Clunk when transitioning to engine driving and engine braking (on/off throttle)

[kaanage]

Does anyone know why my car has started to make a slight "clunk" sound when the engine loading reverses?

It wasn't doing it before the weekend :(

[vwthunder]

Guess when you go out on the track and drive the wheels off it, things will happen.

Do you mean when you back off the power? Could be swaybar links, by car does it when i am backing off the power hard, but its a lot lower than yours

[kaanage]

It happens even when the transitions are really gentle like if I feather the accelerator up and down :confused:
Do you think it could be an engine or gearbox mount? It's got less than 16,000km on it :(

[vwthunder]

It happens even when the transitions are really gentle like if I feather the accelerator up and down :confused:
Do you think it could be an engine or gearbox mount? It's got less than 16,000km on it :(

Its only a slight clunk, hmm dont know, could be anything realy, something has moved and knocking, mounts, suspension

Sorry not much help

[Gti Dave]

Hmm...sounds like it could be engine or gearbox mount since you describe it happening that way.

[seangti]

Do you think it could be an engine or gearbox mount? It's got less than 16,000km on it :(
That was my first thought, engine mount. If it's under warranty take it back. I had suspension components changed under warranty and I'd been tracking my car, and they changed the strut top mounts after I'd lowered it. IMO - unless you're being particularly aggressive (no mechanical sympathy) on the track, you're not too likely to break new components so I wouldn't be too worried about that aspect.

But I don't know your driving style :)

[kaanage]

I drive like a granny - aiming for 1100km on this next tank.

OK back to the stealer she goes - an rattle has redeveloped in the door too, that they fixed after a previous cruise (might pull the CAMS sticker off 1st, though).

[vwthunder]

I had suspension components changed under warranty and I'd been tracking my car, and they changed the strut top mounts after I'd lowered it. IMO - unless you're being particularly aggressive (no mechanical sympathy) on the track, you're not too likely to break new components so I wouldn't be too worried about that aspect.

But I don't know your driving style :)


Hahaha you dont know gregs driving style, hmm on the track he is very agressive, I think most people would agree with me, he has to be agressive, because he thinks he is a F1 driver :banana:

Oh he used to race bikes too

[kangfu]

Just quickly undo your swaybar links and go for a drive to see if that fixes it. After a 'spirited drive' one day i came home and car was knocking when reversing out of my driveway. Was just my links loosened from the drive day.

[seangti]

Hahaha you dont know gregs driving style, hmm on the track he is very agressive, I think most people would agree with me, he has to be agressive, because he thinks he is a F1 driver :banana:

Oh he used to race bikes too
haha, so what he lacks in power is made up in aggression and enthusiasm. :)

[kaanage]

Actually, I kinda felt like the Polo had somehow got into the middle of a touring car race in a couple of the sessions on Saturday as I was all mixed up with a pack of Falcadores, some marginally faster than me (which I let past when they got up to my tail) and some marginally slower (which failed to do likewise).:rolleyes:
Somewhere in there was were I picked up the dent, too :(

[kaanage]

Tested a bit this morning by coasting in neutral on flat, uphill and downhill grades and then braking hard and soft - no noise.

I guess it has to be an engine/gearbox mount :frown:

[GoLfMan]

Tested a bit this morning by coasting in neutral on flat, uphill and downhill grades and then braking hard and soft - no noise.

I guess it has to be an engine/gearbox mount :frown:
bit of a bugger. Maybe have a go at checking the tensions on the mounts?

Or what about the DMF? Could that be failing? I've noticed a clunk when I back off too.

[kaanage]

Or what about the DMF? Could that be failing? I've noticed a clunk when I back off too.
But it's only 16,000km old :cry:

[GoLfMan]

But it's only 16,000km old :cry:
There have been stories of them failing long before then......

[kaanage]

So would I be better off taking my car to the dealer that I bought it from or is any VW dealer OK?

[seangti]

So would I be better off taking my car to the dealer that I bought it from or is any VW dealer OK?
Any of em will have to help you. National warranty. I had usually called em first to ask that I come down and they have a quick look, was always met happily by the guys at my local (highway auto - springwood).

