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Solder on exhaust back box

Harry Bloomfield

Harry Bloomfield

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My diesel car's exhaust, has a rust hole, rusted from the outside, in, on the back corner of the outer skin of the back box. It was noted, though it wasn't leaking, and passed it's last MOT fine. It's a no longer available part, so would need to be specially made. I've asked a few places, over the phone, if they could weld a patch over the hole, but all suggest it just wouldn't last. It's a very heavy gauge unit, so I'm fairly certain a repair would last, but I lack the tackle needed for such a weld....

I'm wondering if solder would do it? Just how hot will a diesel back box get, would it melt solder?

I'm thinking to clean the area up, tin it, then cut a piece of steel to suit, tin that, then hot solder wipe it into place. Would that last, it's mostly cosmetic?
 
I doubt if it was possible to 'tin' any part of an exhaust system to allow it to accept soft solder. What about a toggle bolt with a good gasket on the outside. Either that or gas flame braze a light gauge patch over the area. Maybe if the metal was of a decent gauge, a TIG or MIG owner would be able to patch it.
Make, model and year so I know how the exhaust looks in its constituent parts.
 
Give it a go. You have nothing to lose and everything to gain. What about banding it with the fastening bolt(s) over on the good side of the metal and bedded on exhaust sealant. I've successfully banded a perforated box with that method before and it then sailed thru it's MOT. All the tester is looking for is gas tightness and safe fixings, otherwise custom-made exhausts would fail every time.
 
On the back rear corner?? SHYTE!! You're not going to attempt the repair whilst the exhaust is still affixed to the vehicle are you??
I had assumed the system had been removed for the repair. Have you seen a fierce fire caused by in-situ welding? There was one fairly recently on the nationwide news programme that wrote of that workshop and several others surrounding it ... don't do it!!
Now I understand why other repair establishments have refused to quote.
 
Never had much success mending exhausts. Only time it worked I bugg*red the good bit trying to get it back on. I have never bothered to try again!
 
I think you'll have trouble "getting enough heat in" and you'll need a flux to deal with your rusted steel.
You're at the upper end of what's possible with MAPP gas if that's what you're using. Hence the oxy-propane kits you see.

I'd pay my general car mechanic to do that, if he thought it worthwhile. He has a pile of metal, and part-exhasts which he cuts up to make parts to weld on to that sort of thing.
Won't last?? Not as long as a new exhaust, no, but a couple of years by which time there would likely be other issues.
Total actual mig welding time might be under a minute. Accessibility is a query if you can't get top access- a clamp and exhaust putty may be reasonable, depending. He did something like that on a car we kept only because the wife didn't want to let it go, which lasted in excess of 3 years which was long enough.
 
Scally-Ho said:
On the back rear corner?? SHYTE!! You're not going to attempt the repair whilst the exhaust is still affixed to the vehicle are you??
I had assumed the system had been removed for the repair. Have you seen a fierce fire caused by in-situ welding? There was one fairly recently on the nationwide news programme that wrote of that workshop and several others surrounding it ... don't do it!!
Click to expand...

I've had more than enough practice welding cars, this is right at the very back, and well away from anything flammable, and easy access, so no I wont be taking it off. It's a tremendous weight anyway.
Scally-Ho said:
Now I understand why other repair establishments have refused to quote.
Click to expand...

Those who were invited, never saw the job, they refused it based on their opinion that welding would just be a waste of time. Opinion, probably based on how light most exhaust system are.
Old Salt said:
Never had much success mending exhausts. Only time it worked I bugg*red the good bit trying to get it back on. I have never bothered to try again!
Click to expand...

I spent a year in Italy, officially working on a very extensive control system. I had the works only welder, dedicated to my 'team' doing the work. Whilst my 'team' were often occupied on other work, rather stop the job waiting for welding, I took it upon myself to learn to cut and weld quite passably. Often exhausts on fork-lift trucks etc., would need welding repairs, so - as I had the only welding equipment in the place, I would often as not end up patch welding them.
 
Harry Bloomfield said:
It's my Rover 75 diesel Contemporary.
Click to expand...

Guessing it's a saloon, as plenty of rear silencers available for estates?

Surprising that availability isn't good for a relatively recent car. Rimmers seem to have them. Admit that they're not the cheapest, some serious Googling required for something more affordable.

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Order your Rear Exhaust Assembly - WCG102831SLPP - Aftermarket ⛽ Low prices and fast, worldwide delivery ✈ British car experts ♚ Call ☎ 01522 568000 or ☎ 1-855-746-2767
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