Exhaust leak- MOT failure

[mk08]

Hi All

My car failed MOT on:

1- Rear upper exhaust has major leak of exhaust gases
2- Rear upper exhaust emissions likely to be affected by an exhaust leak box

I took it for repair. One mechanic said it needs a replacement (£120) and the 2nd mechanic said he can weld it for £40.
Not sure if it needs welding or replacing, can anyone guide me please.

Thank you in advance.

[underwhelmist]

If you get the damaged bit welded, there’s likely another bit waiting to blow. I’d just replace it.

[E-bmw]

mk08 said:

Not sure if it needs welding or replacing, can anyone guide me please.

Not without seeing it.

[Tony1963]

For the peace of mind, £120 is a bargain for a replacement. As posted above, if repaired you’ll just be waiting for the next leak, and it’ll never happen at a convenient moment.

[paintman]

Impossible to say whether your particular welding job is likely to last but IME with welding bits of leaky exhaust up you are often simply postponing the inevitable and you are likely to find you spend £40 now & will soon be needing to spend £120 to replace it.

So it will be costing you £160 instead of £120.

[GreenV8S]

Welding an old exhaust might make sense when you're doing it yourself for the cost of the gas, but it's very unlikely to be worth paying somebody to do it unless you plan to sell the car the next day.

The weld is a temporary fix that will probably need more work in a few months whereas the new exhaust would last for years. When you compare the long term costs it is not remotely close - replacing the exhaust will save you a lot of money in the long term.

[mk08]

Thank you all for replying. So I decided to pay £40 for welding. I asked the guy not to apply patch (or bandage) but to weld it.
I went to collect the car and he showed me the following 2 pictures. I asked what this red line is, he said don't worry about it.
I am no sure if it's welding or just a sticky patch/tape?

[sociopath]

I think it's the colour of regret for not listening to the advice you were given on here.

[paintman]

I see you've gone for the £160 option.
Silencer boxes usually rot from the inside out.

I have absolutely no idea what the red stuff is and if he'd welded a rectangular strip of steel onto the box I can't see any reason for it to be there either.

[Milkyway]

Looks like those liquorice strips that we used to buy.
( should have used the black one though for an exhaust repair)

[brman]

I reckon the bit welded on it was recycled from an old car panel or other bit of metal. The red is the paint he didn't bother to clean off. To be honest, I would have left the paint on too, there is no point turning a £40 quick fix into a £50 quick fix just to make it look pretty

The others might be right about it being a temporary fix although there is something slightly odd there. Is that the top of the box we are looking at? Because normally they rot at the bottom where the condensation sits.
If I am right (and the rest of the box looks ok) then it might have been a poorly made seam that went. In which case the repair might last longer than people think.....

[GreenV8S]

mk08 said:

I am no sure if it's welding or just a sticky patch/tape?

That looks like paint on the bit of scrap metal he used for the repair. Nothing to be concerned about. Don't be alarmed if it smokes a bit when it burns off the first time the exhaust gets hot.

I wouldn't be surprised if it needs further repairs before long but to be fair that box doesn't look in terrible condition and it might last a while yet.

[kambites]

As someone said above they tend to rot from the inside out - when you use cars for journeys too short for the exhaust to get up to temperature properly the hot damp exhaust gases hit the cold exhaust and condense so you end up with a puddle inside the exhaust which obviously rots through the bottom of the silencers. How long it lasts will depend on how many short trips you do, but you probably ought to get at least a year or two out of the patched box.

Assuming that is that that's the bottom of the box. If it's the top, something very odd happened to it!

[bluezedd]

mk08 said:

Thank you all for replying. So I decided to pay £40 for welding. I asked the guy not to apply patch (or bandage) but to weld it.
I went to collect the car and he showed me the following 2 pictures. I asked what this red line is, he said don't worry about it.
I am no sure if it's welding or just a sticky patch/tape?

Agree that the red stuff is whatever was on the metal patch.

He has definitely welded that. I'd be happy with that for the 40 pounds to get it a ticket on it but I'd also not be upset down the road if it rots through again.

It might last a long time. It might not. He has tried to help you by keeping costs down.

I agree though that I would've gone for the replacement if I was keeping the car, but would have gone for the bodge if it's a bangernomics last mot type deal.

[paintman]

Yep.
Makes sense.
The black ridge round the red bit is the crispy remains of the paint that was on whatever it was he cut the patch off and the red bit is the unburnt paint.