Welded Cat. Box - OK For MOT? | Technical matters | Back Room Forum

Sat 29 Apr 2006 11:04

Welded Cat. Box - OK For MOT? - rg

Folks,

The middle exhaust box containing the cat. on my 2.5 Citroen XM (diesel) has rotted on the entry pipes at each end. Milesage is 114K.

The box is made of a decent gauge steel, and the rot seems to be very localised around the welds. The rest seems perfectly sound.

My intention is to get this weleded up, rahter than waste money and resorurces on a new one.

Is my MOT tester going to spot this and fail me? Welded patches on exhausts were, IIRC, acceptable in "the olden days" (if the boxes had enough "meat" left on them).

r

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Sat 29 Apr 2006 11:18

Welded Cat. Box - OK For MOT? - Number_Cruncher

>>Is my MOT tester going to spot this...

Possibly

and fail me?

Not if the repair is gas tight.

Number_Cruncher

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Sat 29 Apr 2006 13:08

Welded Cat. Box - OK For MOT? - bell boy

they are usually made of stainless steel or galvanised and therefore not usually worth welding as they spit more than weld.
Very easy to get blood poisoning from welding galvanised steel as well as the weld burns much brighter than mild steel and you need a different mask,also if grinding it down to prepare for welding the debris is injurious to health

buy a new un,,,,,or a good second hand one.

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Sat 29 Apr 2006 13:43

Welded Cat. Box - OK For MOT? - SjB {P}

I'm, in a similar situation; bar the back box replaced a few weeks ago (when the weld on the inlet pipe failed), the exhaust system on SWMBO's 306 1995 Sedan is original, including cat. The weld where the pipe meets the middle box failed a few days ago though, even though the metal work itself (pipe and box) is in tip-top shape.

Looking at the cat case though, it is very rusty and I can see where it is likely to fail (at a weld) soon.

Rather than repair either I will replace the lot especially as the cat has now had 11 years of catalysing anyway. Cost is about £190+VAT for the cheapest "non-OEM but OEM quality" cat I can find (an OEM cat is £320+VAT), and £92+VAT for a OEM exhaust direct from Peugeot.

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Sat 29 Apr 2006 14:20

Welded Cat. Box - OK For MOT? - dieselhead

Safe to do a weld repair on an exhaust if the aluminium coating is ground away and a dust mask is used - although you need to do much more welding than a couple of runs on an exhaust box in poorly ventilated conditions before it would make you ill!.

For a 1995 306 order a front pipe for a pre cat 1993 306 turbo diesel which are about £25 compared to over £100 for the cat pipe.
A non cat front pipe might also be available for early XM diesels although welding would be cheapest option if the box is basically sound..

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Sun 30 Apr 2006 18:46

Welded Cat. Box - OK For MOT? - blue_haddock

SjB - drop me an email as i may be able to do something with the price on the exhaust and cat.

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Thu 4 May 2006 16:33

Welded Cat. Box - OK For MOT? - SjB {P}

Thanks for the kind offer, blue_haddock, but I spotted it too late; the replacement exhaust and catalyst are now fitted. At least I spent the money at my very helpful Pug indy and have no qualms about putting some dinner on their table!

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