welding exhaust centre to cat

[BrokenBiker]

so we are obviously talking about the megane again.

basically I have been under it 4 times in the last 4 months now, as no matter what I do the centre section somehow works its way loose from the cat. it is a flared joint as usual, with the correct clamp as tight as I can get it. thing is the clamp is still tight, but the exhaust has somehow moved back and now the joint is loose and blowing, again, I can shake it about with my hand and there is obvious flex where the joint is, as soon as I loosen the clamp off, slide it all back as it should be and tighten again it is fine for about 3 weeks, then the same happens and im getting fed up of it

so, does it sound like a sensible thing to weld the centre to the cat. im wondering if I should just seam weld it, or just get 4 decent tack on it then seal up with gun gum paste (as I have tried before, it just cracked off when the exhaust moved.

obviously if wither the cat or centre section need changing it is going to be a harder job as I will have to cut the exhaust from this cat, re weld the new one etc but for now im just looking at stopping this happening.

 

[zzr1200]

I'd be inclined to cut the down pipe and install a flexible exhaust joint depending on the support mountings/room for the cat, but compress the flex joint the amount the original joint pulls apart, so its always tightly pushed in, if you get my drift...

http://www.ebay.co.uk/itm/like/2213...ff3=1&ff11=ICEP3.0.0&ff12=67&ff13=80&ff14=108

hth

 

[Robotstar5]

Just put a couple of plug welds in to stop it moving and keep the clamp to stop it blowing, you can drill the plugs out if necessary in the future.

 

[BrokenBiker]

well ive just got under it and it needs something. I'm thinking just tack the bottom up and then clamp it as said.

i don't wanna mess about cutting bits out and welding in flexi pipes. Too much for a daily runner.

 

[gordon stephenson]

Drill it in a couple of places and put a couple of stainless self-tappers through both sections of pipe and then clamp up, Would be easier to remove exhaust if ever needed.

 

[FranV8]

I suspect you're seeing the symptom not the cause, check your engine mounts aren't on the way out, just securing it all together it'll either blow again or break somewhere else. (had a Corrado that did the same thing)

 

[BrokenBiker]

engine mounts are good and fairly new. Exhaust hangers are on the way out but after being under it today i noticed the flared section of the centre pipe, that fits onto the cat, is only 25-30mm deep, where as on the back its 3 inches. Think this may have a lot to it as its pretty much just holding on by the bare minimum.

in not too worried about having to replace it to be honest, if the cat goes i can get a full stainless steel one price system inc cat for the same price as the cat anyway so will probably do that.

haven't time today so tomorrow probably will just tack it up and see how it holds for a few hindered miles

 

[wookie]

Can you join two exhaust clamps together with some flat bar, so one clamps the joint (as per normal) and the other goes further up the inner pipe after the joint and is clamped there. You could also weld a couple of blobs only on the pipes just inside of the clamps so the pipes can't slip past.

That should stop it moving, and much better than welding it up solid, just incase you need to remove/replace anything in the future....

 

[norlander]

"does it sound like a sensible thing to weld the centre to the cat." -dunno but the RSPCA might give you a hard time if they hear about it.

 

[dan.taylor.1]

Having had two meganes of he mk1 persuasion I'd say silicone it then just put a tack or two (don't go mad as it'll be a bastsrd come the time it needs changing etc!) You may find it's got the wrong cat or centre on it as there are quite a few types, and a lot of aftermarket stuff was wrong, I made my own in the end after trying three suppliers and them all been wrong..!

Dan

 

[BrokenBiker]

well I used a trolley jack to lift it to the proper height, made sure everything was joined properly, got a decent sized tack on the bottom, a tack on each side, then clamped down as tight as I could with the exhaust clamp, smeared some gungum paste around the joint and ran the engine on idle to warm it up and harden it off a bit.

will be taking it work tonight so will see then if it moves agian

 

[dan.taylor.1]

Exhaust sealant is meant for between the mating surfaces of the pipe not round the outside of the joint btw. And I'd use black silicone/rtv as it has always worked better for me, flexes a bit rather than cracking.

Dan

 

[BrokenBiker]

gun gum isn't meant to be used as an assembly paste, it is a repair paste to seal small holes or splits, or to seal up blowing joints after they have been assembled and the assembly paste has deteriorated

firegum is what you are referring to. it is an assembly paste meant to be liberally applied to the inner pipe and then allowed to harder to form an air tight seal. gun gum has fibres in it so when applied it acts similar to fibre glass, creating a hard and solid surface to cover any damage

 

[dan.taylor.1]

You're right, missed the bit about gun gum. I hate all exhaust sealant tbh! New gaskets and a smear of silicone did me well when I worked in garages, and when I did a stint working on quads and tractors!

Dan

 

[norlander]

I just realised you have posed a question similar to one I was going to ask. Basically, I want to weld a bracket on to a silencer with a cat. I'm not too fussed if I damage a bit of the cat, what I'm more concerened about is will it turn into a big firework if I start welding on it?

 

[AndyStobbs]

nope.

 

[norlander]

thanks 4 that