Technical knocking noise from underneath car - any ideas?

[peter_miles_01]

getting a knocking noise (almost like exhaust hitting roof of floor pan) when i back off from throttle or go over crests in road.

obviously somthing is loose but ive wiggled the exhaust and its not the back box? - could be centre section i suppose?

has anyone else had this with their puntos?

 

[bredsticz]

Get underneath and wiggle the whole exhaust system, bit by bit.
Don't be afraid to use a bit of force either.
See if anything else is loose while under there. Maybe your heat shields are loose?

 

[DaveMcT]

On mine the mid box mount was banging on the tunnel. I put some small jubillee clips on the pegs to stop the rubber hanger from sliding too far.

 

[peter_miles_01]

thats where it sounds like its coming from - the tunnel.

 

[bredsticz]

Most likely that centre pipe then, if not between the floor and the pipe are heat shields, if they are loose it will cause a rattle

 

[HGTCraig]

Had similiar problem just two weeks ago, turned out that the bracket holding the centre pipe (Just near 2nd cat) had broken. Left it to late to fix and ended up having to replace both centre pipe + backbox to the tune of £500

Hope you track down the culprit soon

 

[bredsticz]

Had similiar problem just two weeks ago, turned out that the bracket holding the centre pipe (Just near 2nd cat) had broken. Left it to late to fix and ended up having to replace both centre pipe + backbox to the tune of £500

Hope you track down the culprit soon

Why did you have to replace them? I had someone from work who's backbox rusted and snapped away from the centre pipe, instead of replacing she had the rust cleaned off and welded back together for £25

 

[HGTCraig]

Why did you have to replace them?

Upon taking it to the nearest Kwik-fit garage one saturday after the bracket completely gave way and it was dragging on almost every bump on the road. Kwik-fit cleverly must have mis-judged how low it was hanging and when they rang to update me on cost, fault etc.. they told me it had snapped completely and was off on the floor!

Although I could not prove it I think they got it caught on the ramp and ripped it off being aggresive driving it on the ramp!! Angry and frustrated I drove away from there with a few exchange of words.

 

[steveydb]

This is exactly what im trying to find out at the moment. Completed a 1.4i Turbo conversion and swapped over the rear beam. I have new Spax Suspension all round and new bushes, but there is a knock coming from the rear. Taken a look at it today, pushed it from side to side, jumped up on it to make it go up and down, but for the love of god I cant seem to replicate the noise I hear when im driving it. Tightened up all bolts to ensure theres no play but still got this blasted knocking noise.

 

[bredsticz]

This is exactly what im trying to find out at the moment. Completed a 1.4i Turbo conversion and swapped over the rear beam. I have new Spax Suspension all round and new bushes, but there is a knock coming from the rear. Taken a look at it today, pushed it from side to side, jumped up on it to make it go up and down, but for the love of god I cant seem to replicate the noise I hear when im driving it. Tightened up all bolts to ensure theres no play but still got this blasted knocking noise.

Yours only sound when you are driving? Try jacking a rear wheel up and see if it does it just when the wheel is spinning

 

[DaveMcT]

The cause of my rattle wasnt easily seen from underneath it was engine movement that made the end of the mounting peg hit the tunnel. 50p worth of jubillee clips stopped it moving so far to the right and problem solved.