As some of you may trawl the forums as much as I have you may seen some of the problems that I have had with my XJ. I have recently had a new prop centre bearing and gearbox service to try and fix a vibration and a noise. Well the noise I had of a whirring has gone the bearing fixed that but I still had an odd vibration in the car at certain speeds. while trying to find the fix to my noise we found that one of my alloys was bent causing a shake, the fix to this was to put the spare on then the vibration changed. Well today got the car to a good friend of mine to have a look with me at what is causing this vibration well oscillation through the body of the car that starts at around 47mph upwards.

The first thing was wheels they were all run out and found to be perfect apart from just need slight balancing. The tyres also appeared to be in very good condition no high spots and a good Pirelli spec with high tread left on them. Next the car was in the air and one by one each bush was pulled and pushed with nothing showing any signs of wear(as I have replaced sway bar upper controls and others the last few months).
The car was then taken on a test drive on straight motorway (highway) at 50-80mph and what we found was that the problem seems to be engine related but not a tight rpm window related. In other words at certain speed anything above 2000RPM the car has this slight shake. We parked up idled and slightly revved the car and got the same vibration through the steering wheel but at a finer window of rpm.

So basically has anyone else had anything like this I mean I don't think that the engine mounts are on the way out due to it only being a small rpm window when the shake happens. Is it possible that one of the power steering lines is touching the body and at set speed is oscillating just right to be noticed.

 

What model of X350 and what size are the wheels ?

I think it is now well known that Jaguar boobed in a fairly big way with the suspension on these cars as it is noticeably harsher than previous models, and lots of people complain about vibration and harshness, especially if the harder 'Sport' air springs are fitted, like I have on my car. I took my car to a specialist who I trust and was told it was 'normal' for this model. I am planning on replacing the air springs with the 'Comfort' type, but the cost is so large, I have to wait a while.

 

Fraser,

What do you mean the 'comfort' type?

 

its a 4.2 2003 with 60k on the clock . I don't find the ride harsh at all I have the 18 inch luxury wheels with the chunky Pirelli p6000s and I also have the comfort suspension. the car floats on the motorway just bloody vibration that goes with it, it really is the most comfortable car I have owned makes my old lexus look like ford fiesta.

 

Air springs on the X350 are of two types, 'Sport' and 'Comfort'. Sport are fitted on the cars with the 'Sport' label, plus the XJRs. My car is a Sport and I find it a bit too harsh, to be honest, so when I get the opportunity, I am going to swap them out for 'Comfort' units. I shall then sell the old ones on eBay, as they are still working OK. The only difference between the two types is the Comfort ones have a bigger air chamber.

 

Is there any chance that my steering rack may be at fault, are the bushes available for this. Was just thinking that the vibration is through the steeringng wheel when stationary at a set rpm but the engine is fine eg not missing ect.