XK 2011 knocking on full lock

[stuartsmall21]

Hi, I have a 2011 5 litre coupe. When I pull out of my parking space at work, I go full right lock. It’s as if the tyre jumps/slips and there is an audible knocking sound. I’ve just had the pads done, and that has helped, but the noise is still there. Discs have plenty of meat on them. Any ideas what might be wrong??

[mike020150]

To the best of my knowledge, these symptoms aren't a common issue. So, I think you will have to go back to basics to find the problem. First check the front tyre wear pattern. Severely misaligned steering gear could cause a 'jumping' effect and a heavy wear pattern would give you some clues. Earlier XKs with the larger brake discs could create noises when front wheel bearings started to wear. The movement in the bearings allowed the discs to touch the brake back plates when cornering/turning loads were present. There should be absolutely zero endfloat in an XK front wheel bearing. So, check your car's wheel bearings. Then, move on to checking the front suspension and steering ball joints for excessive movement, not forgetting the anti-roll bar bushes. Shock absorber top bushes and security of fixings should also be included in your checks. If all the above check out as safe and unworn, it's just possible that internal damage/wear of a shock absorber could be guilty of producing a knocking noise. Mike.

[Astromorg]

Can you identify which end the noise comes from? I ask this because when you're turning on full lock, then the differential is brought into action and could be feeling the large difference in rear wheel rotation that full lock will cause. Which diff do you have - passive or electronic active?
If one wheel, is having to 'catch up' with a jump, then an assistant should be able to identify which wheel is doing it for a starting point, but as the rear wheels are linked via the diff, that could be relevant.
As an aside, I occasionally experience a similar front wheel jump in my AWD X Type when on full lock and passing over a low friction surface such as the grill over a rain gutter. It's always done it since new 85k miles ago. I have to admit not pursuing it as I've always assumed its a release of a bit of wind-up in the AWD system while on full lock.

[Jhdee]

Have a look at the power steering fluid level. Had similar on my previous 4.2 XK which had a slight leak. When the fluid dropped below a given level the steering would "judder" (for want of a better description) on full lock.

[J44EAG]

That got me thinking...

A worn or cold drive belt can slip and cause momentary loss of PAS pressure. Similarly a weak automatic belt tensioner, but perhaps an unlikely issue given the relative newness of the model. Certainly though, Jaguar had occasional cause to increase belt tensioner spring pressure on other models.

Mike K