Distinct hard to diagnose “thunk” issue in front end

JordanLee

Well-known member
Joined
Sep 7, 2018
Location
Vancouver/Seattle
TDI
2014 GSW
So I've been chasing this distinct thunk noise (sounds dampened and not metal on metal) from what appears to be the front right upper area of the chassis. It only happens during a sudden drop or sudden bump in the road. A slow drive over a speedbump will not trigger it but a quick isolated drive over the same bump will clearly make the noise. After a bunch of digging on here and other forums, I narrowed it down to endlinks, subframe bolts, upper strut mount. It doesnt sound like subframe bolt shift as it doesnt happen when its at low speed turning so I kinda put that on the backburner.
It is worth to note that I bought the vehicle with a minor front end accident on the same corner to which to which the CV, entire lower control arm assembly, strut assembly were all replaced with used parts from a wrecker. After a week of driving the vehicle I noticed the sound and began trying to diagnose the noise.
I started with the upper strut mount and replaced it and a new bearing with a Lemforder replacement. *I did not take note of the orientation of the arrows and tab* The noise was the same I then replaced the right endlink and entire lower control arm assembly with a new balljoint and bushings. While I was in there I also did the subframe bolts with the Passat bolts and shims.
None of this fixed the issue. I went for a drive with a friend and ran over speedbumps specifically on the right side and he was quick to note it sounded like it was on the upper strut area. I came to the conclusion that the first time I did the strut mount (only having the car a week in) I might not have noted the orientation of the arrows and tab and could this maybe cause the topmount to bind or not allow flex in that specific geometric stress application? I mean if the previous bodyshop who did the repairs also did mistake, and I made it was as well this semi reduces my likelihood that this is the culprit but I mean he had a 1/3 chance and I had a 1/3 chance as well.
I could not find any definitive answer on what happens if you install the strut tophat in the wrong direction, I understand this is a pivotal suspension component for camber and I assume the tophat is slightly on an angle in a certain plain to give the correct geometry, could this be the cause of the clunk/thunk? I read online that its meant to flex in a certain angle only and having it in the wrong direction can cause the geometry to bind and clunk?
I just wanted to see if anyone has any other feedback or things to look for as it appears I've replaced all of the trouble MK5/MK6 chassis parts that cause these front end noises and its driving me crazy.
Thanks!
 

PB_NB

Veteran Member
Joined
Nov 20, 2007
Location
Vancouver, B.C.
TDI
1999 New Beetle
How does it drive? and track? Are you getting pulling or uneven tire wear? My first thought would be sway bar bushings or toasted lower control arm bushings.

I don't think it would be that easy and I sure you have looked at those.

Have you checked the torque mount or dogbone mount in the MK4's. Recently one of my coworkers was complaining that his front struts were done due to a noise.

We popped the hood and moved the engine back and forth and there was the clunk. We looked underneath and noticed that the main bolt holding the mount to the transaxle was sheared off. $4.00 later and it was fixed.

Check this out to see what it looks like.

https://www.hpamotorsports.com/hpa-products/motor-mounts
 

ihatespeed

Veteran Member
Joined
Jan 12, 2013
Location
holbrook, ma
TDI
11 tdi wagon 6mt 15 golf 6mt (Wife's) 2000 Ford 350 7.3l 6mt 4x4 (technically a TDI)
could just be your struts topping out, every MacPhearson strut car Ive ever driven makes a pretty wicked thunk when the road falls out from under the front wheels.
 

JordanLee

Well-known member
Joined
Sep 7, 2018
Location
Vancouver/Seattle
TDI
2014 GSW
Thanks everyone for the reply.

The car tracks straight and has no pull, torque mount appears fine but I should reef on it with a pry bar to be sure.

I bought a set of front Bilstein TCs to see if this recitifies the issue. Along with H&R sport springs. Maybe them being at a different height will cause them not to top out which is bizarre since it’s clearly only the right side.

Endlinks are for sure not the issue as I’ve replaced the entire right endlink and also removed both to see if the issue persisted which it did. I pride on the subframe sway bushings and those appeared okay too.

At this point I’m feeling like it’s gotta be the strut. Either the valving inside is shot or something. I confirmed the other day that the top hat is in the correct orientation as well so that’s not it. So the story continues....
 

IndigoBlueWagon

TDIClub Enthusiast, Principal IDParts, Vendor , w/
Joined
Aug 16, 2004
Location
South of Boston
TDI
'97 Passat, '99.5 Golf, '02 Jetta Wagon, '15 GSW
Could be subframe "knock" which is common on MKV and VI cars. There are fix kits available that anchor the subframe better.
 

JordanLee

Well-known member
Joined
Sep 7, 2018
Location
Vancouver/Seattle
TDI
2014 GSW
Okay wow, thought I'd give a follow up. After going to the next failure point, it was time to do the struts. My friend was nice enough to let me use his hoist and I didnt want to do the entire job again and do springs at another date. So I bit the bullet and bought a used set of H&R Sport springs and Bilstein TC front oem spec/length struts.

I can safely say that the insurance-replaced USED A3 strut they used 8 months ago was COMPLETELY shot. Im talking like press down with 1 finger all the way down and not come back up bad. It was leaking fluid behind the boot and smelled bad.

Despite that I couldnt believe I couldnt feel a difference though, it didnt feel bouncy or undampened, just noisy.

Car now looks amazing lowered and was dead quiet on the way home. Im just super suprised that it was the physical shock to blow and make noise rather than the usual subframe/swaybar endlink clunk that plagues our cars.

Ill upload a video and some photos when I have some time.
 

PRY4SNO

Veteran Member
Joined
May 15, 2016
Location
Edmonton, AB
TDI
2013 Touareg Execline
That's awesome.

I'm really looking forward to installing new suspension in my GSW. Hope it clears up some of the same issues.
 
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