P38A excessively noisy exhaust

kermit_rr · Oct 11, 2020

Ok i think I'm having a mental block here, for ages i thought all the noise was coming from the middle box as it's been leaking for ages.
Finally got round to replacing it and fired up expecting range rover quiet burble, but not really much difference.
I've stuffed rags up the tail pipes to try and isolate any leak in the system but can't find any leak anywhere. At idle it sounds pretty good, but hit the throttle and it's like the exhaust manifold are blowing at the gaskets, but I'm pretty sure they aren't.
Noise is definitely from the front half of the system.
I'm obviously being stupid as usual!! What am i missing?

Mark Piercy · Oct 11, 2020

Did you do the revving up with the tail pipes blocked as well?

kermit_rr · Oct 11, 2020

I did

Mark Piercy · Oct 11, 2020

Next thing is to let it run blocked and go around the manifolds and work your way back along the system... Poopy job but it should reveal you dilemma my good man?!

kermit_rr · Oct 11, 2020

It's kinda hard revving the engine while underneath lol

Henry_b · Oct 11, 2020

I bet you my left nut it is the manifolds or a leak at where the mani connects to the downpipes/cats

kermit_rr · Oct 11, 2020

It does sound like manifolds but when i rev it with my head under the bonnet, you only hear normal engine noise

Henry_b · Oct 11, 2020

kermit_rr said:
It does sound like manifolds but when i rev it with my head under the bonnet, you only hear normal engine noise

Get yer other half to dance on the skinny pedal while you scoot around underneath

kermit_rr · Oct 11, 2020

Henry_b said:
Get yer other half to dance on the skinny pedal while you scoot around underneath

That's a big assumption right there

Henry_b · Oct 11, 2020

kermit_rr said:
That's a big assumption right there

Process of elimination..

Check the rear intermediate pipes, if they're fine move on to the centre muffler and then the downpipes and then the manifolds etc etc

A fast idle stick works wonders,

kermit_rr · Oct 11, 2020

I'm certain is North of the middle box, I'll have another looksee tomorrow. I thought sustained high revs were a box killer?

Henry_b · Oct 11, 2020

kermit_rr said:
I'm certain is North of the middle box, I'll have another looksee tomorrow. I thought sustained high revs were a box killer?

Holding it at 5 grand in neutral or park wouldn't do it any good.

You're looking to only raise the idle up to around 1800rpm.

Grrrrrr · Oct 12, 2020

kermit_rr said:
It does sound like manifolds but when i rev it with my head under the bonnet, you only hear normal engine noise

Strip of bog paper on a stick and see where it flutters?

kermit_rr · Oct 12, 2020

Grrrrrr said:
Strip of bog paper on a stick and see where it flutters?

You mean take the serp belt off first?

Marshall8hp · Oct 13, 2020

Or the fan as a better alternative, then you at least have a water pump running.

Mark Piercy · Oct 13, 2020

Or have someone carefully stop the viscous fan while you investigate, inspector.

kermit_rr · Oct 13, 2020

Mark Piercy said:
Or have someone carefully stop the viscous fan while you investigate, inspector.

Carefully!?

Mark Piercy · Oct 13, 2020

kermit_rr said:
Carefully!?

Blindly....

tomcat59alan · Oct 13, 2020

Grrrrrr said:
Strip of bog paper on a stick and see where it flutters?

In the pan?

tomcat59alan · Oct 13, 2020

Mark Piercy said:
Blindly....

Fingerlessly.

P38A excessively noisy exhaust

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Think outside, no box required.

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Think outside, no box required.

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Think outside, no box required.

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Think outside, no box required.

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