Baffled by exhaust noise

[B5NUT]

I've got a couple of noises from the exhaust, and cannot figure out what it could be. The fist is a whistling noise, which I have been told it's normal on a turbo, with the windows down you can hear it but you cannot with them up. It also only happens when the revs are above 2000.

The second noise is what I can only describe as if the the exhaust is blowing, I've checked the system this evening and I cannot find any holes, and it's just had a new flexi section which was a genuine part.

now I do believe that the cat is on it's way out it's an 1996 A4 1.8T, so 14 years old with 119K on the clock and I know it's still on the original cat, mid section & back section. The car is not down on power and is running fine, there are no fault codes on the engine.

 

[aragorn]

cracked manifold?

 

[B5NUT]

****** never thought of that! I take it the only way of checking would be to remove the manifold.

Also, if the cat is knacker would that cause a blowing noise? (or is that just wishfull thinking)

 

[aragorn]

The cat can sometimes split the weld at the flange where it bolts to the turbo. It wont always come apart, but it can leak?

 

[phoenixv6quattro]

Mine had a whistleing noise (2.8 v6 with milltek). It turned out to be a tiny hole on the nearside downpipe just before the cat. Instead of making the usual blowing noise it was whistleing. The most annoying sound only audible beyond 2k or when stepping hard on the gas. It drove me mad.Gone now though.......

 

[B5NUT]

I just changed the down-pipe section, the whistling noise is annoying but I'm more concerned about the blowing noise.

 

[hardhitter]

Have you checked the gasket between the cat and turbo ?

 

[B5NUT]

No but I was going to take the manifold off, so will replace all the gaskets in that area. Another fun weekend ahead