Rear Shocks Stiff Loud and Thumping After Replacement
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Joined: Apr 2020
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2014 GL450
Rear Shocks Stiff Loud and Thumping After Replacement
2014 GL 450 was skipping around in the rear and intermittently losing some air. Replaced the struts and airbags myself with non-ADS Arnott struts and airbags from Rockauto. The car is holding air nicely and not skipping sideways anymore but very stiff. Loud over bumps. The right rear is extra thumpy. Hard to explain. I’m wondering if I need the air pressure calibrated? I even sent the right rear back and exchanged it. I suppose ball joints could be considered too. I’ve done the front and rear stabilizer links recently. Not much else in there to swap. Very frustrating after that amount of work.
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From: Scottsdale, AZ
'13 CLS550; '21 G550; '16 GL450 Formerly - '03 CLK320, '11 ML350, '09 E350
I'm having the same issue. Just replaced both air bags and the passenger side rear is still making a loud thumping when going over speed bumps or decent size bumps in the road. I did not replace the shocks but did not see any signs of leaking when I replaced the bags. Really don't want to throw money at parts that might not need replacing.
Anyone help on this?
Anyone help on this?
Thread Starter
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Joined: Apr 2020
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2014 GL450
What is the torque value for the lower strut mount nut/bolt that passes through the bushing?
I checked the bushings where the rear struts mount, they look fine. I see I should have torqued the lower strut mounting bolt with the truck on the ground, sitting on the bushing, but I did it in the air.
I'm wondering if that would cause the stiffness I'm experiencing. Makes sense that if the shock is sending all impacts straight into the control arm instead of the rubber bushing, it would feel stiff and loud over bumps. I'll investigate further.....
I checked the bushings where the rear struts mount, they look fine. I see I should have torqued the lower strut mounting bolt with the truck on the ground, sitting on the bushing, but I did it in the air.
I'm wondering if that would cause the stiffness I'm experiencing. Makes sense that if the shock is sending all impacts straight into the control arm instead of the rubber bushing, it would feel stiff and loud over bumps. I'll investigate further.....
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2014 GL450
I loosened the rear nuts and put the car on the ground then tightened them to 180 ft lbs. The right rear still has a sloppy feeling on bumps. The lower bushings looked good when I replaced the struts. I'm thinking ball joints since they are original and I'm at 75k miles. Drove a dirt/gravel road for a holiday light show over the weekend and felt it the whole time. I felt it in the left front too. I hoped to remedy this on my own but now I'm throwing parts at the car. With the rear in the air and the wheels on, I feel no play when manipulating the wheels. The ball joint boots look OK. I guess it's time for a trip to the shop unfortunately.
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2003 E320 4matic wagon
I loosened the rear nuts and put the car on the ground then tightened them to 180 ft lbs. The right rear still has a sloppy feeling on bumps. The lower bushings looked good when I replaced the struts. I'm thinking ball joints since they are original and I'm at 75k miles. Drove a dirt/gravel road for a holiday light show over the weekend and felt it the whole time. I felt it in the left front too. I hoped to remedy this on my own but now I'm throwing parts at the car. With the rear in the air and the wheels on, I feel no play when manipulating the wheels. The ball joint boots look OK. I guess it's time for a trip to the shop unfortunately.
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2014 GL450
Local German indy had the car for a week. He drove it several times and felt it, but took it all apart and found no problem. He recommended going back to OEM MB struts and said he doesn't recommend Arnott. I think I'll have to get used to the sloppiness and stiffness. The OEM parts are not worth the cost and trouble to replace AGAIN.
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Member
Joined: May 2010
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2003 E320 4matic wagon
On your vehicle, does the ride height move up and down with the ride selector - sport/comfort/off road?
On my 2014 gl550 205k miles I’ll be changing mine out (again) due to leakage of new rear struts (new struts lifetime replacement warranty) and will also be replacing air bags and all bushings on rear lower frames. I tow 2 trailers of various weights (1 medium, 1 heavy) and perhaps that contributed to strut premature failure though it shouldn’t have based upon shock loading data. Will take photos when on lift & disassembled and try to diagnose with data measurements. Will keep you posted. Cheers,
On my 2014 gl550 205k miles I’ll be changing mine out (again) due to leakage of new rear struts (new struts lifetime replacement warranty) and will also be replacing air bags and all bushings on rear lower frames. I tow 2 trailers of various weights (1 medium, 1 heavy) and perhaps that contributed to strut premature failure though it shouldn’t have based upon shock loading data. Will take photos when on lift & disassembled and try to diagnose with data measurements. Will keep you posted. Cheers,
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2014 GL450
I don’t have the selectable modes. Also the car does not have ADS for what it’s worth. Unfortunately this started with strut replacement and I may be doing the job again with different brand struts. I have the Arnott compressor and it’s loud no matter how I mount/hang it. I’m unhappy with Arnott.
