Can you braze header tubes?

[Danny_Ocean]

I've got a very slight separation in the weld on my cat bypass pipe. It is not much bigger than a hair...not a crack, but seems the weld just didn't "stick" in this area. I don't want to remove the pipe from my car if I don't have to.

Using the appropriate rod (bronze/brass?) and oxy/acetelyne, can I braze this gap?

[Flat6pac]

I d take it to a muffler shop and have them MIG it. If you put heat flame on it, it could warp the pipe
Bruce

[Danny_Ocean]

Originally Posted by Flat6pac

I d take it to a muffler shop and have them MIG it. If you put heat flame on it, it could warp the pipe
Bruce

MIG won't burn through? (The other issue I have is the car is lower than a gnat's azz, so I'm not sure it could be lifted at your local muffler shop).

[Joe Bob]

Shouldn't be an issue if he has an old school open pit. Wire fed with argon shielding gas would be a snap.....

[ClickClickBoom]

Take it off and have it properly welded. TIG, everything else is half way. It would take a good TIG guy about 3 minutes, of which 2 would be set up. If it is aluminized all bets are off. Is it leaking?
eric

[Danny_Ocean]

It's barely leaking. You can see some carbon at the joint (which is how I discovered it).

I own a MIG machine...but don't know how to use it. The neighboring shop are welders. Perhaps I can have them use my machine on it (or run an extension cord from their shop). There is a guy there who knows how to TIG, but he's barely around and isn't very reliable. Don't want to deal with him if I don't have to.

[aston@ultrasw.c]

I suspect the flange is significantly thicker than the tube, this makes it a difficult weld. Too much heat and you burn holes in the tube, not enough and you get pigeon **** (technical term) on the flange.

A braze would be an acceptable repair. All you need is a seal, the strength comes from the weld. Assuming the rest of the weld is up to scratch.

A brazed joint needs to be prepped carefully. It must be completely free of oxide, paint, grease etc. Get in there with a grinder and open it up a bit, wash out with acetone etc... Then brush flux onto the joint, don't just dip the rod and braze away.

It could be repaired with mig, tig, O/A whatever, it just takes more skill and experience. Brazing is a simpler, low risk choice.

[MT930]

Originally Posted by ClickClickBoom

Take it off and have it properly welded. TIG, everything else is half way. It would take a good TIG guy about 3 minutes, of which 2 would be set up. If it is aluminized all bets are off. Is it leaking?
eric

TIG is the right way, a good TIG fab guy could do it on the car in 5 mins.

[Rot 911]

Back in the day we used to just close those gaps up using oxy/acy and a piece of coat hanger for filler!

[donporfi]

Like Rot 911 says you can close that gap with an oxy/acy. It is not that difficult. TIG is overkill for that task. Actually most shops use MIG.

[Canuck_Targa]

If you have a mig in your shop, just see if one of the neighbors could come over and weld it. Wire brush it off (that looks like high heat silver paint) to clean it up before he does it. You won't burn through the pipe (if the guy knows how to adjust his welder).
There is no need to TIG weld repair a MIG welded part, the original weld is mig so repair it with mig.
Unhook your battery before he welds it, so you don't get any current spikes through the cars electrical.

[swade]

Also have them attach the ground on the piece itself if possible or as near as possible, good call on pulling the battery cables to protect electronics.