My newly aquired 1998 XK8 (57000 miles UK car) is quite frightening when cornering at speed. Say 70mph on a dual carriageway. I can turn the wheel a tiny amount to start the turn but the car will try to swerve into the bend. I have to back off the steering wheel and end up taking the curve in a series of swerves. Changing lanes on the motorway is done very gently.

I have checked all the tyre pressures and noted tyres are wearing evenly.
I have flushed out the power steering fluid and replaced the high pressure hose from the pump to the rack. There are no knocks or rattles from the front or back. I jacked the car off the ground and could not rattle any of the wheels or find any play anywhere.

I have disconnected the plug with the two wires to the steering rack. The problem persisted. The steering was stiffer at low speed. No improvement at high speed.

I have removed the 5 amp and 20 amp fuse from the adaptive suspension. The ride was somewhat more bumpy but the problem persisted.

I have disconnected the battery earth. Switched on the ignition and touched the disconnected earth to the positive terminal. I think this helped but not completely. (The mirrors and key fob started to work though).

I have ran out of ideas! Can anyone help? Thanks.

 

Do ypu still have the anti roll bars installed?
Both back and front

 

Yes. Good thought. I have just jacked the car up to have a specific look. A big anti roll bar on the front. A small one on the back only about 18 inches long. All looking original. I could not see any signs of play anywhere.

 

Assuming there has been no previous accident damage which may have resulted in misalignment, have you checked front Crossmember Bushes (item 2) and Vee Mounts (item 3)



and rear suspension subframe bushes (item 13) are intact?



The Vee Mounts can leak or even break up. Steering Rack mount bushes can also fail allowing the rack to move laterally.

Graham

 

Thank you for the ideas. Items 2, 3 and 13 all checked. I lifted the car right off the ground & could not see any significant deterioration on any of the joints. Nor any others. I also checked the steering rack mounts which were tight and the rubbers looked sound.

As the car was off the ground with all the wheels fitted I pushed the front wheels from lock to lock. The resistance was quite uneven going to almost nothing at full lock. I tried it a few times but then the reservoir overflowed. All the oil must have been pushed back into it so some air may have got into the rack? I also noticed there seemed to be a lot of dirty oil on the hoses that lead to and from what I think is the steering oil cooler behind the front grill. As an aside (and probably unrelated) there was also a green sticky fluid running down the left hand side of the front (air conditioning) radiator from top to bottom. I have no idea what that is, Dexron iii is red as is the antifreeze & air con refrigerant should evaporate?

I gave the back wheels another good pull about & just managed a tiny clunk if I pushed & pulled the top of the wheels. I believe this is rear wheel bearing tolerance.

 

Nothing coming adrift from front or rear suspension is good news and eliminates this from your search. Slight play on a rear wheel bearing wouldn't cause the extreme steering effects you're experiencing.

The power steering action sounds very odd. It should be smooth from lock to lock and this could well be the cause of the handling issues on cornering.

As you'll already have seen, there's quite a lot of plumbing around the rack. This diagram should help identify the relevant pipes:



The bleeding procedure is as follows:

1. fill the reservoir to the bottom of the filler neck
2. allow any air to escape (bubbles stop rising)
3. top up if necessary
4. raise the front of the vehicle and support it on stands
5. do NOT start the engine, turn the steering from lock to lock three times
6. start the engine, immediately top up with fluid if any air is expelled
7. turn steering from lock to lock three times
8. switch off and lower vehicle
9. top up reservoir to Max mark on the filler cap dipstick
10. refit filler cap

There should be no loss of fluid from the rack boots.

If bleeding doesn't resolve it, the pump or rack are the next suspects.

Graham

 

Was the engine running when you did the lock to lock test?
What does the resistance feel like if you turn the steering wheel lock to lock with + without the engine?

 

Have you had the alignment checked?

 

Do you have the correct size tires on the car? I once had bigger tires than normal on the back and my heart skipped a beat on the highways when changing lanes with severe tramlining.

 

Check the tie-rod ends AND those sway bar end links...if the car is lifted, you'll need to take some pressure off the links by supporting 90% of the weight of the wheel...easisest way to do this is jack it up on the floor, get a jack stand under the body, of course, then jack up the tire/wheel...that reveals much of the potential play in those areas.

Use a prybar and 'test' the effectivenss of the bushings in both the upper and lower control arms...oh yah, and the upper A-arm above the rotor...all are deteriorated in about 7-8 years, and affect handling dramatically if they are allowing movement.

 

Thanks Folks.
I have blead the steering exactly as described. With the engine running the power steering felt much better when I pushed the wheels from lock to lock. I think that by pushing the wheels from side to side with the engine stopped I must have sucked air into the system.