[kaanage]

So it seems my passenger CV joint is failing which is causing the clunk - the car was less than 16,000km old when this started happening :confused:
Plus it isn't covered by warranty since the car has modified suspension & has been tracked so I had to pay for the diagnosis :P
Looks like it's gonna be expensive :facepalm:

Should I do another track day as is to finish the CV right off?:cookie:

[Buller_Scott]

damn man! what are we talking - a couple of grand?

that's scary.

[vwthunder]

- unless you're being particularly aggressive (no mechanical sympathy) on the track, you're not too likely to break new components so I wouldn't be too worried about that aspect.

But I don't know your driving style :)

I guess anything can fail, maybe just unlucky

[noone]

I'd get that in writing. If they change it and the issue is not resolved, I'd want some paperwork for an 'engineering' refund.

They're supposed to be the experts, shoudn't have to pay excessively for them to diagnose, I'd also ask for their hourly rate. if its more than a few hours, I'd ask for a report as I cant imagine what they did with the time.

[kaanage]

I have a printed service report that states the issue is the passenger side CV joint plus a comment below that states the vehicle has modified suspension so is ineligible for warranty on suspension, drivetrain and possibly gear box.:emo_baghead:

The pricing for one VW CV joint is just under $300 and they recommend replacing both on the "if one is gone, the other is going" principle. I'm thinking I'll wait until this one get really bad or the other starts going before replacing either.

[BLAKROC]

I've got a similar problem, although I don't think it's CV related. Basically, when I go to shift gear and push down the clutch I get a slight jerk of the steering wheel and a little bit in the accelerator pedal - more so with moderate engine revs/load. Nothing major but it does seem to slowly be getting worse, the car is about a month of its 90k service, so i'll bring it up with the w/shop then..

In the meantime any ideas? I've had both lower control arms done late last year under extended warranty, reckon it could be the engine/gearbox mounts. The car has been on H&R 35mm springs for about 40k, the shocks still seem surprisingly healthy :)

Cheers

[kaanage]

Well it looks like the dealer has misdiagnosed the cause of the noise - and charged me for it since they deem the car to be out of warranty :mad:

A mechanic I know and trust is currently investigating the engine mounts (my suspect) and suspension components :facepalm:

[kaanage]

Update: if anyone cares ;)

My mechanic changed the RH engine mount and this had greatly reduced the noise (which has slowly been getting louder) and, if I am very gently with accelerator transitions it's unnoticable, but generally it's still there so he thinks the torque arm (dogbone mount) bush has also developed slack in it.

It certainly isn't the CV joint as the dealer diagnosed, since reducing engine movement wouldn't affect noise in a CV joint at all :mad:

[Bflat]

Update: if anyone cares ;)

My mechanic changed the RH engine mount and this had greatly reduced the noise (which has slowly been getting louder) and, if I am very gently with accelerator transitions it's unnoticable, but generally it's still there so he thinks the torque arm (dogbone mount) bush has also developed slack in it.

It certainly isn't the CV joint as the dealer diagnosed, since reducing engine movement wouldn't affect noise in a CV joint at all :mad:

I'd be looking at doing the same thing, my gearbox feels as though it's got too much play (in regards to longitudinal movement, especially when warming up). I'm concerned that by going the APR (or any other tuning company) route with an upgraded dogbone mount it could be too harsh and transfer into the cabin

[Stuwey]

I've got the poly lower mount. A superpro one, to be precise.

Sure, it's got a bit of a vibe to it, but are you here to drive a smooth, creamy S-Class Merc, or a lowered, bumpy, turbo'd hot hatch?

[kaanage]

I'll be refurbishing the original bush and getting a separate torque arm with a polyureathane bush for track use.

But then I've got a TDi and I've seen what the polyureathane bush does to idling vibrations :rolleyes: MOST Gti owners don't seem to mind the added transmitted vibration and really only notice it at idle.