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2003 E320 4matic wagon
That experience is a negative one evidently.
the compressor should not be that loud. May be worth checking the deflate side on the valve block. Can do this manually with a reasonable scanner, and, check air bag pressurization- correct or over - which could be indicative of a “loud” compressor whereby insufflation is fighting an over-pressurized air bag.
I had an instance on my wife’s 4matic wagon where this occurred and it rode like a stiff beast until I corrected the issue. Not sure why it occurred only after replacing rear struts- did not occur before this. Was this the case with yours as well?
the compressor should not be that loud. May be worth checking the deflate side on the valve block. Can do this manually with a reasonable scanner, and, check air bag pressurization- correct or over - which could be indicative of a “loud” compressor whereby insufflation is fighting an over-pressurized air bag.
I had an instance on my wife’s 4matic wagon where this occurred and it rode like a stiff beast until I corrected the issue. Not sure why it occurred only after replacing rear struts- did not occur before this. Was this the case with yours as well?
Thread Starter
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2014 GL450
The rough ride started after the struts and bags were replaced. I considered the air pressure being too high because it seems like the bags are overinflated. What scanner did you use and what pressures? I'd be willing to get a scanner and do this myself if I can. Love to try it and report back...
Member
Joined: May 2010
Posts: 89
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2003 E320 4matic wagon
The rough ride started after the struts and bags were replaced. I considered the air pressure being too high because it seems like the bags are overinflated. What scanner did you use and what pressures? I'd be willing to get a scanner and do this myself if I can. Love to try it and report back...
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Joined: May 2021
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From: B.C
2012 Mercedes GL350
I'm having the same issue. Just replaced both air bags and the passenger side rear is still making a loud thumping when going over speed bumps or decent size bumps in the road. I did not replace the shocks but did not see any signs of leaking when I replaced the bags. Really don't want to throw money at parts that might not need replacing.
Anyone help on this?
Anyone help on this?
Member
Joined: Jun 2018
Posts: 150
Likes: 23
2017 GLS450, 2013 GL450, RIP 2011 GL450 (totalled)
I had two drivers side Arnott rear bags blow out within months of installation and no towing/hard driving. The front are new struts (non-ADS) from Arnott and their shock absorption is terrible and they clunk/groan depending on what kind of depression or bump I'm going over. The ride on the highway is smooth once it lowers the pressure above 60mph (or whatever the speed is) but the ride around town feels like my tires are at 80 psi. Not sure what to do - they are under warranty but I feel like I'm just going to get the same crappy product back. Should have gone with OEM or Bilstein! Maybe I'll get new ones and sell them, and buy OEM or Bilstein. Just hesitant o spend the money if my engine is ticking time bomb at 145k.
Newbie
Joined: May 2021
Posts: 6
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From: B.C
2012 Mercedes GL350
I had two drivers side Arnott rear bags blow out within months of installation and no towing/hard driving. The front are new struts (non-ADS) from Arnott and their shock absorption is terrible and they clunk/groan depending on what kind of depression or bump I'm going over. The ride on the highway is smooth once it lowers the pressure above 60mph (or whatever the speed is) but the ride around town feels like my tires are at 80 psi. Not sure what to do - they are under warranty but I feel like I'm just going to get the same crappy product back. Should have gone with OEM or Bilstein! Maybe I'll get new ones and sell them, and buy OEM or Bilstein. Just hesitant o spend the money if my engine is ticking time bomb at 145k.
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gl450
I had two drivers side Arnott rear bags blow out within months of installation and no towing/hard driving. The front are new struts (non-ADS) from Arnott and their shock absorption is terrible and they clunk/groan depending on what kind of depression or bump I'm going over. The ride on the highway is smooth once it lowers the pressure above 60mph (or whatever the speed is) but the ride around town feels like my tires are at 80 psi. Not sure what to do - they are under warranty but I feel like I'm just going to get the same crappy product back. Should have gone with OEM or Bilstein! Maybe I'll get new ones and sell them, and buy OEM or Bilstein. Just hesitant o spend the money if my engine is ticking time bomb at 145k.
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2014 GL450
It feels like my rear tires are made of stone, and the right side has sloppiness and feels like there is play. I am going to order OEM struts soon and see if that fixes it, My original problem was air loss and this stiff ride started when I replaced the struts and bags with Arnott stuff. Previous owner replaced the front right with Arnott and went back to OEM after a few weeks. I thought Arnott was a good OEM alternative but seems like a big step down.
