Knock when coming off accelerator

[Patrick Bateman]

Most notable at lower speeds and in 2nd/3rd, don't have to accelerate hard, just slightly and when I come off the pedal there's a very slight delay (<1s) then a light knock that appears to be from the front right.

Engine mounts and gearbox mounts are all pretty new.

 

[STEVE.M]

BMW or Clio?
@Patrick Bateman

 

[Patrick Bateman]

Clio, no M5 any more sadly!

 

[STEVE.M]

Clio, no M5 any more sadly!

172/182?
To eliminate the engine mounts, have an assistant load up the transmission with the brakes applied, and observe any movement or noises.
And make sure the wheels are done up tight too.

 

[Patrick Bateman]

182 Trophy.

Wheels seem to be good anyway.

 

[Patrick Bateman]

Haven't got it in the garage yet but I did notice the sound as I switched off the engine the other day so that screams engine mount to me.

They were replaced last year so could it just be a case of them needing moved/realigned somewhat?

 

[STEVE.M]

Haven't got it in the garage yet but I did notice the sound as I switched off the engine the other day so that screams engine mount to me.

They were replaced last year so could it just be a case of them needing moved/realigned somewhat?

:smile:
I`ll sleep on it.

 

[Patrick Bateman]

:smile:
I`ll sleep on it.

Any thoughts then?

 

[STEVE.M]

Any thoughts then?

Back to post 4.

 

[Patrick Bateman]

Garage found a tie road had a decent amount of play in it but replacing it hasn't stopped the knock. They couldn't find anything else.

Is there a chance a shagged top mount could be the culprit? Looks like my sachs dampers are needing refurbed so when they come off I'll be able to see.

Edit: or could it be the damper itself given it's the right one that's weeping?

 

[Coops Mk1]

could well be knocking shocker tbh, get that sorted first before digging any deeper

 

[Patrick Bateman]

Maybe a case of not seeing the forest for the trees, just never thought a shock could make such a knock unless it was going over bumps.

I've got a spare cup set I'll swap to anyway while the sachs are off so it'll be easy to find out anyway. Cheers.

 

[cs_dave]

Dog bone mount?

 

[Patrick Bateman]

Mmm well they said they couldn't find anything else and they agreed the sound seemed to be from the front right. Both engine mounts themselves were replaced less than 8k miles ago with Renault parts.

I'll keep the dogbone in mind though if it isn't the shock or top mount. Previous owner put powerflex bushes in it as far as I can remember.

 

[Patrick Bateman]

Shocks changed but it seems this is none of the usual culprits and is actually a problem with the exhaust. The flange where the exhaust manifold joins the cat is knackered and some of the pipework itself just up from that, mechanic says something there seems to be hitting off the anti-roll bar and it'll be a pain in the backside to fix too so hopefully going to go to an exhaust specialist/fabricator fairly nearby.

Anyone else had issues in this area?

A bit miffed as the other garage I've used for a few years now had just sorted this and never noticed anything-

 

[Ads29]

Generally play in the engine/gearbox mounts causes the exhaust to hit off the subframe and anti roll bar

 

[ForceIndia]

Does it happen at slow speeds, when manoeuvring? Ball joint?

 

[Patrick Bateman]

I think the exhaust is the culprit to be fair, there's a bodged weld holding on part of it I'm told and two different garages have looked over all the mounts and suspension components.

One of the guys who looked at it is a current workmate who was just giving his old boss a help, I know first hand he's a good mechanic.

Along with the fact that the dogbone is polybushed, the two engine mounts have done 7k miles, both wishbones have done 14k miles and it's just had a tie rod.

 

[Crybert]

From your initial post it sounds like the mount under the battery tray. It's a completely free fix. Whip out the battery and tighten it up

 

[chris blue]

I had a real big knocking on deceleration recently, (Another thread) and at the time it happened i found a 7cm bolt lying in the road
Turned out to be the dogbone

If that bolt was loose, it may cause just a small amount of knocking, as I am getting a tiny bit again now
So its back up on the axle stands for me

Do dogbone mount bolts always loosen themselves?

 

[Patrick Bateman]

So the exhaust is now sorted and the knock is still there.

Revisiting engine and gearbox mounts, is it possible for them to look good but actually be suspect enough to cause this?

 

[Mr Plums]

Change the dogbone mount mate, remove the bushes and replace with powerflex ones, i bet it cures it.

 

[Patrick Bateman]

The dogbone mount already has powerflex bushes, just don't know how old as the previous owner fitted them.

 

[Mr Plums]

The dogbone mount already has powerflex bushes, just don't know how old as the previous owner fitted them.

What colour are they?

 

[Patrick Bateman]

Purple AFAIK. I still have the boxes they came in that he gave with the car.

 

[chris blue]

check all the bolts on the dogbone- one of mine worked loose and fell out
does sound like dogbone issue tbh

(My bushes on dogbone yellow- theres a photo on here somewhere)

 

[Patrick Bateman]

I'll prioritise that then, especially given I had the other two mounts replaced previously and didn't touch the dogbone because it was already polybushed.

At least I've had the cat flange replaced and sorted this way...

 

[Crybert]

Take out the battery. My problem was 99% like yours and turned out it just needed tightened (the engine mount under the battery). Takes 10 mins max

 

[Patrick Bateman]

Have removed the battery and that mount is tight.

If it's not the dogbone I'll be at my wits' end.

 

[bozothenutter]

is the bolt under the battery still in one piece?
mine had sheared below the mount, so everything looked fine....just made it knock.
it is the one coming from the tripod mount on the gearbox

 

[Patrick Bateman]

Well all the nuts are solid so I've no reason to suspect anything untoward.

I'd have been a bit miffed if something was up given it's not very old.

 

[Patrick Bateman]

Mechanic has checked the dogbone (already powerflexed) and gone round the suspension components checking for anything loose and can't find s**t.

Perhaps it isn't the exhaust hitting off the anti-roll bar? I've found a thread from 2008 where a chap describes the exact same issue and it turns out to be the carbon canister-

http://www.cliosport.net/threads/knocking-when-taking-foot-off-the-gas-in-1st-and-2nd-gear.137779/

How would that work exactly? I've had a ticking on hot idle for absolutely ages and most folk reckoned that could be the carbon canister, can it degrade in such a way as to cause a knock or become loose enough?