Exhaust knocking

[Connor-J]

I’ve got an annoying knocking noise coming from my exhaust. Recently installed a scorpion cat back system and ever since I’ve had the knocking noise but it only knocks after you’ve been driving it hard for a while and goes away after driving civilised for a bit. I’ve had a look under today and slightly bent some of the heat shield in the areas that were close. Still hasn’t sorted the problem. Almost sounds like the exhaust is knocking against the underside of the car. Does anyone know what may be causing the knocking? Thanks!

 

[CaptainCaveman]

Does anyone know what may be causing the knocking? Thanks!

Likely to be the tips knocking against the diffuser?

 

[Connor-J]

Likely to be the tips knocking against the diffuser?

Could well be,anyway you know to solve this?

On the other hand though it does sound like it’s knocking on the underside of the car, doesn’t sound ‘tinny’ as I’d imagine the tips knocking would, but I may be wrong?

 

[adrianu84]

I’ve got an annoying knocking noise coming from my exhaust. Recently installed a scorpion cat back system and ever since I’ve had the knocking noise but it only knocks after you’ve been driving it hard for a while and goes away after driving civilised for a bit. I’ve had a look under today and slightly bent some of the heat shield in the areas that were close. Still hasn’t sorted the problem. Almost sounds like the exhaust is knocking against the underside of the car. Does anyone know what may be causing the knocking? Thanks!

I have the exact same problem lol , it been bugging me .
I too have bought the scorpion cat back.
I too thought it was the tips so I tuck them off and drove it and it still did it, so it wasn't the tips.
I'm still in the process of fixing it the problem.
I think it's the the upright bracket that supports the catback , it seems to sit very close to the cars bodywork under the bumper.


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[Connor-J]

I have the exact same problem lol , it been bugging me .
I too have bought the scorpion cat back.
I too thought it was the tips so I tuck them off and drove it and it still did it, so it wasn't the tips.
I'm still in the process of fixing it the problem.
I think it's the the upright bracket that supports the catback , it seems to sit very close to the cars bodywork under the bumper.


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That’s good to know then, yes I was thinking it must be something around that area as it sounds like the knocking is coming from the boot floor area under the car.

 

[adrianu84]

That’s good to know then, yes I was thinking it must be something around that area as it sounds like the knocking is coming from the boot floor area under the car.

I'm going to have a proper look next weekend and will let you know if it's that.
I think the exhaust bracket may need bending a little away from the car frame or putting some rubber washers around it to hold it off , if that makes sense.
I was thinking about emailing scorpion and seeing what they have to say.

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[Connor-J]

I'm going to have a proper look next weekend and will let you know if it's that.
I think the exhaust bracket may need bending a little away from the car frame or putting some rubber washers around it to hold it off , if that makes sense.
I was thinking about emailing scorpion and seeing what they have to say.

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Ahh right okay thanks! Yes that makes sense I did think about putting some washers between the bracket and the chassis to drop the level of the mounts slightly but thought this may then impact on the alignment of the tail pipes in the holes and they may start knocking then?

The installation piece of paper did say about possibly modifying the brackets but didn’t say how and why you’d need to so I ignored it as it seemed to all fit fine.

 

[adrianu84]

Ahh right okay thanks! Yes that makes sense I did think about putting some washers between the bracket and the chassis to drop the level of the mounts slightly but thought this may then impact on the alignment of the tail pipes in the holes and they may start knocking then?

The installation piece of paper did say about possibly modifying the brackets but didn’t say how and why you’d need to so I ignored it as it seemed to all fit fine.

I think as long as you can hold bracket of enough to stop it touching the frame I think everything else will line up ok.


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[lewishunter98]

My ktec had the issue of knocking on the rear beam

Then I found out one of the tips was also hitting on a bit of the bodywork dropping down underneath the boot flood/behind the diffuser. I could literally shake it and make it knock with my hand.

But I had the exact same thing, only knocked when I went fast ISH. Stopped when I calmed down [emoji23]

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[Connor-J]

My ktec had the issue of knocking on the rear beam

Then I found out one of the tips was also hitting on a bit of the bodywork dropping down underneath the boot flood/behind the diffuser. I could literally shake it and make it knock with my hand.

But I had the exact same thing, only knocked when I went fast ISH. Stopped when I calmed down [emoji23]

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I’ll have to have to try and have a look under without it jacked up as the rear will sit lower down jacked up and see. I did give it a shake for knocking but only around the rear beam so maybe have to try the back box and see f the tail pipes are knocking too, thanks! Yeah can’t drive slow all the time haha!

 

[turkie172]

You will find as the exhaust gets hot like you say when you push on the heat expands and the exhaust gets longer a prime place is over the rear axle and if you jack the car up the axle moves away and the clearance looks fine go by the mount nearest the mid section and see how central it looks to get an idea how far forward or backward the exhaust is. Also if the engine is rocking on bad mounts the manifold acts as a big lever to the rest of the exhaust system.

 

[Connor-J]

You will find as the exhaust gets hot like you say when you push on the heat expands and the exhaust gets longer a prime place is over the rear axle and if you jack the car up the axle moves away and the clearance looks fine go by the mount nearest the mid section and see how central it looks to get an idea how far forward or backward the exhaust is. Also if the engine is rocking on bad mounts the manifold acts as a big lever to the rest of the exhaust system.

I think I’m going to try and see the clearance when it’s not jacked up if I can. And I’ll check the position of the centre mount, thanks!

 

[adrianu84]

I think I’m going to try and see the clearance when it’s not jacked up if I can. And I’ll check the position of the centre mount, thanks!

Just had my exhaust sorted by DDC at Doncaster , it just wasn't sat right and need to be pushed on more , if that helps you out.

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[CM200]

I’ve got an annoying knocking noise coming from my exhaust. Recently installed a scorpion cat back system and ever since I’ve had the knocking noise but it only knocks after you’ve been driving it hard for a while and goes away after driving civilised for a bit. I’ve had a look under today and slightly bent some of the heat shield in the areas that were close. Still hasn’t sorted the problem. Almost sounds like the exhaust is knocking against the underside of the car. Does anyone know what may be causing the knocking? Thanks!

Can confirm that on myn it’s the tip of one of the exit pipes tapping against the heat shield in the rear diffuser ports.

Only does it once the exhaust is warmed up and only at 2.3-3.5k revs for me. Might not be the same issue for everyone but gonna have to fiddle with it tried wrapping it in heat tape temporarily and it just wears away -_-‘.