Boxster 3.2 S Issue - exhaust blow?

[geraintthomas]

I've posted in other forums, so I thought I'd throw a thread in here too.

I'm getting this horrible, loud, spluttery rattling sound coming from the rear left of the car after the car's been driven quite heavily. If I drive the car carefully with low revs, even on the motorway, it's fine. If I push the car hard with the engine a little below running temperatures, it's fine. However, when the car's at running temperature and I start to drive heavy, this spluttering rattling starts to happen. If I start to drive calmly after it, it'll start to go away again. And so on.

There is no loss of power, no error codes, nothing. I thought it was bad sparks or coils but I've tested another set with no results. It sounds more like an exhaust blow.

Here's the videos:

Inside the car:

https://www.youtube.com/watch?v=i69lltfykW8

Outside the car:

https://youtu.be/tyKCsiF_RJo

But like I said, it only happens after the car's been warmed up and after driving hard. It'll go away or won't happen at all if I drive it carefully. It sounds like it's coming from the N/S rear.

Could this be a failed cat? With the insides rattling when it heats up?

Some advice please! Many thanks :)

Edited January 8, 2016 by geraintthomas

[Ahsai]

Sounds like exhaust heat shields or internals of cats/mufflers or exhaust brackets. You need to jack up the car and use a mechanic's stethoscope to probe around to pinpoint the source of the noise, maybe with engine revving.

Edited January 8, 2016 by Ahsai

[geraintthomas]

Sounds like exhaust heat shields or internals of cats/mufflers or exhaust brackets. You need to jack up the car and use a mechanic's stethoscope to probe around to pinpoint the source of the noise, maybe with engine revving.

Unfortunately I can't. It doesn't do it on cold, and if I heat it up enough to do it, it'll be far too hot to touch.

Just updated the videos as they were the same.

Edited January 8, 2016 by geraintthomas

[Ahsai]

Hot is ok. You touch the components with the stethoscope's long metal probe.

 

http://www.amazon.com/Lisle-52500-Mechanics-Stethoscope/dp/B0002SQYSM

[geraintthomas]

Thanks!

But you think it's definitely exhaust related coming from that video? Luckily I have a friend who will lend me a cat to try it to rule it out.

[Ahsai]

No, I cannot be 100% sure hence my suggestion of the proper tool to give you a definitive answer (as opposed to people guessing on the internet, including me).

 

Checking with the stethoscope is a lot less work than swapping out the cat(s) anyway.

[geraintthomas]

Understandable, I'll order one asap. Thanks for the help!

Edited January 8, 2016 by geraintthomas

[JFP in PA]

If you had bad cats, the car would be coding.

 

You have an exhaust leak.

[geraintthomas]

That only happens while hot?

[JFP in PA]

That only happens while hot?

 

Sure, why not?  Header flanges or other joints may only open up when the system is hot.

[geraintthomas]

Very good shout. It'll be hard to diagnose as I'll have to dive into an exhaust garage and ask them to check it immediately while it's still hot...

[geraintthomas]

But then, it does sound like it rattles as well as splutters. That's what made me think of the internals of a cat.

But you're 100% certain that it would always throw up a code if the cat was at fault?

[JFP in PA]

But then, it does sound like it rattles as well as splutters. That's what made me think of the internals of a cat.

But you're 100% certain that it would always throw up a code if the cat was at fault?

 

If the cats were sufficiently dead that they rattled , you would be getting codes for the cats being below minimum conversion rates, believe me.  We see it regularly.  Your leak may also be hitting a heat shield, like Ahsai mentioned.  You need to get the car up in the air and start tracing the system to see where it is.

[geraintthomas]

Shall do.

What do you mean by the leak hitting the heat shield? I had a quick look under the car and couldn't see any heat shields over the cats. There's heat resistant material under the rear bumper but nothing directly over the cats.

[JFP in PA]

Shall do.

What do you mean by the leak hitting the heat shield? I had a quick look under the car and couldn't see any heat shields over the cats. There's heat resistant material under the rear bumper but nothing directly over the cats.

 

There should be heat shields above sections of the exhaust, which may not be entirely visible with out the car on a lift.  As these shields are relatively close to the exhaust system, a leak could be coming out and blasting against the shield, which can make a rattle like sound.  You can see several of them (quilted looking metal) in these photos:

 

 

 

Again, you need to get this car up in the air and have a detailed look.

[geraintthomas]

Ah okay.

It'll be quite hard to diagnose as it only happens after a hard drive and cools after a short while of stopping. They'll have to catch it while it's still hot.

[JFP in PA]

Ah okay.

It'll be quite hard to diagnose as it only happens after a hard drive and cools after a short while of stopping. They'll have to catch it while it's still hot.

 

Then take it out and drive it like you stole it, them put it on a lift.

[geraintthomas]

That's the kind of advice I like to hear.

[geraintthomas]

SOLVED.

 

Took it to an exhaust garage and they spotted the problem instantly. The join where the headers join the exhaust has a gasket which is ruined, and is hanging from one of the bolts. You could feel the blow straight away from it, and the rattling is the gasket rattling around hanging by a thread.

 

He's ordering a new part for me and, when I asked how much the whole job would be to fix, he quoted:

 

"Ohh I don't know, I mean you're talking around... £30?"

 

£30! To fix the problem! Dreaming :D

 

Thanks for the help though guys, much appreciated.

[Ahsai]

John nailed it :) Glad to hear it's a cheap and easy fix.

[JFP in PA]

John nailed it :) Glad to hear it's a cheap and easy fix.

 

Even a blind squirrel finds an acorn once in a while..................  Glad you got it sorted.

[Ahsai]

 

John nailed it :) Glad to hear it's a cheap and easy fix.

 

Even a blind squirrel finds an acorn once in a while..................  Glad you got it sorted.

 

 

You're too modest. Experience shows :)