Technical Knocking sound worse

[Nicky Swans]

So yeah, I posted before that there is a knocking sound coming from the engine somewhere. Now it is about 50x worse it is very loud (enough for people to turn in the street) and it only knocks when the foot is off the gas, clutch and brake, so when the car is rolling by itself it makes a knocking sound but as soon as the brake is applied it stops instantly. Also can not be heard at 40+mph and sounds terrible from start 0mph to about 30mph.

The front wheels have also started screeching when they are turned quickly/sharply which could be the bearings? I am going to Costa Del Sol Sunday so quickly need the problem diagnosed so parts/arrangements can be made while I am away.

Cheers.

 

[CF MJ]

iif it sounds like a rattlign kind of noise check ur heat shield it might be that as are one is loose on my Gfs car and man its horriable keep meaning to remove it lol

 

[Nicky Swans]

Anyone else able to help with this? Sounds even worse after I come back from holiday.

 

[x Alex x]

i'd say wheel bearings, the ones on my mondeo seemed worse after it had stood for a week

 

[Mr Wild]

Could be the brake caliper itself or a warped disc? Could be a loose exhaust or loose heat shield on the rear of the exhaust?

 

[Nicky Swans]

Could be the brake caliper itself or a warped disc? Could be a loose exhaust or loose heat shield on the rear of the exhaust?

Would the knocking sound really stop if it was the exhaust when the brake is just gently touched? That is what happens

 

[RB2009]

hi, did you check the driveshaft? any movement in them wil be more apparent when coasting because when under load any movement is taken up, whereas when coasting the shaft isnt being held against the CV joint so its free to move backwards and forwards creating a knocking sound. Sounds like worn CV joints to me, or failing that a differential problem in the gearbox.

Wheel bearings, and warped disks etc are rotating exactly the same regardless of if foot is on the throttle or not so they noise would be apparent all of the time. Same with the heatshields, if loose its state would be exactly the same regardless of whether accelelator pedal is pressed or not. Also while over 40mph the car has more momentum again probably taking up any slack.

best way to diagnose would be to jack the front wheels up 1 at a time, firstly put it in gear and move the wheel back and forth to check for movement in the shaft and cv joint.. then take it out of gear and rotate it, then put the wheel on full lock and do it again.

 

[Nicky Swans]

hi, did you check the driveshaft? any movement in them wil be more apparent when coasting because when under load any movement is taken up, whereas when coasting the shaft isnt being held against the CV joint so its free to move backwards and forwards creating a knocking sound. Sounds like worn CV joints to me, or failing that a differential problem in the gearbox.

Wheel bearings, and warped disks etc are rotating exactly the same regardless of if foot is on the throttle or not so they noise would be apparent all of the time. Same with the heatshields, if loose its state would be exactly the same regardless of whether accelelator pedal is pressed or not. Also while over 40mph the car has more momentum again probably taking up any slack.

best way to diagnose would be to jack the front wheels up 1 at a time, firstly put it in gear and move the wheel back and forth to check for movement in the shaft and cv joint.. then take it out of gear and rotate it, then put the wheel on full lock and do it again.

(Would the drive shaft failing also cause the car to pull slightly when braking to one side?)

 

[RB2009]

Not necessarily, but this could be a separate issue.

Warped discs would cause it to pull slightly all of the time, and wouldnt knock so much, but would cause a binding sound as the disk will rub the pads on each revolution.. can also cause squeeqing.. but not knocking.

Other thing it could be, which would cause pulling to one side is any kind of movement in the suspension struts.. through eigther damaged top mount/bearing, and any rubber bushes.. as under braking the whole lot would move.