My welds aren't watertight..

[Countach919]

like the headline.. I've been making a 4 into one collecor for my exhaust, but in some areas I keep getting leaks (I test the welds underwater once they've cooled), what are the most probable causes? or how do I stop the damn leaks!!

Welder: Clarke 120E
Gas: Argoshield at @10L/min
Metal: 16 or 18swg steel (one of the pieces was found in my garage and may not be the best quality, all though it had no rust),
Believe the 4 pipes coming in are aluminised steel.

 

[130]

I take it you did the bit where the four pipes meet you weld the cross up between their ends, then run a weave up the sides of the pipes where they touch and are parallel with each other. That takes care of the joints between the pipes that you can't really get at otherwise.

I know that's probably a bit egg sucky, if so sorry.

A mate of mine used to check his welds (welding mini fuel tanks - I know I know) with soapy water as it bleeds through holes when there is no surface tension.

I used to use thinners to check mine, yep I know its flammable so that's a don't try this at home and don't do it its dangerous bit.

No warranty of any kind implied or given.

 

[Countach919]

Yeah I've done all the welding, (tack the 4 in pipes, then weld in the centre spider etc.) the problem is that when I pressure test them I et leaks (I block off the 4 exit pipes and attach a sealed airline into the end of the collector, then place the assembley underwater, and pump air into it & look for bubbles)... and she blows bubbles (NOT massively, but....
so must've done something wrong with the welds, question is, WHAT??? only blowing bubbles from a couple of places.

???

 

[Weldingartisan]

Small MIG welders are not the best for 'bubble tight' welds. It's very easy to get a near invisable pin hole at start up, when hot wire meets cold metal before a pool has formed. If looks are not important brazing will fill pin holes. W/A

 

[malcolm]

must've done something wrong with the welds, question is, WHAT???

Why not post a couple of pictures (good ones rather than mobile phone ones). Post honest ones and I'm sure someone will be able to diagnose the issue.

 

[lexi]

You got to get it right first time with Mig to be airtight. It may help to heat it. If you start from right to left and weld about 3 inches, then go back the same distance from where you started you should be able to catch the start of your weld while still reddish. If not then shorten your distance. Any little bubbles can be silver soldered or brazed.

Alex

 

[bigdry]

i guess this is why weld seam sealer was invented - no good for exhausts mind..... so if i seam weld a panel it porbably wont ever be water tight with a mig?

 

[malcolm]

It's seam sealer not weld sealer and is intended for sealing flanges that have been spot welded together. Though it can be handy for butt welded repairs if you do get tiny holes in them.

MIG can do perfectly airtight welds. A continuous weld is the most reliable way of making the join air tight.

 

[irondarren]

Im guessing here but as Malcolm says a continious weld should make an air tight joint. So if you have stopped and start, its likely to be leaking at the point where you started again, best thing to do would be to start welding over the point where you last finished say 6mm back from the end, means it is likely to have a large weld deposit at that point but it should be air tight

 

[oddball90]

One point did you clean the aluminised coating off the steel pipes?
Don