[noone]

Seems to be hit and miss. Mine has never been an issue, others have had a lot of vibration from AC passed through...

Mine was done by a dealer before I learnt to play, not that there is much to it to get wrong. Possibly a brand difference?

[kaanage]

I reckon it's more likely to be owner difference than brand difference.

That said, it could be that some people have installed the stiffer "race" spec polyureathane bushes (both APR and SuperPro have 2 variants) and then find them transmitting an unacceptable amount of vibration...

[Stuwey]

Mine is the 'fast road' insert. Can't see why you'd go any stiffer for something you drive all the time.

[kaanage]

OK, finally got another torque arm with a ployureathane bush (APR fast road) and had it installed. Again, the clunking has been reduced but it's still there :(.

While the car was up on the hoist we rechecked the driveline and the only thing noticable is a slight amount of backlash in the differential (nothing at all at the CV joints). My mechanic thought the amount of backlash was pretty normal but also that the Polo (VAG cars) may be tighter in this area than the cars he normally deals with.

So the cure would seem to be a new diff :facepalm:

[GoLfMan]

So the cure would seem to be a new diff :facepalm:
who cares, drive it until it pops, then chuck an LSD in there. :cookie:

[kaanage]

If I can't get it warrantied :facepalm:, then that is EXACTLY what is going to happen :cookie:
My only concern is that if it grenades badly enough, it may take out the rest of the gearbox internals and cases with it so I will be monitoring the noise level VERY carefully.

[Tim]

Have you guys ruled out the dual mass flywheel yet? Ive heard of quite a few being replaced on the diesel golfs.
There are a couple of videos on youtube showing the amount of play that exists in a failed one.

[kaanage]

The car was in neutral when we had it up on the hoist and checked the backlash - I may have to try it again, in gear :confused:

[kaanage]

I had the clunk diagnosed by Burwin VW and they said it was due to the passenger front hub bearing failing because a stretch nut there had been loosened and retightend when my cup kit was fitted and the nuts need to be replaced. I bought a bearing kit from them plus nuts for both sides to get my mechanic to fit them. Funnily enough, the clunk was reduced after the Burwin visit so I wonder if one of their mechanics tightened the hub nut when inspecting it.

My mechanic couldn't see any reason why the hub nut would have been loosened when the cup kit was installed (by someone else) but replaced the bearing on my instruction and now the clunk is gone. The original bearing seems OK (smooth and quiet) so I can use it as a spare when I kill one.

Even though Burwin wouldn't cover the bearing under warranty, I'm happy with them as their diagnosis seems to have been at least reasonably accurate (although I did have other work done to the front that could have removed the cause too) and I was only charged a small inspection fee. Unlike the the a$$holes that misdiagnosed my car who spun me the line about it being a CV joint and charged me heaps for the bs diagnosis :mad:. I'm going to confront them about this and give them a chance to respond before naming the morons.

[csimpson]

Very interesting, thanks for that. Any idea of the price for the bearings? I may replace mine.

Also swtiching to a single mass flywheel with the new clutch, so that may help...

[kaanage]

Here is what happened when I discussed the faulty diagnosis with the original dealer (Barloworld Moorabbin :P).
http://www.vwwatercooled.org.au/forums/f40/misdiagnosis-dealer-what-next-64680-4.html#post781337
Needless to say, I won't be going back there and don't recommend anyone else should, either

[csimpson]

Switching to my new clutch I have no clunking now.

HOWEVER, I think the ECS 14lbs flywheel or thrust bearing is ****ed (in the new kit), it's making a terrible noise at idle and below 2500RPM. I'm taking it back to Camden GTI tomorrow for them to diagnose and fix: if it's either the flywheel or the bearing, I'm going to be kicking up a huge fuss at ECS.

There's always something wrong...

[VWindahouse]

It's unfortunately a standard side effect with the light weight flywheel mate. I have the same one from ECS. I do however remember Jimmy saying a part fix is using a new OEM bearing not the ECS one. He did this with mine and I only hear the chatter noise at idle when I have the aircon pumping. But even then a little rev will usually help dissipate it.

