940: Clunk - Passenger Front

[Fresh Air Inspector]

Hello All,

Hopefully one of you can shed some light on a clunk I have. It only happens when the right front wheel drops into a pot hole or off the edge of a raised piece of pavement.

Background;
About 14K km ago (April 2019), I replaced the ball joints (NAPA), all the front suspension bushings (Meyle except control rod end - Urethane), sway bar links (Meyle on control arm end and Urethane on sway bar end), shocks (Monroe), strut mounts (KYB), strut bearings (KYB) and top spring plate (Volvo). I also swapped out the Koyo (original rack ~275K km), for the TRW unit from a lower mileage 760. The passenger inner tie rod had some play so I replaced it. At the same time I had the front end aligned. The alignment guy mentioned that he found some play in the rack.

Current Situation;
Some time after the above repairs I noticed a slight clunk in the right front over certain bumps (ones that cause the front wheel to drop suddenly). This became progressively worse so my assumption was play in the rack. I sent the rack out to be rebuilt and after installing it a week ago I was very disappointed to discover no improvement.

I have it booked in for an alignment in 2 weeks time so hopefully one of you has an idea as to what it can be. I concerned it may be related to the rebuilding of the front struts although in theory the 'clunking' should have started immediately.

Looking forward to your feedback.

[Mr. V]

I just got rid of a bad clunk by changing strut mounts, but it sounds like you did this recently.

People say that it's a good idea to verify that the bolts holding the front cross member to the body are tight, as loose bolts will cause a clunk.

[Acke]

Could there be play in the driver side inner tie rod or a premature failure of the already replaced one, or were they both replaced when the rack was rebuilt? When the inner tie rod on the driver side on my beater 9 broke it clunked on sudden drops and was a PITA to try to diagnose on the garage floor. Luckily it was found in the yearly inspection. The other thing that comes to mind when looking at your list would be a slightly loosened gland nut.

[2manyturbos]

Almost every time I have had a 240 with a "clunk" as you describe it has been the bushing at the rear of the control arm that attaches to the frame.

[Fresh Air Inspector]

Hello All,

Great feedback. I will check the 'front cross member bolts' and 'lower control arm bolts (all of them). I will double check the 'inner tie rod' but both were replaced when the rack was rebuilt.

I probably won't have an thread update until after the 23rd when it goes in for an alignment.

Fingers crossed a solution is found to this annoying problem. :-)

[sharkbait66]

Do you have shorter springs on the car, like IPD springs?

[Fresh Air Inspector]

Hello sharkbait66,

Car has stock springs front and rear. These have not been cut or modified so ride height is stock albeit probably slightly lower due to age / mileage (~285K km). Rear sway bar is from a turbo sedan.

[Fresh Air Inspector]

Hello All,

Yesterday (23/11), the 940 went in for a front end alignment. Technician could not find anything loose in the front end but did hear the clunk when he rolled the car off the alignment rack. We threw some ideas around and both of us settled on the strut shock absorber cartridge. Pity as I replaced these, the bearing plate and top spring plate, 16K km (10K mi), ago in April 2019.

I'm hoping to replicate the 'clunk' in my garage but it will be a long shot as trying to 'drop' one side of the suspension won't be easy. Fingers crossed. :-)

I'm going to replace the shocks but it will need to wait a few weeks - other projects competing for my time. I will update this thread when I have completed this.

[tintintin]

Hopefully someone with better experience in this will post soon, but IIRC there is a previously discussed issue with some aftermarket strut inserts requiring spacer washers, or the washers becoming dislodged, or needing the gland nuts retightened.

Also, some aftermarket bearing rings and top mount plates have documented quality problems. Which brands did you use?

[Mr. V]

Make certain that the nut on top of the strut is tight.

[Fresh Air Inspector]

Hello tintintin, Mr. V,

Appreciate the feedback.

Shocks (Monroe gas), strut mounts (KYB), strut bearings (KYB) and top spring plate (Volvo). Both top nuts were checked a few weeks ago - both were at the correct torque value.

tintintin - interesting comment regarding washers / spacers / gland nuts. It aligns (pardon the pun), with my gut feeling about the shock / strut being the issue.

Hopefully within the next month I'll find some time to pull the strut and find the issue. Fingers crossed.

For those of you in the US, enjoy your Thanksgiving.

[2manyturbos]

Originally Posted by Fresh Air Inspector

Hello tintintin, Mr. V,

Appreciate the feedback.

Shocks (Monroe gas), strut mounts (KYB), strut bearings (KYB) and top spring plate (Volvo). Both top nuts were checked a few weeks ago - both were at the correct torque value.

tintintin - interesting comment regarding washers / spacers / gland nuts. It aligns (pardon the pun), with my gut feeling about the shock / strut being the issue.

Hopefully within the next month I'll find some time to pull the strut and find the issue. Fingers crossed.

For those of you in the US, enjoy your Thanksgiving.

He is assuming you have a 240. I did as well until I re-read the 760 rack comment. Early 240 struts have a removable spacer at the bottom of the strut housing. They can easily fall out when the cartridge is being replaced.

[dl242gt]

How are the diagonal strut bar bushings? The ones that clamp around the control arm and have a large bushing at the rear to the body. The control arm bushing can make a clunk as well. But the diagonal brace bushings where it meets the control arm are a common wear location.

