Exhaust leak - where to start?

[james_ly]

So I had a slightly fluttery exhaust, now after a track day it's progressed to sounding more like an air cooled Beetle...
I don't really have time to crawl under the car yet, would it be worth taking the manifold heatshield off first or am I wasting time? Any common areas to check first?

[thetyrant]

I have similar, mine has a ebay catless manifold and when i bought it was leaking from 2 badly fitted gaskets where it bolts to catpipe, changed these and sorted it but now its started again, changed the same 2 ring gaskets at that join but its still blowing so suspect its teh flex's on the cat pipe, need to get under it and investigate further but its such a slight leak hard to pinpoint, i was hoping it would get worse after last track outing but it hasnt!

If your on stock manifold with heatsheilf and nothing has been touched then its probably either the 2 ring gaskets where it joins to cat pipe or the flexi's in cat pipe both of which seem most common, rest of system seems pretty robust.

Another thing to check without getting under car is that 02 sensors havent just come loose, had that before on another car and was nice easy fix just nipping them up.

HTH

[Carolyn]

A long screwdriver.  A flap of tissue/blue roll/kitchen towel taped to one end.  Offer it around all the joints/suspect areas.  It will flutter when next to the leak.

[james_ly]

Ah thanks. I replaced all 3 O2 sensors about a year ago, they may have worked loose as I nipped them up really. Definitely worth trying.
So access to the cat pipes is from underneath or is it possible to reach through the engine bay?

[thetyrant]

Ah thanks. I replaced all 3 O2 sensors about a year ago, they may have worked loose as I nipped them up really. Definitely worth trying.
So access to the cat pipes is from underneath or is it possible to reach through the engine bay?

Yeah check them O2's could be a simple fix,  cat pipe access and is from underneath and if flexi's are blowing you can either replace those by welding in new ones which is a bit fiddly or buy a new cat pipe which are about £100 on ebay/ cats2u website etc. 
It might just be 2 ring gaskets where catpipe bolts to manifold as well but unless its been apart they should be ok, worth checking though before buying anything else.

[Alex Knight]

Flexis.

[james_ly]

Didn't have time to crawl under the car, but I can feel air escaping on the left side of the manifold. Can't really see what's down there but is that the flexi?

[Joesson]

James, sometimes you just have to get down (and dirty)

[james_ly]

James, sometimes you just have to get down (and dirty)

/sigh
Exhaust coming off then I guess

[Joesson]

Use Carolyn's "flag" waving technique before you start dismantling, best to have the enemy in your sights.

@Carolyn would you advocate the Redex smoke test for finding an exhaust leak on a 2?

For the younger generation:
A shot of Redex into the induction side and run the engine while bunging up the exhaust pipe. Smoke Signals indicate any intermediate points of exit.
I don't know what it would do to a modern system but it worked on 60's cars.

[Carolyn]

Use Carolyn's "flag" waving technique before you start dismantling, best to have the enemy in your sights.

@Carolyn would you advocate the Redex smoke test for finding an exhaust leak on a 2?

For the younger generation:
A shot of Redex into the induction side and run the engine while bunging up the exhaust pipe. Smoke Signals indicate any intermediate points of exit.
I don't know what it would do to a modern system but it worked on 60's cars.

Hmm.  Don't know how that would work with a self-tuning car like ours.  I'll have to do the experiment (one day!).

[james_ly]

I got lazy and took it to a garage. It was the flexi, one side was practically hanging off. Garage just fitted a new cat, and I can hear myself think again (y)

[Alex Knight]

Called it.