Welding in cats issue

[BreakMyWindow 1870]

So I had recently removed the cats from my M5, and replaced with mandrel bent pipes. This was all good and well, but am now having a bit of remorse since my car is an early M5 and uses about 1litre of oil every 1500 - 2000kms. With having no cats in place, it's a bit smelly and not pleasant on longer journeys.

I still have the original cats, but the ends which face the engine are double-walled. This looks like it may pose a problem with re-welding. Can anyone recommend a specialist or a technique that could be used to get these back in?

Side of cat facing engine :

Side of cat facing rear of car :

[KwS 2378]

Wouldnt that sort of oil consumption ruin the cats anyway?

[BreakMyWindow 1870]

Wouldnt that sort of oil consumption ruin the cats anyway?

You'd think so but the ones used in the M5 are pretty resilient.

[M5V8 337]

buggar.

luck of the draw mate. My 2003 M5 used oil also.

My 2002 - not a drop.

[westy 614]

Can you smell it inside the car?

Only way to reweld it is to remove the outer wall first, but you probably knew that

[BreakMyWindow 1870]

Can you smell it inside the car?

Only way to reweld it is to remove the outer wall first, but you probably knew that

You can on the odd occasion. Not pleasant.

That's what i was thinking, remove some of the outer skin, but the 2 exhaust shops I tried were not keen...

[BMTHUG 943]

I could do it. Easy way to do it is shave a little of the top layer off and weld the inner wall with mig then weld up the outer walls by joining a bigger diameter pipe over them. I used to be a marine engineer and came across these types of pipes on ships quite often and now as a mechanic Ive found Mercedes Benz pipes to be the same. Give me a yell if you dont come right with someone to weld it

[_ethrty-Andy_ 2122]

Can you smell it inside the car?

What does that mean?

I get that in the Van some times, i just assumed it was because its done 450,000km

[BMTHUG 943]

Wow good effort 450,000kms

[_ethrty-Andy_ 2122]

Wow good effort 450,000kms

original engine and feels like its done every single one no less

[westy 614]

What does that mean?

Usually exhaust gases are getting into the car somehow. Are you absolutely sure there are no leaks in the system.

I'm not too sure how much cats rid the gases of oil smells but would think you'd smell it cats or no cats.

[Michael. 2312]

That smell would just be a catless exhaust smell.

My new Soarer has no cats and it's really gross. When I re do the exhaust I'll be sure to use magnaflow highflow cats like I did on the E36 V8, much nicer when standing around the car while it's idling!

[KwS 2378]

i love the smell of raw, unburnt fuel.... cats are for wusses.

[BreakMyWindow 1870]

i love the smell of raw, unburnt fuel.... cats are for wusses.

You'd want to remove the gas cap in that case.

[BreakMyWindow 1870]

Usually exhaust gases are getting into the car somehow. Are you absolutely sure there are no leaks in the system.

I'm not too sure how much cats rid the gases of oil smells but would think you'd smell it cats or no cats.

Had a slight leak from where some clamping bushes join the exhaust sections together, but that has since been fixed with new clamps.

I'll smoke test the exhaust while I smoke test the crank case and the inlet side of the engine. pretty sure it's tight though.

[KwS 2378]

i do wonder, when the cats were removed, wouldnt they have had to weld to the dual wall pipe that was left on the car to fit the new pipe? Surely they could do it again?

[_ethrty-Andy_ 2122]

Usually exhaust gases are getting into the car somehow.

Oh i thought that whistling was my turbo spooling