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Exhaust rattle/ knock

dazzawest

dazzawest

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1,101
Driving home tonight down the motorway car was fine, then started raining pretty heavy, a lot of standing water and what sounded like the exhaust started to knock pretty loudly. Loud enough for me to think it might be hanging off hitting the road. Pulled off into services all seemed ok, steady drive home didn't do it again.

when I got back I jacked the car up and had a quick look and all seems ok.

now I've had a quick search around and found a couple of threads suggesting its the exhaust and the rain that's the cause and a couple of people seem to suggest new exhaust rubbers and gearbox mount inserts should cure it.

So questions are, a; has anyone else had this issue? Know the cause? Or fixed it? And b; where can I get uprated exhaust rubbers? The only place I've found so far is sumo power who sell j's racing ones. Powerflex don't seem to sell them, any other suggestions.

thanks for reading and apologies for such a long post, also I've got a HKS hi power 409 fitted.
 
Fairly common with aftermarket systems.

I had the same with my Supersprint b pipe and back box.
 
Yeah mine did this, bricked it when I first heard it. It is common. There are two theories (That I know of):

1. Cold rain water hitting a hot exhaust causing steam, the steam has no where to go causing pressure between the exhaust and underside of the car. This causes the exhaust to 'vibrate' if you know what I mean, once the water has boiled away it goes away as no more steam, no more pressure.

2. The exhaust expands and detracts when hot/cold etc causing it to, again, 'vibrate'. When cold water hits a hot exhaust this causes the exhaust to expand/detract.

The place who put my exhaust on gave it more clearance (I think). He was reluctant to share what he actually did but it hasn't fully cured the problem but it is a 100% better. Hope this helps.
 
cool, interesting couple of theories, second probaly sound a bit more plausible. i'll get it on the ramp and have a look.

drove it today in the dry no noise so pretty sure this is noise im hearing.

Any ideas where to get exhaust mounts from?
 
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