them off where they start.

I would think that if you cap the lines far down on the run that you will have a hard time with the charge. The liquid line may act as a receiver and store an unpredictable amount of liquid which could make the whole thing act flakly.

BTW: did you know that, when heated, R-22 produces phosgene gas? I have no idea what happens to 134a when heated. If you weld, be sure its pumped down good first.

[davem]

Hi Gene,

There are two line sets. One comes from the engine to approx under the driver's seat. The rear set goes from there to the back. I had to replace the low pressure one to the engine last year, but don't remember the fitting type. I can't even see where the high pressure line goes.

I assumed that having it capped would be the same as having it turned off at the dashboard, meaning no circulation of the 134a. Is this not right?

I had planned on whacking the lines about a foot behind the driver's seat coupling area. This way I can take the two one footers and plug them by whatever means, then put them back.

Thanks

[genel]

Having the turned off is not quite the same as having them capped off. When charging the system both evaps have to be open to get the right amount of charge in the system. A capped line would fill with gas first and might only fill with liquid over time.

But if the stubbs are just a foot long its not going to make any difference anyway. I thought you where going to cap them inside the wheel well.

We had a suburban that was done that way that we used off road. I always worried about the lines, never did anything about it, just worried.

Good luck.

Gene

[davem]

Actually, the stubs for the rear line set will be 1 foot, but the front lineset comes back at least 4-5 feet if you were to stretch them. I just looked and remember from last time. The high pressure front line comes out of a welded tee up near the compressor. No good trying to cap that one.

Crap, now I'm thinking about ordering another rear lineset, so it can rot out after a year. :(

Maybe if I put shrink wrap tubing along the whole length it'll last 2 years. ;)

[Sonnie Layne]

John, I think you and I need to go have a brew while the big kids work this one out... I originally thought of a broom schtick. Heck, we'll have Jim and Rob along and I'll order a good Ozzie Shiraz. :)

[tomtuttle]

Beer or wine...make up your mind!! :D:D:D

[Sonnie Layne]

see there??? this whole discussion has me cornfuzed. ;)

[bbcamp]

Sometimes I find Ozzie Shiraz to be overly sweet and excessively laden with one dimensional fruit that can be overwhelming. I was weaned on MD 20/20, so Oz is a moderate step up for me. Then, there are times when only a fermented box of the kid's grape juice will do.

[Sonnie Layne]

overly sweet and one dimensional??? Have you met my former wife???? :)

I'm sure there are such things, but I've not found it from that grape from that area. Matter of fact, I find ..... oh.... what were we talking about??? It was such a dizzying subject I had to get off topic. I'll send you some offerings that are anything but one dimensional, tho, Bob. Just 'cause you're such a nice guy. Considering you're an engineer and all that :D:D:D

[bbcamp]

Hell, I don't have any idea what we're talking about. I did a web search on Ozzie Shiraz, and found some pretentious wine expert doing a review, so I copied that first line. The rest is mine. If you're gonna send me anything, send rum, preferibly from the Virgin Islands. :D

No wait, I'll go get it myself! :D :D

[flatfloor]

Dave I once had an aluminum A/C tube line that was broken. I took it to a radiator shop. They fixed it right up.

[davem]

Thanks Jim, I took the line set off last night. There's a nasty corroded spot right where the clamp was in the wheel well. Do you know how they fixed it? I've been tempted to go get some braze rod and try to fix it, but am a wee bit skeerd. If I could get a pro to do it I'd rather do that. Damned thing is over $150 from the dealer. :(

[flatfloor]

Dave, these guys do both AC and radiators, it's been awhile but I believe it was a Tig welding job as CX suggested.

[flatfloor]

Could there be some electrolitic action going on there?

[davem]

The clamp has a neat ribbed rubber liner to prevent metal/aluminum contact, but I think those ribs hold dirt and such. I bet the real problem is the dirt road I drive down to get to work. They spray it with calcium chloride to keep the dust down. That stuff gets under the car and sticks like crazy.

[cx]

Mmmm. My experience (not recent, but substantial) is that it is exceeding difficult to make such a repair with any torch-applied rod. They're just not real workable on un-clean surfaces. :(

TIG is also sensitive to corrosion, but it's still a lot more workable in such situations. Fella can frequently start back where there's clean metal and bridge over the bad parts. May be ugly, but maybe seal the leak, too.

Sounds like a design problem, Dave. Can you change out the line from one threaded fitting to another? I'm thinking I would maybe replace that aluminum tubing with a reinforced rubber line. Ain't gonna be so sensitive to all that road salt and dirt. This would be possible?

[davem]

They have a crappy non-standard type fitting. I don't know if someone could use the ends and replace the bulk of the line. Do you think someone good with a tig could put a patch over it and weld all 'round it?

[davem]

Here's a picher of the line set, a close up of the corrosion and the non-standard ends. The lines under the car fit inside these ends, and has an o-ring on them.

[cx]

Yep, somebody could do that easily enough, Dave, but can you find somebody who would do it?

I welded an aluminum tube from the AC on my previous Nissan pickup. It had cracked near the mount block at the compressor. Only lasted a week on the first try. :( Lasted more than a year on the second try, though, then I changed trucks. :)

It's just not the kind of repair most welding shops wanna do. I think flatfloor may be on the right track with the radiator shop, though. They do that kinda repair on a regular basis.

But then you gotta do something to keep it from happening some more. Maybe some of that undercoating stuff they sell in spray cans at the auto supply store. Put the lines back in and pookey the bejesus out of'em. Real pain in the ass next time you gotta fix'em, but..........

Hell, try some epoxy, maybe you could start a new bidness if it works. :p

[davem]

Even though Kelly was joking, I though I'd so something dumb just for grins. I got me some JB weld (they're from TX too!) and pookied the hole shut. Sprayed the whole damned line with a can of rubber undercoat and put it back on. Tonight I vac'ed it down for about an hour and a half and charged it up. Nippy cold. :) If it holds, I'll be pleasantly surprised. If it don't, I'm out a coupla bucks and maybe learned a little something. I'll post updates on it as time goes by. :)

Maybe you can read all about my success on the back of the JB Weld package sometime in the future! :D

[cx]

Dave gonna be famous! :D

Friend had a riding mower. Muffler kept falling off. Was a pipe s'pose screw into the engine block, but the threads had gone away. I pewt it back in there with some JB Weld and let it set up over night. Made it through most of a mowing season. I was most impressed. Did it almost as a lark, but damned if it didn't almost work, even under that kind of heat and vibration.

I like the stuff. :)

[Sonnie Layne]

Yep, dem JB Weld folks put 'em up a nice mansion along I30 just outside of Sulphur Springs. (I did the landscape design several years ago). Right nice folks, at least the folks I dealt with. If you pay attention. It's one of the best epoxies that I'ver run across, but you have to pay attention to details, as is the case in any adhesive/cleaner.

I've still got a thermo-thingamabob, some kind of sensor that determines when the airflow is to be changed (we used to call them butterflies) glued together with JB. That's been over 10 years ago after I had a fire under my hood from the alternator.

Anyway, it's good stuff if you get the prep work done. Don't know that it's any better than the next best seller, but he's done a hell of a job on marketing.

And, he's Texan!!!! :)

[cx]

Tryin' to find weird parts reminded me of this.

You still got AC in the back seat, Dave?

[davem]

Back seat and front. Brrrr, it's chilly! :D

[cx]

Most excellent! I think you're on to somethin' here, Dave. :)