Diagnosing knocking up front...

K

Kennedy

A2OC Donor
After replacing a few worn and tired parts up front on my wife's TDI it still seems to have a very audible knocking sound when driving it. The knocking is particularly noticeable on bumpy roads (as you would expect) mainly to front near side... the sound is also there when coasting so feels like it could be steering and suspension related but not sure.

Just fitted/replaced:

Meyle HD droplinks
Meyle anti-rollbar bushes
New anti-rollbar brackets + bolts
Track rod ends both sides

...there doesn't appear to be any noticeable movement at inner tie rod.

What else is a common cause of knocking up front, any idea what I should be checking next? - appreciate anyones thoughts.

Kennedy.
 
Kennedy said:
What else is a common cause of knocking up front, any idea what I should be checking next?
Click to expand...

I'd be looking at the wishbones, the bushes they sit in, and the top mounts (which I suspect are the source of your 'knocking'). The front springs and shocks also need checking.
 
Strut Upper Bearings maybe ? You don’t have to replace the whole Mountings. The Bearings were available separately last time I looked.

Steve U
 
Since you've eliminated the obvious ones I always mention, how about gearbox mounts / dog bone? Secondly, are the bonnet catches at the rear corners of the bonnet sitting down completely immobile, or are they able to move? On one of ours, if you push the bonnet corner down firmly it is able to move slightly and makes a metallic click - I think some people have mentioned shimming this with thin plastic or rubber to prevent movement. We also get a clunk from the top of one strut under compression which probably needs the top nut tightening very slightly but it is difficult to get to behind the Webasto and brake reservoir.
 
A few tips:

1) As hinted above: remove bonnet, take for a brief drive (the car, not the bonnet). If noise has gone there are plenty of tips on here to get the bonnet back on sans rattles.

2) Pop the car into first, car running / clutch down / handbrake firmly on. 'Bump' or dab the clutch. Try same in reverse. If noise appears, it's either engine bottom mounts, other mounts or possibly driveshaft related. If it is making a noise, get someone to watch what's happening, just be sure not to get run over!

3) One of my cars had what appeared to be good wishbone bushes but actually the front wishbone bush washers had failed in an odd way, allowing for movement and noise under braking / acceleration. Try kicking the tyre at the top very hard, both backwards and then forwards (not in and out). Sometimes this can reveal the source of the noise.

4) For others reference, if you suspect anti-roll bar bushes, links or loose link bolts but really can't seem to get anywhere, in the past I've disconnected the links at the bottom and just run up the road like that (assuming you don't live on a twisty mountain pass it's pretty low risk). If sound still there, it's nothing to do with the anti-roll system.

5) (1 really as it's the easiest check) get someone to rock the car side to side as hard as they can: you can then listen out for the noise and carefully feel around as well, often you can feel exactly where the problem is. Similarly try bouncing the car up and down as hard as possible. In the past I've got the car a little off the ground with a trolley jack and released the jack very quickly, this'll sometimes reveal something normal bouncing won't.

My above wishbone bush issue took AGES to find as it was so weird. I actually machined up some extra thick washers and that was it: noise gone.

Overall there're not 'that' many parts to an A2's suspension so it's just a case of taking your time and being logical.

Good luck!
 
steve_c said:
I'd be looking at the wishbones, the bushes they sit in, and the top mounts (which I suspect are the source of your 'knocking'). The front springs and shocks also need checking.
Click to expand...

Thanks Steve, the suspension is definitely tired on this one and I don't like the way it sits on one corner at the back either...

if it is top mount/s then it might be the push I need to do suspension all round on it! I'll give the struts a good wrestle later and see if I can see/feel anything clunking about.
 
Robin_Cox said:
Since you've eliminated the obvious ones I always mention, how about gearbox mounts / dog bone? Secondly, are the bonnet catches at the rear corners of the bonnet sitting down completely immobile, or are they able to move? On one of ours, if you push the bonnet corner down firmly it is able to move slightly and makes a metallic click - I think some people have mentioned shimming this with thin plastic or rubber to prevent movement. We also get a clunk from the top of one strut under compression which probably needs the top nut tightening very slightly but it is difficult to get to behind the Webasto and brake reservoir.
Click to expand...

I didn't even think about the bonnet potentially being a source of knocking, but I'll be sure to check that later. With regards the top nut on the struts I know the access is very limited, I remember swearing quite a bit doing that corner on my TDI90 when my coilovers went on!... Thanks for comments.
 
Rusty911 said:
A few tips:

1) As hinted above: remove bonnet, take for a brief drive (the car, not the bonnet). If noise has gone there are plenty of tips on here to get the bonnet back on sans rattles.

