XC70: Suspension - Knock from rear left side

Tatsfield · Jul 24th, 2017, 17:20

My '12 CX70 has developed a knock from the rear left side when accelerating from a stand still or at low speeds. I inspected everything in the boot and wrapped all loose objects in towels to stop any movement. This made no difference. So I booked the car into the dealers for advice. Of course cars know when they are going to the garage and by the time I arrived the symptoms had stopped! The mechanics said that they could find nothing after putting the car on a lift and inspecting the suspension and exhaust. However, a week later and it's started again. This time I intend to remove absolutely everything from the boot and wheel well and see if that solves it. If not, has anyone any advice as to what the fault might be. It only occurs under acceleration and not under braking.

CTCNetwork · Jul 25th, 2017, 14:05

Hi,

Braking lifts the car at the rear. Acceleration lowers the car at the rear.

My initial thoughts would be either the shock is worn or one or more worn bushes.

Have you bump tested both sides at the rear?

Des. . .

tt82 · Jul 25th, 2017, 16:54

Given that it only happens from standstill or at low speed, could it be a seized brake caliper?

Semnoz · Jul 26th, 2017, 13:50

Following on from TT82's suggestion, you could try slowing down to a standstill without touching the brakes, and seeing if it's still knocking when you accelerate. Then do the same after braking, etc...
This might help show if it's related to sticking pistons, or a lip on the rotor.

pierremcalpine · Jul 27th, 2017, 18:37

Quote:

Originally Posted by Semnoz

Following on from TT82's suggestion, you could try slowing down to a standstill without touching the brakes, and seeing if it's still knocking when you accelerate. Then do the same after braking, etc...
This might help show if it's related to sticking pistons, or a lip on the rotor.

Hey Semnoz, I've been troubleshooting a knock in my front end and was wondering if a worn disc with a notable lip could cause a knock...have you experienced this first hand? the disc is at minimum thickness and I do have plans to replace it soon but just curious if this is something that you have experienced.

Semnoz · Jul 30th, 2017, 22:46

Quote:

Originally Posted by pierremcalpine

Hey Semnoz, I've been troubleshooting a knock in my front end and was wondering if a worn disc with a notable lip could cause a knock...have you experienced this first hand? the disc is at minimum thickness and I do have plans to replace it soon but just curious if this is something that you have experienced.

No, I've not had this myself. I was just trying to think of reasons why a brake shoe might be binding with the rotor, which could cause a 'clunk' when you start moving. To be honest, I think it's quite unlikely, unless the rotor had become warped suddenly.

Tatsfield · Jul 31st, 2017, 11:40

OK it's red face time!

I emptied out absolutely everything from under the rear compartment floor, including the newly acquired space saver spare wheel and tool pack. Drove the car and the noise had gone. When I replaced the spare I noticed that it wobbled a bit in the wheel well so I put a wad of bubble wrap under the overhanging rear edge and really tightened down the screw clapping bolt. Still no noise when driven. Have added back the electric tyre inflation pump and the detachable tow hitch, well packed in a padded bag and still no noise when driven. I am now pretty sure the problem was the spare wheel which wasn't supplied with the car. I bought it as I didn't want to be dependent upon the pump and a can of gunk which destroys the tyre in which it is used! But Volvo really didn't make the wheel well friendly to spare wheels.

Keeping everything crossed, I think that I have solved the problem. If it returns to the car, I'll return to this thread. Hopefully some of the advice already given might be useful to other owners with rear clunk problems not involving stowed spare wheels!

tt82 · Jul 31st, 2017, 14:26

At least it appears to be a cheap fix!

Semnoz · Jul 31st, 2017, 16:55

I suspect my spare wheel is just as wobbly...I reckon you must be accelerating harder than I do

Tatsfield · Aug 1st, 2017, 10:16

I come to the XC70 from 15 years of 2+2 Coupe ownership and the muscle memory in the right foot seems to be firmly established!

