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Knocking noise in the rear - SOLVED!!


fergo84

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Hi all,

Just wanna share and not sure if any of you here experience this in your GLC. Had my GLC for 9 months already. Approx 3mths into driving it, i start getting knocking sound coming from the rear. Couldnt ascertain what caused it. Brought it down to the dealer to have them check but couldnt find anything. (i though it was something loose within the suspension system)

It happens when going over uneven roads (which cause your car to flex). most often and obvious when you approach a slope (up or down) at an angle. Funny thing was, it only happens while driving low speed + flexing. Cruising around over uneven roads was ok. 

Got so irritated with the noise, i started my own little investigation. 

1. Removed everything i had in the trunk - Just to make sure it wasnt something i put in the trunk that is hitting something.

2. Rear seat belt buckle knocking against the plastic panels - secured the buckles before driving. the sound was still there.

3. Rear trunk had loose panels - Hard to replicate but i tried shaking some of the panels to see if it makes the same sound. nothing.

4. Rear trunk roller cover (or whatever you call it) - removed the whole roller cover thing and drive around. Sound was still there. 

5. Rear folding seats - folded all seats down and drove to the exact same location that caused the sound every time i drove past. sound was GONE!! Repeated it a few times just to confirm. I was more or less convinced that it was the rear seat latch hitting each other when the car flexes. 

Solution: i used electrical tape to wrap the latch. This caused the rear seat to be latch much tighter in place. Had a test drive for a few days. The irritating sound never came back!!

There are definitely some rattling/knocking noise within the cabin which are inevitable. But this was just too loud and way beyond my acceptable threshold. For those that have the same irritating noise/sound, you may want to give it a try.

 

Cheers!

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Hi fergo84

I also had this same faint knocking sound and I thought it was due to the thermal expansion of the exhaust. 

Would you be able to share a picture of the latch so that I could also have it wrap up?

Thank you.

 

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22 hours ago, GLTAN said:

Hi fergo84

I also had this same faint knocking sound and I thought it was due to the thermal expansion of the exhaust. 

Would you be able to share a picture of the latch so that I could also have it wrap up?

Thank you.

 

Here you go... Simple job. But not sure how long it will last. 

The length of the tape I used abt 4-5inches. I think any longer, the wrap will be too thick n u will probably have trouble latching the seat back. 

20170817_181057.jpg

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On 17/08/2017 at 6:15 PM, fergo84 said:

Here you go... Simple job. But not sure how long it will last. 

The length of the tape I used abt 4-5inches. I think any longer, the wrap will be too thick n u will probably have trouble latching the seat back. 

20170817_181057.jpg

Thanks Bro.

Will give it a try too. 

BTW, do you experience crabbing of your wheels especially on wet surface (eg. in car park)? CNC told me its because our tyre profile is too THICK and changing rim to at least 19" should solve this problem...I am pissed....

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On 17/08/2017 at 6:15 PM, fergo84 said:

Here you go... Simple job. But not sure how long it will last. 

The length of the tape I used abt 4-5inches. I think any longer, the wrap will be too thick n u will probably have trouble latching the seat back. 

20170817_181057.jpg

Which part of the rear bench is this? I don't remember seeing this latch when i fold down my rear seat backs.

My latch is those that have 2 configuration: 1) when down, the seat backing will be in normal recline angle 2) when up, the seat backing will be more upright, freeing up abit more cargo space. 

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13 hours ago, GLTAN said:

Thanks Bro.

Will give it a try too. 

BTW, do you experience crabbing of your wheels especially on wet surface (eg. in car park)? CNC told me its because our tyre profile is too THICK and changing rim to at least 19" should solve this problem...I am pissed....

Its not the tyre profile.... even 20inch also get it in car park.

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10 hours ago, Michaeltoh said:

Its not the tyre profile.... even 20inch also get it in car park.

I was considering to upsize my rim to solve this crabbing issue...heng you alerted me on this...thanks...

Any solution to this crabbing issue?

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On 18/08/2017 at 6:59 PM, GLTAN said:

Thanks Bro.

Will give it a try too. 

BTW, do you experience crabbing of your wheels especially on wet surface (eg. in car park)? CNC told me its because our tyre profile is too THICK and changing rim to at least 19" should solve this problem...I am pissed....

yes i do experience that as well. but from what i read online, its a known problem for GLC. i do go very slow though just to minimise the crabbing. it just feels like the suspension is gonna break. hahaha... 

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On 18/08/2017 at 8:54 PM, VRAtenza said:

Which part of the rear bench is this? I don't remember seeing this latch when i fold down my rear seat backs.

My latch is those that have 2 configuration: 1) when down, the seat backing will be in normal recline angle 2) when up, the seat backing will be more upright, freeing up abit more cargo space. 

here you go. a picture from google shows a coupe but the latch is in the same position.

kenzie-wheels-m-benz-glc-300-coupe-rear-seats-all-down-suppjpg.jpg.size.custom.crop.1086x724.jpg

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  • 1 month later...

fergo84 you sir, are an absolute LEGEND!!!!! I had this problem today with my GLC43. Thought it was the air suspension or struts. I did EXACTLY as you (and laughed pretty hard when I read your post just now). Cleaned out the boot etc. Still could not locate the issue.Only heard at low speeds up and down hills and my driveway.

After reading your post I folded the seats down and nothing. I'm taking it back to merc as I don't think some tape is a good enough solution on a $115k car!!

Thankyou so much for your post - this could have gone on for weeks!! Very appreciative.:jig:

 

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  • 1 month later...
On 06/10/2017 at 6:08 PM, SammyW said:

fergo84 you sir, are an absolute LEGEND!!!!! I had this problem today with my GLC43. Thought it was the air suspension or struts. I did EXACTLY as you (and laughed pretty hard when I read your post just now). Cleaned out the boot etc. Still could not locate the issue.Only heard at low speeds up and down hills and my driveway.

After reading your post I folded the seats down and nothing. I'm taking it back to merc as I don't think some tape is a good enough solution on a $115k car!!

Thankyou so much for your post - this could have gone on for weeks!! Very appreciative.:jig:

 

im glad you solved the issue! i doubt merc can do anything about it. a simple solution is good enough for me. i dun want them to start opening up panels (to replace some stuff) and end up loosening something else and can potentially cause those irritating noises somewhere not as accessible as this. 

 

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  • 6 months later...

I tried the electrical tape on the latch, didn't work for me.  I was pretty depressed, until I noticed the luggage compartment cover was open.  Once I closed it, no more rattle.  I can't believe it was that simple, at least for me.   Good luck to all

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  • 1 year later...
  • 1 year later...
On 8/19/2017 at 1:09 AM, Michaeltoh said:

Its not the tyre profile.... even 20inch also get it in car park.

Yes it is the tyres. I have 19”rims on my glc 43. When the original summer  tyres needed replacing I changed to Michelin all weather and crabbing issue has gone. Hope that helps 

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  • 2 months later...

Thank you!!!!! I was ready to trade off my GLC43 because it sounded like it was going to break in half at slow speeds. I thought it was the sunroof and so did my husband. I decided to try your suggestion and I immediately knew you were right! Unused duct tape on those 2 rear seat brackets and it solved it! You just saved me $70k for a new car!! I can’t thank you enough for your post and for the photos as I copied what you did. 

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  • 1 month later...

i just took over a pre-owned GLC250 and with pre-owned, dealer said this was existing problem. test drive wasnt that obvious but after driving it a few more days and the noise seems to get worse or at least getting on my nerves. this thread is a life-saver! tried with a seat folded down and already the nosie reduced quite significantly. will defo go full works with the recommendation here!

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