Hope it helps!

[csimpson]

Surely something up with the flywheel - it sounds worse than a diesel! I've posted a video in the What Did You Do Today thread, can you share your experience?

[sambb]

sorry - I'd started a new thread on this same problem as what Kaanage had experienced until I dug this one out of the achive.

I too have this knocking when the engine is ever so slightly loaded/unloaded with the throttle at low rpm.

To test whether the front wheel bearing preload stretch nut has loosened (it may have since both inner driveshaft boots were done on the car the year before I bought it) I plan on tightening it slightly and then seeing if the knocking goes away. If it does i'll order new stretch nuts but I'm unsure how to do the preloading. I'm ok with the castellated nut/cotter pin method but that requires you to take up the tension and then back off from there to a running postion. But I'm unsure if this is the way to go with a stretch nut which by definition shouldn't be backed off from its final position as this voids its ability to hold a certain torque setting doesn't it? Or are they fitted with a torque wrench setting?

So how do I go about finding the correct pre load considering also that the original bearings ( 6yo 28k km) will likely remain in the car?

thanks for any help
sam

[kaanage]

Actually, the hub replacement didn't quite eliminate the noise - it did reduce it to just a 4th and 5th gear issue at low rpm (see http://www.vwwatercooled.com.au/forums/f40/misdiagnosis-dealer-what-next-64680-4.html#post782189 for more details). There may have been a slight amount of stretch on the hub nuts but it could also have been the bolts holding on the control arms (I had the SEAT Cupra rear bushes installed at the same time).

The noise finally went away after I installed some subframe sleeves that Eddy had made up a while ago (I bought the last set).

Sorry for not updating this thread properly back in the day but it died with the tangent discussion about lightweight clutch replacements and I didn't think anyone was still interested in the original issue. I will see if I can get the torque for the hub nuts for you.

edit
BTW sambb, your inbox is full so I couldn't reply to your PM on this so I'd check the bolts for the front control arms and subframe as they seem more likely culprits to me, now.

[sambb]

righto, thanks for getting back to me on the forum. It really is a chorus of noises in front of me now. Even though everything looks to be ok its going to cop a complete re bush after I check the front hub nuts. If that doesn't do it i'll order a new set of subframe stretch bolts.
thanks
sam

[Polo GTEye N9]

Hi Sambb, a PM to Eddy would be wise.

Eddy has done lots of work and sorted thru the front subframe, LCA etc etc on our Polos. Eddy also found that the LCA front bolt was 1.5mm smaller than the sleeve it goes into to. So he brought new bolts with thread all the way along the bolt, result- no more movement slack!

I am sorting my front end out prior to fitting new front & rear suspension and bushes etc. cheers Al

[kaanage]

Eddy also found that the LCA front bolt was 1.5mm smaller than the sleeve it goes into to. So he brought new bolts with thread all the way along the bolt, result- no more movement slack!

Hmmm. I have to disagree with Eddy on this one - there are sound engineering reasons for the VW arrangement with the LCA front bolt. The thinner shaft ensures that the maximum stress is in this area rather than at the thread roots which GREATLY enhances the fatigue life of the bolt. With the full length thread the bolt will fail earlier since the thread roots are stress raisers.

It would be much better to add a polyureathane sleeve (fitted via a spiral slot if it's too stiff for a lengthwise slot)

The subframe sleeves I mentioned before are a great idea, though

[sambb]

So the standard bolts only have thread where its needed but this undersizes the shaft along the pivot. hmm thanks for that. I have access to a whole variety of high tensile bolts at work to at least try out temporarily on the front LCA bushes to eliminate that. High tensiles will be strong enough/safe won't they? VW don't have any super metallurgy going on with simple bush cross bolts do they, other than the potential issue that kaanage raised?

[kaanage]

For a short period, a fully threaded bolt of the same quality as the OE one would be OK - fatigue failure is a long term issue for most parts (a lot of cars would never have this bolt removed in their lifetime), unless the part was critically optimised in the first place and I'd lay long odd that this one isn't.

