Knocking Exhaust

[Pob 1]

Hi,

 

I've got a Mongoose exhaust system fitted with a standard downpipe. Its knocks when I release the accelerator, so when coming up to junctions etc. Its knocking on the bulk head on the seam... Any ideas why this might be happening? The downpipe has been hit on the ground at some point and got a bit of a flat in it, Could this of bent it causing it to knock? I had it off yesterday and replaced the gasket and fixings at the manifold but it still knocking. It also sounds a bit blowy around that area, could this be the dent that is causing it? I've felt around it and its not got a hole, just sounds like it.

 

Finally in the exhaust fixing kit, do you use the shorter or longer bolts, do the springs sit onto downpipe flange... It had two gasket type washers in the pack.. what are these for?

 

Many Thanks,

Dan

[Rom 0]

How worn are your mounts ? If theres a lot of movement the surgeing forwards / backwards could be allowing the engine to move and knock the pipe.

 

Use whichever bolts fit best, there normally a bit fiddly to get on,mine only just reach, but are fine once started.

Iirc, the washers go in the hole before the bolt slides down. Then the spring and cap goes on from underneath, with the little nut.

They can be quite hard to get a good seal on. And also manifolds arent unknown to crack, which could be the blowing noise.

 

 

Its been a while since ive had mine off

[Pob 1]

How worn are your mounts ? If theres a lot of movement the surgeing forwards / backwards could be allowing the engine to move and knock the pipe.

 

Use whichever bolts fit best, there normally a bit fiddly to get on,mine only just reach, but are fine once started.

Iirc, the washers go in the hole before the bolt slides down. Then the spring and cap goes on from underneath, with the little nut.

They can be quite hard to get a good seal on. And also manifolds arent unknown to crack, which could be the blowing noise.

Its been a while since ive had mine off

 

Thanks for the reply,

 

I replaced the bottom mount with a second hand mount... Not brilliant I know but the one removed was split. The manifold has been welded (Gas welded) new manifold gasket fitted aswell.

 

Between the downpipe and bulk head there is about 1cm gap is this right? Could the downpipe be pushed too far into the middle section causing the downpipe to be pulled to close to the bulk head?

 

Many Thanks,

Dan

[Rom 0]

Its possible. Best thing would be to refit it all, see if thats the case.

 

Mines an Mi, so close is my middle name But i get no knocking with Group N mounts.

If the pipe is too far in the centre section, it will be making it harder to seal, as the angle will be off.

[Pob 1]

Its possible. Best thing would be to refit it all, see if thats the case.

 

Mines an Mi, so close is my middle name But i get no knocking with Group N mounts.

If the pipe is too far in the centre section, it will be making it harder to seal, as the angle will be off.

 

Thanks, I'll refit it like you say... On start up I can smell fumes being brought in by the fan, so something is leaking.

 

Thanks again,

Dan

[Pob 1]

Thanks, I'll refit it like you say... On start up I can smell fumes being brought in by the fan, so something is leaking.

 

Thanks again,

Dan

 

Hi,

 

I refitted the exhaust today, I have more clearance on the front pipe and it fits alot better now and doesnt blow from the middle section... Problem is, it still has the knocking I can hear it, but I can't see it. Its not the exhaust that is knocking, You can hear it constantly if you listen to the floor pan of the car. Its doing my head in, I can't see anything round the bulk head area that could be causing it... Any ideas?

 

Thanks,

Dan

[Guest Eurotrash]

you say its only on acclerating and letting off are you sure it isn't a mount? Cas mines doing the same and im pretty sure its a mount have been known to be well off before tho . Sorry to bring it down to noob langauge but is it almost like a "donk" on let off?

 

 

Think i may have miss read something ignore me

Edited December 4, 2007 by Eurotrash

[pug_ham 240 3 Cars]

Once before when a friends 205 had a random knock, usually when coming off the gas, it was the front end of the backbox hitting the beam / torsion bar due to movement.

 

A slight adjustment on the back box clamp & mounts sorted it.

 

Graham.

[Pob 1]

Once before when a friends 205 had a random knock, usually when coming off the gas, it was the front end of the backbox hitting the beam / torsion bar due to movement.

 

A slight adjustment on the back box clamp & mounts sorted it.

 

Graham.

 

Thanks for the replies.

 

Even at idle you can hear it, its coming somewhere from the front end. It really hard to pin point it due to the noise traveling through the chassis. As far as I can make out, its coming from the front drivers side. At idle is a faint tapping, easing off the accelerator is a knock. I think its the same knock when you pull off in first, drive me nuts now

 

Dan

Edited December 4, 2007 by Pob

[Guest Eurotrash]

Turn up the radio knocking goes away thi is what i like to call the quick fix method

[Pob 1]

Turn up the radio knocking goes away thi is what i like to call the quick fix method

 

 

Fixed it! I replaced the rear engine mount bush as the one I fitted was second hand. When I removed it I noticed the bracket on the subframe was loose with movement which caused a metal knocking noise. Removed the bracket and found the bolt had worn causing play in the bush, Replaced the bolt and fixed the knocking

 

Thanks for all the advice

Dan