VW Polo exhaust manifold - weldable?

[Crater Creator]

Hi,
Just looking for the collective's wisdom on a wee job.
My stepson's 2001 VW Polo 1.3? has cracked another exhaust manifold and started blowing. He has already replaced it, but with a used item - so no telling how many miles it had on it already.
He's short on cash - so I have told him it MAY be possible to weld the crack.
Anyone know if these are weldable? It doesn't look cast, looks like some sort of formed steel sheet.
As I won't get to it for a few days I would just tell him to get another replacement one if I'm not going to be able to do anything with it.
I've got MIG (preferably) or TIG available.
Cheers lads.

 

[Rig Pig]

The last manifold I tried to weld was on my scimitar years ago, I failed dismally with arc but it brazed OK.

 

[zx9]

Hi,
Just looking for the collective's wisdom on a wee job.
My stepson's 2001 VW Polo 1.3? has cracked another exhaust manifold and started blowing. He has already replaced it, but with a used item - so no telling how many miles it had on it already.
He's short on cash - so I have told him it MAY be possible to weld the crack.
Anyone know if these are weldable? It doesn't look cast, looks like some sort of formed steel sheet.
As I won't get to it for a few days I would just tell him to get another replacement one if I'm not going to be able to do anything with it.
I've got MIG (preferably) or TIG available.
Cheers lads.

Slightly off topic, if it is making a habit of cracking exhaust manifolds do you need to be looking at the cause perhaps shot engine / gearbox mounts or incorrectly supported exhaust?

 

[The_Yellow_Ardvark]

Braze it.
I never had any joy welding an exhaust manifold.
Last one I did was on a Renault Cleo, the owners son had lowered it and tried to lift the car on the down pipe on a curb.

I had it off, down to a friends place, good clean out, a bit of a V cut and away I went.

 

[Crater Creator]

Braze it.
I never had any joy welding an exhaust manifold.
Last one I did was on a Renault Cleo, the owners son had lowered it and tried to lift the car on the down pipe on a curb.

I had it off, down to a friends place, good clean out, a bit of a V cut and away I went.

Right got it - brazing it will be then. I suspected that might be the case, just wasn't sure with it looking like non-cast stuff.
I don't have oxy-acetylene, just a small propane torch, but I could get a cheap carbon arc attachment for the welder. It's starting to sound cheaper to just get a new manifold though.

@zx9 - yeah there must be something causing it, I'm suspecting he may have stressed it somehow when he recently dropped the sump to fix a drip. The problem was likely attached to the handle of the ratchet spanner.

 

[hotrodder]

Got a picture of it? The only Polo manifolds i can find pics of that aren't cast iron have a cat built into them like



and none of them appear rusty enough to be mild/carbon steel? Wouldn't be suprised if they're 409 ferritic stainless?

No idea about Polos but some car/engine combos are infamous for manifolds cracking through fatigue/heat cycling rather than only failing as a symptom of something else... the 3.2 straight six in my daily for example is pretty much bomb proof but it's relatively common for the smaller 4 pot models to suffer from cracked exhaust manifolds

 

[Crater Creator]

Got a picture of it? The only Polo manifolds i can find pics of that aren't cast iron have a cat built into them like

View attachment 95119

and none of them appear rusty enough to be mild/carbon steel? Wouldn't be suprised if they're 409 ferritic stainless?

No idea about Polos but some car/engine combos are infamous for manifolds cracking through fatigue/heat cycling rather than only failing as a symptom of something else... the 3.2 straight six in my daily for example is pretty much bomb proof but it's relatively common for the smaller 4 pot models to suffer from cracked exhaust manifolds

Yeah I think that's the one. Can't get back to check until the end of the week but that definitely looks like it. Last time it cracked up near the exhaust flange.

 

[normspanners]

thats the usual place for them to break, I have welded them with dissimilar rods and have used mig too and they have lasted, Rover K series freelander etc it was quite a standard 'service job' for them to fall apart.

 

[Crater Creator]

That's great gentlemen, thanks for that, very useful info. So I'm assuming these manifolds are stainless?
I will have a go at MIG on the manifold with standard MS wire. If that doesn't work then I might get more exotic with the TIG (just ordered some dissimilar SS TIG filler rods just in case).

 

[The_Yellow_Ardvark]

Check before you weld.

I was in a VW specialist breaker nabbing a bit for sister Golf. I asked about the 1300 Polo. The manifold can be 1 of 3 types.
They looked very similar and do the same job, but Dave said they are made rom different metals, depending were VW got the parts and were they were assembled.

 

[Crater Creator]

But would dissimilar TIG work whatever steel it's made of? I know there are weld beads on the thing from the factory, and I'm pretty sure it's some sort of steel rather than anything weird like titanium, it's just a cheapo runaround....
Worst case if I screw it up he'll just need to buy a new one - back to plan A.

 

[normspanners]

If it WAS welded it WILL weld. IMHO

 

[Crater Creator]

I'll let you know how it works out and either post a picture of the manifold melted to bits or nicely welded up. It could go either way.

 

[hotrodder]

A disimilar like 309L would be my choice as that'll work with any of the usual material suspects. If they're stainless 409 is the flavour OEMs favour for exhaust stuff, it's very magnetic and light/patchy surface rust is fairly normal. Mild steel wire will physically work but as with the 300 series it can produce some funky metallurgy and result in brittle welds. More detail on welding ferritic flavours of stainless here http://www.twi-global.com/technical...of-ferritic-martensitic-stainless-steels-101/

 

[dannyp]

the non cast ones weld just fine with normal steel mig wire, reliablity wise ive had more luck with with bog std A18 wire than dissimalar. what dose help lots is to remove any soot before hand from the inside if possible

 

[Crater Creator]

Just a quick follow-up. I never got a chance to take any pictures but it welded up great with MIG.
It was, as expected, detaching where the manifold is attached to the enoine flange, when in the vice I could see it coming away when giving it a pull.
A clean up with the rotary wire brush and a bead of MIG round the end pipe held it all firmly in place. Price of one new manifold saved.
Also he had thought the lambda sensor had failed, but we reset the code after welding the exhaust and it seems like the sensor is OK too - may have just been pulling in air.
A good 300 quid in parts saved there, I'm well chuffed - he is even more so as it would have been his money!
The dissimilar rods will have to wait until another day to get tried out.....

 

[tazz]

good on ya boss

 

[cianh91]

Most vw parts engine blocks included weld well they generally used good material iv seen a corner of a golf block welded back on and its still going