Exhaust advice

Horizon81

Joe_Horner wrote: »

Bear in mind that a new (especially aftermarket) exhaust is going to sound different to the old one. They often sound a little "tinny" until they've been run for a while.

Oh it sounds tinny alright, very tinny! I was more concerned about the fact that when you block the tailpipe, you can see and feel exhaust gases coming out of the join on this joint. If the olive (aka gasket) was missing then I would have thought it would be possible for them to have used a ring of gum instead then mated the 2 unions together and put through the 2 bolts and tightened them up. I dont understand what you mean by saying it would be impossible to keep it there while it set.


And are you saying the engine wouldnt provide enough pressure at idle to blow a rag/hand off the tail pipe?

Richard53

Joe_Horner wrote: »

Agreed with most of the above, but the MOT rules were "clarified" a couple of years ago and a leak is only a fail if it's "significant". An exhaust that won't create pressure at idle (especially with a petrol engine) can easily be a pass under that description.

Incidentally, from the danger point of view, most catalyst equipped cars don't produce enough carbon monoxide to be a problem once the cat's lit up and it'd take a VERY big leak to fill the car with enough CO2 to suffocate you!

OK, a 'significant' leak - reference to the MoT test was to indicate that it is not just a cosmetic/nuisance issue for the owner of the car, it is actually a testable item. Perhaps the stories of people being killed by faulty exhausts are old wives' tales, but I would still rather the stinky stuff was carried away safely rather then allowed to ruin the 'ambience' of the interior

Horizon81

Actually, scrap what I wrote above, it's not an olive joint. Look at the union on the right hand side where the mid section connects to the back box. Essentially 2 flat oval shaped plates come together and are tightened up with 2 bolts. This is the sort of union I'm talking about. I don't know what it's called though!

salubrious

There should be a sealing ring in between the pipe flanges.

If a new sealing ring was used - No jointing paste is required.

colino

Take it back and get them to fix the leak. Sounds like there wasn't a good match with the flanges and they've tried, unsuccessfully, to bodge it up. It's not going to self heal and just a matter of time for the engine management light to come up.

Joe_Horner

UsernameAlreadyExists wrote: »

Depends where the leak is!

True, but anywhere behind the cat (which I'm guessing the back-box is ) will have such a low CO level (if the emissions are in spec) that you'll suffocate from lack of oxygen before the monoxide gets to you.

Along with most cars of its era, the Yaris has a max CO level of 0.5% but in good fettle will have a level of almost zero.

Horizon81 wrote: »

Oh it sounds tinny alright, very tinny! I was more concerned about the fact that when you block the tailpipe, you can see and feel exhaust gases coming out of the join on this joint. If the olive (aka gasket) was missing then I would have thought it would be possible for them to have used a ring of gum instead then mated the 2 unions together and put through the 2 bolts and tightened them up. I dont understand what you mean by saying it would be impossible to keep it there while it set.


And are you saying the engine wouldnt provide enough pressure at idle to blow a rag/hand off the tail pipe?

Exhaust assembly paste is too runny to form a ring with until it's been heated and starts to set. Even most repair pastes (which include fibre filler mixed in to give some support) won't stay in shape for long until they're heated.

As for a hand over the end, a car with a perfectly sealed exhaust will blow it off but, at idle, a 1 litre engine is pumping so little gas through the exhaust that even a very small leak will let the pressure escape.

It does sound like, in this case, they may have made a poor job of sealing that joint but sealing new pipes to existing sections can be a problem, even with new sealing rings, so probably not an outright bodge.

It's worth asking them to have another look though

Richard53 wrote: »

OK, a 'significant' leak - reference to the MoT test was to indicate that it is not just a cosmetic/nuisance issue for the owner of the car, it is actually a testable item. Perhaps the stories of people being killed by faulty exhausts are old wives' tales, but I would still rather the stinky stuff was carried away safely rather then allowed to ruin the 'ambience' of the interior

No, exhausts on older cars can certainly kill, as can leaks before the cat on a new one - especially if they're in a position to get sucked into the air vents. Or, like on old Beetle heat exchangers, are effectively in the air vents!!!

And I totally agree that it's better to have it outside the car - carbon monoxide may be odour- and taste-less but exhaust gasses as a whole certainly aren't