Technical Center exhaust silencer knocking on chassis

[W Bakker]

Hi all,

I have just figured out what causes the loud knocking sound coming from my car going over steep speed bumps and cobblestone streets. The middle silencer seems to be off-centred, causing it to hit the right side of the tunnel it's supposed to fit inside. The silencer was replaced last year at roughly the same time the knocking started, garage that carried out the work is currently closed and won't be back until September. I'd like to fix it myself before then because it's driving me nuts! Does anybody know if it's possible to adjust the silencer, or does it need to be replaced for a better fitting example?

 

[The Panda Nut]

You are right its not on straight. Any Exhaust Centre or decent garage should be able to adjust itin half an hour os so. I wonder why its off though. The front end of the centre section needs to be checked as well. and also the front pipe bracket to the gerbox needs to be checked to make sure its all properly fixed and in line.

It can be fixed and shouldn't need replacing it looks in great condition still.

 

[Jockstrap]

I've the same vehicle.

Check the rubber hangers at each side of the back box. If the outer is missing or shot is could be pulling the exhaust inward.

Here's a photo of mine. Shows the centre hanger near vertical.

 

[Jockstrap]

Had another look at the OP photo. The hanger hook is shiny. Looks like the rubber has shifted.

 

[Ralf S.]

I think the curve of the pipe is just too close to the fuel tank.. either it's a not 100% accurate copy of the standard silencer or it needs to be fitted further forwards, to take the curve away from the body.

Having said that, the Younger Mrs S. had a Cinquecento where moving the silencer forwards (shoving the pipe further over/into the header) gave more clearance between the front part of the bend and the fuel tank.. but caused knocking from the rear part of the bend instead... so that was just a bad (very cheap though) silencer.

If moving the front away from the body brings the rear of the bend into contact, then you need a new silencer.. but if you can increase the clearance just by fitting the pipe 2 or 3 cm further forward, then it's cool.

Also... the rubbers get tired, so wind a cable tie around yours and squeeze it in a bit.. it'll prevent so much movement around the hanger.


Ralf S.

 

[John202020]

The rubber hanger looks pulled towards the rear rather than straight down?
I had issues with my very cheap( £95 for center and back box) exhaust knocking, I sorted it by using a piece of rubber hanger, cable tied in place to push it sideways, think its still there as there's no sound years later, in fact it's lasting very well given the price

 

[steveras57]

The rubber hanger looks pulled towards the rear rather than straight down?
I had issues with my very cheap( £95 for center and back box) exhaust knocking, I sorted it by using a piece of rubber hanger, cable tied in place to push it sideways, think its still there as there's no sound years later, in fact it's lasting very well given the price

I had a similar issue on mine -near the rubber hanger closest to the back box the two stubs that the rubber connects to were not quite aligned (think the one one the "cheepo " exhaust was not welded in quite the right position!) this pulled the pipe to close to the hangers and on startup (when the engine shakes on the mountings) the pipe used to clang against the end of the chassis mounted hanger(also used to happen on occasion on very bumpy roads or if i was "ham-footed" with the clutch causing the engine to "judder" on its rubber mountings!.
Solved it by putting a rubber grommet over the end of the chassis hanger so the was metal to rubber rather than metal to metal contact!
been quiet since!.

 

[GettinBetter]

IMO, the problem starts back further.
Is it possible the user has reversed back into something only the tailpipes would hit? and distort the two rear previously correct bends.

The exhaust has previously been in the correct place as shown by the shiny underside of the bracket.

 

[John202020]

It's also possible the front section is too long pushing everything too far back? But the hanger welded in the wrong place is much more understandable

 

[W Bakker]

Hi everyone, thanks so much for all the replies! I lay down next to the car, gave the exhaust a few solid kicks, and the noise disappeared. It looks like the exhaust shifted about 2–3 cm to the left and now clears the tunnel it was previously knocking against. I think I’ll leave it as is for now. If the noise comes back, I’ll take it in and have it fixed properly.

 

[jackwhoo]

Repair by kicking....
Kicking it better...

 

[steveras57]

No harm in putting the boot in as long as its accurate!