[Fresh Air Inspector]

Hello All,

Just to clarify the vehicle is a 1994 940 T. I temporarily installed a rack from a 760 because the original rack (Koyo), had play in it. The car was 'clunking' before the racks were swapped and unfortunately continued after the swap. Since the 760 rack had some serious mileage on it as did the original Koyo (~285K km), I figured having the Koyo rebuilt should / would solve the problem - wrong!!

So, just to recap, the rack, inner / out tie rods, every bushing in the front end (except the sway bar to frame mounts - good shape), balls joints, shocks and all the top mount hardware have been replaced. Plus an alignment after the rack install. The clunking continued (right side only).

As mentioned, the alignment guy and myself are of the opinion that the problem is in the strut and or shock. Probably the latter. Unfortunately it will be weeks before I will time to pull the strut and disassemble it. I plan to replace the shocks again while I have it apart - probably go with KYB instead of the current Monroe. I've found them to work well in other vehicles.

I'll update this thread when it get the strut on the bench - fingers crossed. :-)

[Chico]

Following along--very similar issue over here with similar new parts (minus rack) and a 940t wagon

[Fresh Air Inspector]

Hello All,

After MUCH delay I was finally able to replace the front strut shocks in my 940. The first test drive was today (Tue 19/01), and the front end clunk is gone!!!!! :-)

Other projects had priority including replacement of a leaking heater core in my 940 (what a PITA), and then along came a moron that decided not to return the strut spring tool to the only rental outfit in my area. Yes, he lost his deposit but they only charge you the value of the tool – not much of a deterrent.

To recap. About 2.5 years / ~20K km (12K mi) ago I replaced front suspension bushings (Meyle except Urethane for Control Arm Stays), strut shock (Monroe gas), strut mounts (KYB), strut bearings (KYB), top spring plate (Volvo) and ball joints (NAPA). Not long after I replaced the anti-roll bar links, upper ones in Urethane. At that time I also replaced original Koyo steering rack with a TRW unit from 1987 760 (~180K km). Steering pump from same vehicle. Replaced inner tie rod (passenger side). Despite the low mileage the TRW rack had some play.

About 5 or 6 months ago I started to hear a clunk in the right front when the wheel dropped in pot hole or similar sharp drop off. It got progressively worse so I sent the original Koyo steering rack out for a rebuild. Upon it's return I installed the rack and took the car out for a test drive – much to my disappointment and frustration, the clunk was still there. So onto my trusted front end alignment shop. They aligned the car and could not find any reason for the clunk. However, the tech did hear it when he backed the car off the alignment rack. We discussed possibilities and came to the conclusion that the strut shock must be the cause.

So, I pulled the struts and using my newly purchased strut spring tool replaced both Monroe strut shocks with Bilsteins. Must say it was a challenge to loosen the large top nut that holds the passenger side shock inside the strut. Despite anti-seize compound it was well corroded, the joys of living next to the ocean as well as salt being used in the winter months (the 940 is my DD). Despite copious amounts of WD-40 and heat, the hex head plate decided to break away from the threaded portion so I had to use a hammer and punch to remove the threaded portion. Luckily it came out without damage to the strut itself. The drivers side came out much more easily. Did discover a big difference in quality between Monroe and Bilstein. Monroe used a shorter, by at least 13mm (1/2”), top nut with only 3 spot welds to hold the hex plate onto the threaded portion whereas Bilstein chose a much longer threaded fitting along with 6 spot welds.

I could not find any reason for the clunk – neither shock showed any signs of leakage and both behaved the same when 'bench testing'. All I can surmise is that the passenger side shock had some form of defect.

If anything changes, I will update this thread.

Hopefully the above will be of help to someone.

[Janspeed]

Did you check if the shock cartridges are in fact equal length (the parts inside the strut tube)
If not and it turns out that the Monroe's are in fact shorter then that could have been the cause of the clunking (cartridge hammering up and down inside the struttube). Possibly could have been fixed with some shims under the cartridge.

[Fresh Air Inspector]

Hello Janspeed,

As soon as I had the springs removed from the strut I checked for play between the shock cartridge and the gland nut (forgot the name in my post yesterday Didn't feel any. When the shock cartridge was removed I immediately checked the bottom of the cartridge as well as the top for any 'polished' spots to indicate if any movement had taken place - none. BTW my struts did not have any form of spacer in the bottom. If they did I would not have been able to tighten the Monroe (short), gland nut at the time.

I neglected to compare the overall length of the Bilstein (new) with the Monroe shock cartridge. In hindsight I should have. Today I did a comparison on the 'rebound' speed of the Monroe shocks by pushing the rod to the bottom of the shock and then watching how quickly the gas pressure pushed the rod back up. The passenger side was noticeably slower and usually stopped about 2 - 3 cm (3/4 - 1 1/2"). Both shocks had been stored vertically overnight to ensure the oil was in its normal operating state.

[tintintin]

Originally Posted by Fresh Air Inspector

Today I did a comparison on the 'rebound' speed of the Monroe shocks by pushing the rod to the bottom of the shock and then watching how quickly the gas pressure pushed the rod back up. The passenger side was noticeably slower and usually stopped about 2 - 3 cm (3/4 - 1 1/2"). Both shocks had been stored vertically overnight to ensure the oil was in its normal operating state.

Not always a valid test. First few compressions/rebounds may react quite differently to how the shock acts after it is "warmed up" from several cycles.