Tyres are Perelli 245/45/ZR18 96Y on the front, fairly well and evenly worn. Haida 255/45 ZR18 103WXL on the back almost brand new. They replaced Perellies on the back which were the same size and had also worn evenly. The rotation is correct.

The tyre wear and the lack of physical damage or other problems leads me to thing allignment is OK.

I have not checked the rubber mounts with 90% of the car weight on the wheels. I will try to do this next week.

I took the car for a spin today on the motorway and some twisty A roads. It seemed fairly well behaved most the time and I felt it wasn't trying to kill me. On fast twisty stuff the car still felt a little too dramatic, tending to sway from side to side. I would have expected such a car to feel it was on rails!

I'll report again after I have double checked all the bushes again. Are there any others should particularly check in addition to those in the diagrams above?

 

Good to hear the steering bleed has made some improvement.

On the front suspension, you should check



1. upper wishbone bushes (circled in red)
2. lower wishbone bushes (circled in blue)
3. ball joints (circled in green)

The upper wishbone bushes (1) are the fastest wearing items. Some prefer to use aftermarket Polybushes. These last longer but are less compliant.

Graham

 

A car (especially a high performance car) can suffer from unpredictable handling when tires with different characteristics are fitted front and rear.

 

That kind of assumption can lead to a great deal of wasted time.

Twitchy behaviour in corners is associated with excessive toe-out.

Racers deliberately use toe-out to setup for corners faster. It is seldom desirable for use in normal driving by drivers who are not expecting it.

 

Another evening under the XK8. I suppose it's better than television.

I measure the toe in as the car sat on the ground using two parallel pieces of string, one each side of the car at hub level. I measured zero toe in for the front pair of wheels and 2mm toe in for the rear pair of wheels. (0.0 degrees and 0.25 degrees front & back respectively) I understand front toe in should be 0.2degrees +/- 0.2 and the rear should be 0.3 degrees +/-0.2. Therefore the front is just on the limit and the back is about perfect.
I did not attempt to measure cambers and castor angles etc. Presumably this is something a specialist needs to do? Is a jag dealer the only way forward here or can any tyre supplier check tracking & maybe other bits & pieces.

I also jacked the car up again and checked the wishbones top and bottom and the ball joints again with weight on and off the front wheels and with the front wheels on and off the car. No defects found unfortunately. I used a large screwdriver to lever bits about where could but didn't want to break the delicate looking aluminium bits. I was a little suspicious of the joint at the bottom of the shock absorber/suspension strut. The dust covers looked a little damaged and I think I perceived a little vertical movement in the RHS one but couldn't get it to move when I went back to it to check.

 

Steve,

An excellent critique of this evening's TV programmes.

Any of the major UK Tyre Depots (e.g. HiQ or national Tyres) will be able to check steering geometry for you at considerably less cost than the Jaguar Dealer.

If you can post pics of the suspension and dampers, many here are used to seeing and repairing these parts and will get a good idea just from the appearance where any problems may lie.

Graham

 

What happens to toe at the front if you push the fronts outward first?

One of the techs here *always* pushes out the fronts during measurement/adjustment because as the car rolls down the road it will tend to toe-out. So, zero is going to be more than zero in motion. A zero or a small amount of toe-out will give you low scrubbing wear, but will feel twitchy as previously described.

There is a method of measuring toe using two lasers projected forwards described in a previous thread. Very accurate because the distance enhances measurability.

 

[QUOTE=s.williams815;605759]
I measure the toe in as the car sat on the ground using two parallel pieces of string, one each side of the car at hub level. I measured zero toe in for the front pair of wheels and 2mm toe in for the rear pair of wheels. (0.0 degrees and 0.25 degrees front & back respectively) I understand front toe in should be 0.2degrees +/- 0.2 and the rear should be 0.3 degrees +/-0.2. Therefore the front is just on the limit and the back is about perfect.
QUOTE]


I was told that this method can not be used on the XK8 as the front and rear track widths are different.

In the end I bought one of these Gunson | Easy Wheel Alignment with Laser Beam Accuracy

 

Does the car swerve on both left and right lock? Or just one way?

 

I am not going to even attempt to claim that I am a mechanic, but I am just going to add my 2c..

s.williams815 wrote: I can turn the wheel a tiny amount to start the turn but the car will try to swerve into the bend.

Would this not point directly to the power steering. My XK8 has what I would call "variable steering," which makes steering easier on slow speeds versus open road. If the steering is acting the same on the open road and slow speeds, would that not cause the effect s.williams815 describes?