As the title says, I have developed an irritating front end knock/clunk when driving over any sort of uneven surface and here in Ireland we have many such uneven surfaces, but we call them roads!

Anyway, apart from track rod end ball joints, lower shock bushes and upper shock foam type isolators, those yellow things that go beneath the top nut, what else should I be looking at?

Shocks themselves? The knocking seems to be coming from the passenger side (RHD) but naturally I want to replace anything suspect in pairs.

Any thoughts much appreciated.

 

Front knock on my X300, XJS and Lincoln LS were my sway bar bushings, seemed tight by hand but changing them did the trick. YMMV

 

+1 sway bar bushings.

 

Meh, with all due respect...-1 sway bar bushes...I renewed mine, didn't quell the knock. Neither did new shocks and bushes.
I've had a muffled thump somewhere forward for 3-4 yrs now. One of these days, given time and gumption, I'll find it and mend it....unless it self-identifies first!

 

Many thanks for the responses guys. By "sway bar" do you mean anti roll bar? That's the long heavy bar running crossways between the front wheels and has a pair of rubber bushes on the mounting clamps? Europe and America seem to have a different name on almost every part of a car/automobile!!

My knock is very much that, a clear knocking sound, just like you'd get from badly worn shock bushes, as opposed to a "muffled thump" but I will investigate further and let you know how I get on.

Thanks again.

 

Yes, it's the same thing. The bushings are inexpensive and easy to change. They almost always need to be replaced because they are easily overlooked. That doesn't mean your knock will be eliminated that easily, but it's a good place to start.
I recently replaced the upper shock bushings which were noisy. This is another easy and inexpensive job.

 

Not so much a knock as a clunk as radiator under cradle (I think) connects with speed bumps - would love to know how to rectify that

Thanks

c

 

The rubber bushes that go under the radiator would fix that particular knock, and check the bushes under the air conditioning condenser as they can disappear too, which leads to a leaking condenser in fairly short order.
As for general front end knocks, the anti roll bar bushes are inexpensive and easy to change, ditto the upper shock bushes. The lower shock bushes are slightly more difficult to do, but not hard. You will almost certainly feel a benefit from renewing these bushes even if it didn't sort your knocking.
On a cautionary note, I wasted a lot of time looking for a front end knocking as I refused to consider the lower shock bushes, having replaced them only 8000 miles earlier. When I eventually checked them properly, they were shot! They were aftermarket parts from a well known and otherwise reputable supplier. More expensive Jaguar parts now fitted, and still good 15000 miles later. Same thing with lower ball joints. A fraction of the Jaguar price, finished in 10000 miles. It seems you get what you pay for after all!

 

sogood,

In my experience, the most common cause of front end knock on one side has been the upper shock bushings. The ones on the left hand side of the car seem to go first due to their proximity to the hot coolant reservoir. Since you're using the OE style yellow foam bushes (which I strongly prefer myself), you can't assume they are OK if they are more than a few years old.

One simple way to check for your left side knock would be to jack up the front left corner so the wheel is off the ground and the suspension is hanging free. Look into the wheel well to see if there is any space above the metal cup washer atop the yellow foam upper shock bush and the underside of the fender well. Here's an example of a gap that caused a knock on our '93:


You can also feel the yellow foam to see if it has hardened, which may indicate that it is no longer capable of functioning properly.

There are some some additional upper shock bush photos at this link:
Welcome to Jag-lovers - Members Photo Viewing Page

Cheers,

Don

 

Thanks for the input guys. I did replace the upper bushes and lower shock bushes, but the problem persisted. I removed the sway bar bushes and they "seem" to be sound and strong with no obvious wear, but I will replace them with new ones. I also ensured that the brackets that hold these bushes were good and tight. I also checked the tightness of the steering rack, which I've read, can loosen over time. All good.

I also did the inspection as suggested by don and while there was a visible gap at the top of the shock, like in the photo, tightening this up didn't make any difference either.

I'm thinking that maybe new shocks (and new lower mounting bolts) is the way to go. I can't think of too much else that might be responsible, apart from something mechanical etc. totally unrelated to suspension.

I will keep you all updated and thanks again for the help.

 

Hi sogood,

How did you tighten up the visible gap?

Cheers,

Don

 

I lowered the car back onto the ground so that the weight/tension was off the shock and the gap naturally closed up and then I tightened down the top nut on the spindle, (holding the spindle to stop it turning). There was a fair amount of tightening to do before the top nut tightened up fully. I also did the opposite side while I was at it.

Assuming this is the way to go? Thanks.

 

Did it alleviate the knock?

 

No change as per above. I think new shocks are called for. Any recommendations on a good brand to use?

 

Did the shocks show any signs of being likely to knock when you had them off to do the lower bushes? Depending on how old they are, there might be some merit in changing them, but I would be surprised if your shocks were causing a knocking. Are you happy with your lower ball joints?

 

Did you jack up the car again after you tightened the shock top nuts to see if you still have a gap when the suspension is hanging down by the weight of the wheel and force of the road spring? Any gap at all will produce the knocking sound. Here's what you should see if your bushings are healthy, no gap at all and the bushing still soft and pliable:




Cheers,

Don

 

I also had a knocking sound for a while. I opened the bonnet to see how the conditions of my upper shock bushings are.

Not good I can tell you haha, they are no where to be seen. Only evidence I can find is the dust that gathered below. ;-)

Today I replaced left and right upper shock bushings with new ones.
Very easy job, done in no time.

I was surprised to find that the right assembly did not include a spacer tube to hold everything nicely in the middle. I ordered it from the local dealer for 3 euros, not a big deal. This part missing must be crucial for maintaining the bushings, probably also the reason that the right bushings are missing completely.
I also noticed that the previous owners did not assemble it correctly, how can you screw that up I wonder.



Bushings are completely gone on the right side due to a missing spacer tube




New Bushings in place, time to lower the car.




old bushings with the new spacer tube.

Fitted some new Pirelli P-zero tires on the back, the car drives so smoothly now and no more knocking sounds ;-)

- Maraud

 

Many thanks for all the input folks. I've ordered a bunch of replacement parts which won't do any harm either way. Shocks, bushes, isolators, anti roll bar bushes, track rod ends etc. etc. She's due a bit of loving.................

Regarding the spacer tubes, I didn't see any such part when I was poking around but it shows up in the parts diagram as part no. MMB 2154AB but wasn't available. So, I'll have a look around and see if I can source them.

Thanks again and I'll keep you all updated.

 

If you can not find them, i'm happy to sent you some. I have one left here, but to order more is not a big deal. Let me know!

 

Many thanks for the kind offer and apologies for the delay in responding. I was away from home working and returned yesterday and today, my shopping list of new parts arrived. The spacer tubes in question came with the replacement shocks, along with new upper spring isolators.

So, tomorrow she will be given some time and attention. I'll keep you updated with how things go and thanks again.