Repetitive knock/thump when driving

JamesG1980 · Sep 27th, 2020, 08:16

Hi. The car has developed a repetitive thud/knock that appears to be coming from under the centre console area and increases/decreases with acceleration/deceleration. It’s only when the car is on the move so I assume it must be drivetrain related.

I have just replaced the steering rack on the car so the subframe has been removed/refitted The car had done about 30 miles and an MOT test with no issues since, but this noise has now appeared. Too much of a coincidence for it to not be related but I can’t figure out what it is. I’ve shimmied under the car for a quick look and can’t see anything amiss or loose.

Anyone got any ideas or suggestions? Thanks!

john langrick · Sep 27th, 2020, 12:26

Hi, I had similar with a lose (stripped) sub frame bolt. Suggest these and the lower middle engine mount bolts check?

Hope this helps

JamesG1980 · Sep 27th, 2020, 22:10

Interesting, I’d not thought to check the subframe bolts or engine mounts as I figured it was an issue with something rotational due to the speed of the knock/thump increasing & decreasing with vehicle speed.

Was the issue with your subframe bolt obvious on inspection? I will check they are all still tight but given they were all torqued up to spec I’d be surprised if one had come loose

Bashy · Sep 28th, 2020, 01:26

The lower torque mount and the hub bolt(s) can cause this, recently done both on min and issues resolved, the main cause was the hub bolt(s).

Easy to check, just remove center cap and try tightening it up....

john langrick · Sep 28th, 2020, 08:47

Hi, my noise was not rotational, It was a clunk from under the centr consol when accelerating and de-accelerating and a generally rough feel from the engine.

The nearside front (rhd) subframe bolt had been difficult to remove when my indie replaced engine. It appears the thread had been damaged. On testing, the old thread stripped out causing the noise issue and the whole bolt had to be replaced with longer and nut.

Luckily you can access the top on this bolt as the rest appear to be captive.

I was there when he applied the torque to this bolt and it was considerable!

It was pretty obvious when it was lose.

John l

Sep 27th, 2020, 08:16	#1
JamesG1980 New Member Last Online: May 11th, 2021 12:04 Join Date: Aug 2014 Location: New Forest	Repetitive knock/thump when driving Hi. The car has developed a repetitive thud/knock that appears to be coming from under the centre console area and increases/decreases with acceleration/deceleration. It’s only when the car is on the move so I assume it must be drivetrain related. I have just replaced the steering rack on the car so the subframe has been removed/refitted The car had done about 30 miles and an MOT test with no issues since, but this noise has now appeared. Too much of a coincidence for it to not be related but I can’t figure out what it is. I’ve shimmied under the car for a quick look and can’t see anything amiss or loose. Anyone got any ideas or suggestions? Thanks!

Sep 28th, 2020, 01:26	#4
Bashy Aged Member Last Online: Feb 20th, 2024 09:47 Join Date: Nov 2000 Location: Weeting	The lower torque mount and the hub bolt(s) can cause this, recently done both on min and issues resolved, the main cause was the hub bolt(s). Easy to check, just remove center cap and try tightening it up.... __________________ Regards, Bashy MY07 (56 plate) V70 Geartronic 2.4 D5 185bhp 173k, 17", full leather, an auto-dimming mirror and auto wipers are the best it can do - I have added (poorly) limo black, rear camera and parking sensors

Sep 27th, 2020, 12:26	#2
john langrick Master Member Last Online: Today 17:39 Join Date: Dec 2016 Location: Southend on sea	Hi, I had similar with a lose (stripped) sub frame bolt. Suggest these and the lower middle engine mount bolts check? Hope this helps

Sep 27th, 2020, 22:10	#3
JamesG1980 New Member Last Online: May 11th, 2021 12:04 Join Date: Aug 2014 Location: New Forest	Interesting, I’d not thought to check the subframe bolts or engine mounts as I figured it was an issue with something rotational due to the speed of the knock/thump increasing & decreasing with vehicle speed. Was the issue with your subframe bolt obvious on inspection? I will check they are all still tight but given they were all torqued up to spec I’d be surprised if one had come loose

Sep 28th, 2020, 08:47	#5
john langrick Master Member Last Online: Today 17:39 Join Date: Dec 2016 Location: Southend on sea	Hi, my noise was not rotational, It was a clunk from under the centr consol when accelerating and de-accelerating and a generally rough feel from the engine. The nearside front (rhd) subframe bolt had been difficult to remove when my indie replaced engine. It appears the thread had been damaged. On testing, the old thread stripped out causing the noise issue and the whole bolt had to be replaced with longer and nut. Luckily you can access the top on this bolt as the rest appear to be captive. I was there when he applied the torque to this bolt and it was considerable! It was pretty obvious when it was lose. John l

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