Any tips for welding an exhaust?

[Nicola&Tony]

I'm a novice welder but I want to have a go at welding some small holes in the silencer box for our lt. I'll post some pics of the holes when the rain stops. I've got the exhaust off the van at the moment.

Just wondering if anybody has tips / advice about doing this sort of thing. I guess the main problem will be blowing holes in thin steel (I have 0.6mm wire in my mig so hopefully that will help) and the fact that I'll probably not be able to clean it back to shiny steel (I've never tried welding rusty stuff before).

I'll be using CO2 for the shielding gas but would make a temporary switch to an argonCO2 disposable if it'll make this job easier / more successful.

Any info would be much appreciated.

Cheers

Tony

[CovKid]

Better to weld patches but you may find its too thin generally to take it.

Is yours the early box (ie exhaust comes into box from behind, or the ends?)

[Nicola&Tony]

It's the exhaust on our vw lt31 camper project. The exaust pipe enters the silencer on the end. Its about 1" below where the pipe enters the end of the silencer where the small holes are. A patch would be difficult because the surface isn't straight, there's a profile in it.

Tony

[campercrazy1]

you cant weld rust, so go at it lighlty with a wire brush first and see what its takes- if it falls apart put a patch in, but if s pretty knackered and you've got it off anyway plus and your splashing out on new gaskets anyway,it maybe better to bite the bullet and get a new one-be weary of false economy!

[Nicola&Tony]

Just found a pic that I took last wknd when the exhaust was still on the van.



Tony

[CovKid]

Trying not to dampen your enthusiasm but I think you'll struggle on that. You need shiney metal and thats not going to be easy, plus if its thin there, it'll probably be thin in other areas too. You could cut a disc of metal and weld it on to complete end possibly - be more to weld to then.

[Nicola&Tony]

. . . You could cut a disc of metal and weld it on to complete end possibly - be more to weld to then.

That's an idea, think I'll try a semi-circle and see if I can patch over the lower portion of that end panel.

Tony

[weldore]

turn the welder down low and try and do a line of weld either side of the hole and bridge the gap
just co2 will be fine for that
dont try and do a run..do lots of on and off's and leave a sec or 2 between

if it doesnt want it then make a patch for it

if that doesnt work....gum gum

TBH though..i dont think it will be long for this world

[Plasticman]

Hi, think you'll struggle with the mig, gas it no problem but thats not going to help you
mike

[Rozzo]

bleedin pessamists
just clean it back to good metal tone (even if that means makin the hole 3 inch long by 1 inch wide) then tap the area as flat as you can get it (that ridge will knock flat) and then cut a slightly oversized patch, start on/offing at one end and tap it down onto the box as you go whilst its glowing red. simple m8

you have nowt to lose by trying and will feel really good if you salvage it.
did you get those bolts out?

[Ian Hulley]

TBH though..i dont think it will be long for this world

Agreed, sadly

How much is a new one ?

Ian

[HarryMann]

Agree with Rozzo... doable, if you have some MIG experience (or want to gain it) and **
or gas weld (or braze filler plate with lots of flux) as MM says?

Hit it hard with a wire brush (stainless brush is best*) to find widest extent of perforation
Straight C02, 1 Max or 2 min, feed 5.5 to 6 (on a Clarke 150TE), thicken edges with on/off/on/off, then join them up, if you can't move in and fill bigger holes, then thin cover plate, keep brushing all the time to remove any contamination...

Just develop the technique of thickening the dodgy edges, if they burn back further, then brush again, move back with them, thickening and working all around damage... **

You can do the whole circumference where the pipe joins an exhaust end-plate that way (usual place that starts fracturing when rusted thin), uses loads of wire, and looks a mess but it fixes it... once holes filled, can work over whole area with normal weld pool method, smoothing it and filling any suspect pinholes (or block them with anti-rust or gun gum).

Make sure you finally brush all weld clean, degrease and treat with something good (Pure Zinc Weldthru spray or RC900), even if you think it'll burn straight off, parts of silencer don't all get that hot, anything to stop it rusting immediately. Every month or so, check, brush and re-spray...

Can sometimes keep such an exhaust going for a year or so that way, even a fractured pipe mid-system... can be a stiff-neck jobbie though, so if underneath, take a pad to rest head and a very powerful light with you...

* Stainless wire brush benefits
** Be patient, be persistent, if an edge burns, go back further and build it up again, eventually you'll get to good metal

High temp paints Halfords do them a lot cheaper

[CycloneMike]

Tony,
I know you are keen to have a go and I don't want to discourage that.
With time practice and patience I am in no doubt it can be repaired. My concern would be that just the start o fthe repair it will need as chances are the rest of it is also paper thin. And it will become the back box version of trigger's broom!
As Ian says have you looked at the cost of a new one? The longer this thread and the other one goes on , the bigger your shopping list get!!!
By the time you buy paint alone I would guess it comes close to a quarter of the cost of a new one, which you can then fit forget and move on to something more fun.
Just a thought.
Regards,
Mike

[Nicola&Tony]

Thanks very much for all the info and ideas, very much appreciated. I found one place online that has a new silencer, £170 delivered. I need to ask vw how much it would be from them.

I will have a go at the repair, out of curiosity as much as anything (to see if I can do it, good excuse to get the welder out etc), but I'm prepared to bite the bullet and get a new one if necessary, although I'd much prefer to spend the money on a stainless exhaust, but guess that this would have to be made-to-order somewhere?

Rozzo, those bolts in the photo are still there at the moment, the exhaust is off the van in one long length from tailpipe through to the catalytic converter. Those bolts will need undoing with the angle grinder I reckon (the other ones did at the end where the cat is).

Tony

[T'Onion]

Tony , is the silencer the same as what's on the diesel ? or is it completely different cos of the cat ?
I think mine has a side entry and end exit ? If so then they are £50 ( ebay delivered)

I'd have a go at migging it ,