Twilight Zone exhaust issue

[carlo]

Something very weird happened today.

 

405 was fine all day, used it then parked up for a couple of hours.  When I started it up again sounded like the exhaust had fallen off, dreadful racket.  Had a look underneath 'cos I thought perhaps it had snapped, couldn't see anything amiss.  Then slowly the noise starts to clear, sometimes loud sometimes normal, until it had completely gone and the car was fine and as normal.  Drove home without drama and has been fine since.

 

What was all that about then?  Could something have got stuck in it?

[steve_earwig]

You're travelling through another dimension... Hold on, I'm sure I have a picture I made for weird Pug issues, it's here somewhere...

 

Exhaust manifold cracked, then filled up with soot? I think you'd notice if the exhaust was blocked by it being down on power. Maybe.

[OwdChina]

Probably exhaust manifold stud snapped. When the manifold warms up it expands and 90% of the noise goes. If it

sounds like TICK TICK TICK it's manifold leak.

[alf892]

Crack which closes up when hot......

 

Other sorts of cracks are available

[Bren]

Sounds like it is cracked - expansion closing the crack.

[carlo]

I suppose it can suddenly go then?  If it does this every time it's cold presume that may confirm it.  Sounds expensive, will try again later.

 

Yup, just tried it again cold - dreadful racket which I presume would quieten down again if I left it.  Oh balls, that will teach me to post here yesterday saying how reliable it had been

[steve_earwig]

Not sure what yours is but I know PSA TU engines are pretty good at cracking manifolds, mate of mine here sawed his up with an angle grinder and rewelded it with a mig, it's been like that 4 years now.

[OwdChina]

If it's that bad lift the bonnet and start it and have a look. You'll probably be able to see it......A little smoke.

[sierraman]

I had this once. The manifold was cracked, only about 2 inch. You could see the smoke when the engine was cold, getting the manifold welded up was fun. It's a real shitty job wherever exhausts are concerned, if its not completely rusted bolts etc its the ever present worry of the manifold studs shearing. I've got the flexi to do on the Focus soon, for what it's worth I'll get it done by local spanner man. Using an angle grinder inches from my face laid in the floor isn't my idea of fun.

[Andrew353w]

It'd be interesting to see of the noise or tone changes if you move off in reverse, as the manifold would be twisted the OTHER way and if the noise does change it'd suggest even more strongly that the manifold is damaged. If you do replace it I'd suggest changing the engine mounts at the same time, as it's the twisting action of the motor that can break the manifold; new mounts would reduce the rocking action of the motor. I know, my Xantia had this problem!