2) Pop the car into first, car running / clutch down / handbrake firmly on. 'Bump' or dab the clutch. Try same in reverse. If noise appears, it's either engine bottom mounts, other mounts or possibly driveshaft related. If it is making a noise, get someone to watch what's happening, just be sure not to get run over!

3) One of my cars had what appeared to be good wishbone bushes but actually the front wishbone bush washers had failed in an odd way, allowing for movement and noise under braking / acceleration. Try kicking the tyre at the top very hard, both backwards and then forwards (not in and out). Sometimes this can reveal the source of the noise.

4) For others reference, if you suspect anti-roll bar bushes, links or loose link bolts but really can't seem to get anywhere, in the past I've disconnected the links at the bottom and just run up the road like that (assuming you don't live on a twisty mountain pass it's pretty low risk). If sound still there, it's nothing to do with the anti-roll system.

5) (1 really as it's the easiest check) get someone to rock the car side to side as hard as they can: you can then listen out for the noise and carefully feel around as well, often you can feel exactly where the problem is. Similarly try bouncing the car up and down as hard as possible. In the past I've got the car a little off the ground with a trolley jack and released the jack very quickly, this'll sometimes reveal something normal bouncing won't.

My above wishbone bush issue took AGES to find as it was so weird. I actually machined up some extra thick washers and that was it: noise gone.

Overall there're not 'that' many parts to an A2's suspension so it's just a case of taking your time and being logical.

Good luck!
Click to expand...

Nice one for the breakdown of points, a few easy things to try before I do anything too drastic. Point 2 I did try, putting in gear with handbrake on and dabbing clutch... I did it quite a few times and got just a couple of little knocks – but not every time... could be part of the problem so thanks for highlighting lower engine mounts as possible cause. Hopefully it's not the driveshafts.
 
Kennedy said:
Thanks for all comments, I appreciate the help. I'll feedback once I'm clearer on what it could be.
Click to expand...
Check fog lights are tight as these can rattle/knock if loose
Also worth checking wheel arch
liners are secure as above , both simple no cost checks.
 
Kennedy said:
After replacing a few worn and tired parts up front on my wife's TDI it still seems to have a very audible knocking sound when driving it. The knocking is particularly noticeable on bumpy roads (as you would expect) mainly to front near side... the sound is also there when coasting so feels like it could be steering and suspension related but not sure.

Just fitted/replaced:

Meyle HD droplinks
Meyle anti-rollbar bushes
New anti-rollbar brackets + bolts
Track rod ends both sides

...there doesn't appear to be any noticeable movement at inner tie rod.

What else is a common cause of knocking up front, any idea what I should be checking next? - appreciate anyones thoughts.

Kennedy.
Click to expand...
Having replaced both my wish bone arms due to corrosion, after about two months, a knock appeared when breaking slightly. Two garages failed to find the problem, so I decided to invest in taking my car to our local Audi garage in Swindon. They found that the near side lower control arm bush required tightening which removed the problem. However, they advised that they had found only one large washer on the control arm bush, and having looked at the diagram for this bush, two large washers - one on either side of the bush was shown.
Can anyone advise if one or two large washers are fitted to their TDI?
 
H-M3 said:
What’s the update?
Click to expand...
Hi, Thanks for checking up ;)

My update is I'm not 100% sure of what is causing the knock. However, with everything else pretty much checked or ran through, I think it is probable it will be topmount/suspension related. Since the conversation above I've even had the car on a ramp which was equipped with powered/hydraulic play detectors so I could let the ramp do all the pushing and shoving while I looked for the cause of the problem... but I still couldn't locate the source of the knocks.

The car has pretty tired suspension anyway so I'm going to start accumulating all the parts to do a complete refresh front and back including all bolts, top mounts etc.
 
mtl said:
I would advise to change all four shocks. If front are shot, the rear are shot to.
Click to expand...
I’m on a budget so just ordered the fronts for now. Anybody suggest aftermarket rubber sleeves for front shock mounts please? (Dust cover) I believe
 
Decidiver said:
Having replaced both my wish bone arms due to corrosion, after about two months, a knock appeared when breaking slightly. Two garages failed to find the problem, so I decided to invest in taking my car to our local Audi garage in Swindon. They found that the near side lower control arm bush required tightening which removed the problem. However, they advised that they had found only one large washer on the control arm bush, and having looked at the diagram for this bush, two large washers - one on either side of the bush was shown.
Can anyone advise if one or two large washers are fitted to their TDI?
Click to expand...
Update on the above query, one or two large washers either side of the bush? Having took the car for yet another inspection, who printed off the diagram of the suspension and general layout, it was decided that only one large washer should be fitted.
 
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