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2017 GLS450, 2013 GL450, RIP 2011 GL450 (totalled)
At low speeds, i.e. under 10mph, if I go over a deep depression and the frame pushes downward on the struts there is a kind of rubbery/metal bottoming out noise that I would expect from a rusted out Mercury Topaz. It also does it at higher speeds, say around 30 mph, but just not as audible with the road noise etc. The sound comes from what seems to be the top of the struts and I'm hearing it through the floorboard.
If I go over an incline and when the incline transitions to a decline, the wheels start to go down/struts start to extend and there is a loose clunking sound. It's like 3-4 random clunks that someone hard on hearing may not hear but it drives me crazy for a pair or new struts.
Every bump is jiggled through the car and as I said it rides like the tires are at 80psi.
Oddly yesterday AM I checked my scanner (icarsoft) and it said all the struts were at .27 barG (3.9 psi) at idle while parked. Something doesn't seem right there...still have original compressor which is somewhat noisy. I may check the factory struts on our GLS x166 to see what the pressure values are there (i.e. normal or is there issue with scanner or Arnott)
If I go over an incline and when the incline transitions to a decline, the wheels start to go down/struts start to extend and there is a loose clunking sound. It's like 3-4 random clunks that someone hard on hearing may not hear but it drives me crazy for a pair or new struts.
Every bump is jiggled through the car and as I said it rides like the tires are at 80psi.
Oddly yesterday AM I checked my scanner (icarsoft) and it said all the struts were at .27 barG (3.9 psi) at idle while parked. Something doesn't seem right there...still have original compressor which is somewhat noisy. I may check the factory struts on our GLS x166 to see what the pressure values are there (i.e. normal or is there issue with scanner or Arnott)
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gl450
At low speeds, i.e. under 10mph, if I go over a deep depression and the frame pushes downward on the struts there is a kind of rubbery/metal bottoming out noise that I would expect from a rusted out Mercury Topaz. It also does it at higher speeds, say around 30 mph, but just not as audible with the road noise etc. The sound comes from what seems to be the top of the struts and I'm hearing it through the floorboard.
If I go over an incline and when the incline transitions to a decline, the wheels start to go down/struts start to extend and there is a loose clunking sound. It's like 3-4 random clunks that someone hard on hearing may not hear but it drives me crazy for a pair or new struts.
Every bump is jiggled through the car and as I said it rides like the tires are at 80psi.
Oddly yesterday AM I checked my scanner (icarsoft) and it said all the struts were at .27 barG (3.9 psi) at idle while parked. Something doesn't seem right there...still have original compressor which is somewhat noisy. I may check the factory struts on our GLS x166 to see what the pressure values are there (i.e. normal or is there issue with scanner or Arnott)
If I go over an incline and when the incline transitions to a decline, the wheels start to go down/struts start to extend and there is a loose clunking sound. It's like 3-4 random clunks that someone hard on hearing may not hear but it drives me crazy for a pair or new struts.
Every bump is jiggled through the car and as I said it rides like the tires are at 80psi.
Oddly yesterday AM I checked my scanner (icarsoft) and it said all the struts were at .27 barG (3.9 psi) at idle while parked. Something doesn't seem right there...still have original compressor which is somewhat noisy. I may check the factory struts on our GLS x166 to see what the pressure values are there (i.e. normal or is there issue with scanner or Arnott)
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2014 GL450
FIXED
So I bit the bullet and ordered Mercedes rear struts from FCP Euro. $400 or so shipped. Between last night and tonight I installed them and the ride in the rear is back to original quality. The air bags are still Arnott but the struts are OEM. A valuable lesson learned about saving a few bucks on the aftermarket. The loud compressor from Arnott will be switched out soon, as will the front air shocks that are also Arnott and make a racket. No more Arnott for me! Thanks for everyone's input.
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2014 GL450
That is correct.
I replaced it all with Arnott products, but went back to OE rear struts which appears to have solved the issue of stiff ride, clunking, etc.
The Arnott airbags seem fine.
I replaced it all with Arnott products, but went back to OE rear struts which appears to have solved the issue of stiff ride, clunking, etc.
The Arnott airbags seem fine.
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2017 GLS450, 2013 GL450, RIP 2011 GL450 (totalled)
Got it. I may do the same. Rear shocks are still original and seem fine so far at 145k. But the rear Arnott bags blowing out repeatedly concerns me. Hoping to get back to OEM ride soon!
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2017 GLS450, 2013 GL450, RIP 2011 GL450 (totalled)
Yesterday AM I drove around a parking lot with the suspension on the raised setting. The clunk/groaning got even worse when going back and forth over small depressions and bumps. Has to be the damn struts. Less than two year old Arnott's!