Jul 24th, 2017, 17:20	#1
Tatsfield Premier Member Last Online: Today 17:47 Join Date: Nov 2015 Location: Poole	Knock from rear left side My '12 CX70 has developed a knock from the rear left side when accelerating from a stand still or at low speeds. I inspected everything in the boot and wrapped all loose objects in towels to stop any movement. This made no difference. So I booked the car into the dealers for advice. Of course cars know when they are going to the garage and by the time I arrived the symptoms had stopped! The mechanics said that they could find nothing after putting the car on a lift and inspecting the suspension and exhaust. However, a week later and it's started again. This time I intend to remove absolutely everything from the boot and wheel well and see if that solves it. If not, has anyone any advice as to what the fault might be. It only occurs under acceleration and not under braking. __________________ 2012 XC70 SE Lux Polestar 230 bhp D5 Auto Oyster Grey

Jul 25th, 2017, 14:05	#2
CTCNetwork Forum Support Team Join Date: Dec 2004 Location: Liège, Belgium View Photos By: CTCNetwork	Hi, Braking lifts the car at the rear. Acceleration lowers the car at the rear. My initial thoughts would be either the shock is worn or one or more worn bushes. Have you bump tested both sides at the rear? Des. . . __________________ Density:- Not just a measurement ~ It's a whole way of Life.! ! ! I drive a Volvo, Please Don't Get In My Way! OldVolvos4Ever He shows up. People die. He vanishes. People should not be afraid of their governments. "He'll deliver more justice in a weekend than 10 years of your Governments should be afraid of their people... "V" courts & tribunals. Just stay out of his way." "I plan to."

Jul 25th, 2017, 16:54	#3
tt82 Forum Support Team Last Online: Nov 28th, 2022 17:33 Join Date: Jan 2009 Location: Here.... obviously!	Given that it only happens from standstill or at low speed, could it be a seized brake caliper? __________________ The more people I meet, the more I like my dog! 2009 V70 D5 R-Design - Jeade'en

Jul 26th, 2017, 13:50	#4
Semnoz Senior Member Last Online: Nov 12th, 2023 19:03 Join Date: Jan 2011 Location: NW	Following on from TT82's suggestion, you could try slowing down to a standstill without touching the brakes, and seeing if it's still knocking when you accelerate. Then do the same after braking, etc... This might help show if it's related to sticking pistons, or a lip on the rotor. __________________ V70 D5 185 SE Lux P3 (with rear integrated booster seats, which the kids love !!)

Jul 31st, 2017, 11:40	#7
Tatsfield Premier Member Last Online: Today 17:47 Join Date: Nov 2015 Location: Poole	OK it's red face time! I emptied out absolutely everything from under the rear compartment floor, including the newly acquired space saver spare wheel and tool pack. Drove the car and the noise had gone. When I replaced the spare I noticed that it wobbled a bit in the wheel well so I put a wad of bubble wrap under the overhanging rear edge and really tightened down the screw clapping bolt. Still no noise when driven. Have added back the electric tyre inflation pump and the detachable tow hitch, well packed in a padded bag and still no noise when driven. I am now pretty sure the problem was the spare wheel which wasn't supplied with the car. I bought it as I didn't want to be dependent upon the pump and a can of gunk which destroys the tyre in which it is used! But Volvo really didn't make the wheel well friendly to spare wheels. Keeping everything crossed, I think that I have solved the problem. If it returns to the car, I'll return to this thread. Hopefully some of the advice already given might be useful to other owners with rear clunk problems not involving stowed spare wheels! __________________ 2012 XC70 SE Lux Polestar 230 bhp D5 Auto Oyster Grey

Jul 31st, 2017, 14:26	#8
tt82 Forum Support Team Last Online: Nov 28th, 2022 17:33 Join Date: Jan 2009 Location: Here.... obviously!	At least it appears to be a cheap fix! __________________ The more people I meet, the more I like my dog! 2009 V70 D5 R-Design - Jeade'en

Jul 31st, 2017, 16:55	#9
Semnoz Senior Member Last Online: Nov 12th, 2023 19:03 Join Date: Jan 2011 Location: NW	I suspect my spare wheel is just as wobbly...I reckon you must be accelerating harder than I do __________________ V70 D5 185 SE Lux P3 (with rear integrated booster seats, which the kids love !!)

Aug 1st, 2017, 10:16	#10
Tatsfield Premier Member Last Online: Today 17:47 Join Date: Nov 2015 Location: Poole	I come to the XC70 from 15 years of 2+2 Coupe ownership and the muscle memory in the right foot seems to be firmly established! __________________ 2012 XC70 SE Lux Polestar 230 bhp D5 Auto Oyster Grey

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