Why not just wrap the shank of the OE bolt with some sheet metal?

[Eddy]

Hoyhoy.

Sorry folks I only just spotted this thread, Greg the threaded shank bolts were the replacement part from VW, plus I did add some sleeving on
the little bit of blank shank left, on top of that there is added material as to where it goes in (thickness & minumun diameter)(zero freeplay).
Info a lot of VW bolts are of 12.2 tensile grade, normal hi-tensile = 8.8.

[sambb]

so eddy, did you just ask for replacement LCA front bush bolts and they just gave you different ones to the original fitment, or did you have to specify that you wanted ones with a different shank? I've just ordered replacements from VW so wondering if I need to cancel the order in favour of slightly different bolts.

thanks
sam

[Eddy]

Hoyhoy.

I just went for replacements, so I would say that you will get the same as me, which took two weeks.

[Eddy]

Hoyhoy.

Folks have a read for two post of this shortcut...To Improve Me Polo. - Page 7 (http://www.ozvolks.com/forums/showthread.php/1377-To-Improve-Me-Polo?p=7691&viewfull=1#post7691)

I had only a little bit of slop in the torque link, now she's much better & much smoother with take-off.
Ya have to think of all the forces acting against this one & only mount fighting to keep the whole engine in place, any free play will be felt.
It did remind me of the old Cooper S days, they were a sad case in this area.

[sambb]

Well I just picked up my VW LCA front bush bolts and they are the full length thread type that Eddy got. All I can say is that even with the full threaded version where the shank is larger outside diameter than the original fitment ones, the amount of free play within my superpro bush sleeves is ridiculous! Can definitely see how this could cause front end noises.

But from a performance point of view I couldn't agree with you more Eddy. You can wiggle the bush nearly through a degree on the bolt - each side that'd be nearly 2 degrees total which would be a hell of a lot of toe mm change under braking like eddy said. If you didn't have really stiff rear LCA bushes I reckon the wishbone would be squirming around all over the place. I haven't done this with the original VW bush though - maybe the superpro sleeve is larger I.D than the VW one - can't say yet.

I'm going to see about getting a new inner sleeve spun up for the bushes, to tighten up the tolerances to the VW full thread bolt. When I finally put it all back together the LCA will be fully superpro'd so if the clunking continues then it ain't the bushes!!

sam

[Eddy]

Hoyhoy.

CLUNKING NOISES, folks I have to say even with everything nice & tight I still have noises, may be I have things too tight, but with front spring ratings of 350lb & now going to 425lb, you do expect some noises, old age helps with this.
But the steering is a lot better, even with -3% camber she's steer's a lot better than ever.(toe alignment is a big thing also)
Also have to reconfirm my statement from post No-53 in this thread, zero free play in the torque link = much better.

[sambb]

Well I've done my LCA's with superpro rear and front bushes ( fronts have new VW bolts with full length thread and new tighter inner bush sleeves machined up to fit them with zero freeplay). Couldn't be happier with the result for the handling. I still have stock springs and couldn't notice any adverse change to harshness at all, yet it turns in and points so accurately now and has even more of that euro planted feel - super happy. Its a generally quieter front end now with less creaks etc
HOWEVER.. the clunking is still there and I'm now convinced that its inner driveshaft freeplay. When I had it apart for the LCA job, physically the freeplay didn't feel like that much but when you twist the driveshaft back and forth it generates a really audible clunking and I'm pretty sure is the same sound I'm getting when I drive. I just can't believe how loud it is - it 'sounds' like a real problem although I'm sure it will be fine.

My car had its driveshaft inner boots replaced before I bought it. Is there anything simple they might have buggered up that could be contributing to the sound, is this something thats inherent with these gearboxes/shafts or is mine an odd one out?

[pologti18t]

I had a similar noise... that got worse in warm weather.
After reading all these posts I lubed the rollbar bushes and droplinks.... and I also lubed (silicon spray) the hinges and strikers of bother front doors.

Result... noise gone. Was it the bushes OR the door hinges