Steering fault - jerky

A steering problem has become apparent in the last couple of days on my '83 HE (rhd).

When driving slowly to turn a corner, rotating the steering wheel is no longer a smooth action, so much so that the wheel stiffens up and then ‘jerks’ after which it continues on turning smoothly. This effect occurs within a 1/2 to 3/4 turn of the wheel from centre, in either direction.

Then, as I drive away on the straight and wobbling the wheel left and right a couple of times, the stiffening effect disappears and a smooth movement takes over.

I have also observed that with the car stopped and in idle, the steering gear assembly moves slightly left and right about 5mm as the steering wheel is rotated. I assume the mount bushings are failing?

I’ve also looked at the lower universal joint while moving the wheel but cannot see any looseness or judder when the wheel passes through the ‘jerk’ point, as above.

I’m guessing there could be a number of reasons causing this problem - any advice would be helpful and appreciated.

Thanks
David

David,
It sounds a lot like your power steering rack bushings need replacement. This is a very common problem as these cars age. If you are handy, have the tools, and the XJ-S Repair Operations Manual this can be a DIY job. I have replaced those bushings on my XJ6s, XJ12, and XJ-S over the years. Please check that your power steering reservoir is properly serviced. What are the date codes on your tires?

Paul

Paul,
Thanks for your suggestions. Yes, the bushings certainly need replacement - they are soft under the fingernail!
The power steering pump was replaced with a refurbished unit 4 years ago and new tyres, also 4 years ago. Run 15000km since then.

Great hobby car, this one! Have done many fix-ups over the 20 years since I purchased it.

I’m also considering doing a rebuild of the steering rack assembly. The full history, which I have available, does not show that this has ever been carried out previously, except for replacement of the tower seal which has been done twice in the life of the car. There are signs of minor leakage on the bellows. Fortunately, rack seal kits are still readily available.

What I can’t understand is, what would be the ‘mechanism’ that would cause the stiffening up of the steering wheel, followed by its release (jerk effect)? Could it be related to sticky or worn seal, fluid blockage, etc, within the rack assembly? Or, perhaps something to do with the steering column components?

Perhaps I should just do the bushings first and see what happens?

Any thoughts?

cheers,
David

Don’t forget to check that the p/s belt is tight

Cheers
DD

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Thanks Doug.
Yes, have checked that the belt is tight.

Another thing I’ve noticed - when the wheel is turned to almost full rotation (normally no need to do this anyway), a ticking noise can be heard coming from somewhere. I assume this is a pressure release valve and probably a normal operation. Anyway, still to be investigated - not sure whether it’s from the rack assembly or the pump.

cheers,
David

Jerky steering is often due to the power steering pump sucking in air, either due to low fluid level, or an air leak into a suction pipe.

I’m assuming the Jaguar power steering pump has a directly connected reservoir, so an air leak would seem unlikely, but if it has a remote reservoir, then check the unions are tight.

You have two problems here. The left to right movement are most likely the rack mounts or the bonded rubber washers that are supposed to be on either side to limit movement. As far as the lack of assist or the assist jerking on and off when cold, there are nylon rings in the head of the rack that relax with age and do not seal until warm. As time goes on, it takes longer to warm up and seal. Towards the end of the Adwest racks, Jaguar came out with nylon rings that had a metal expander on the inside so they would seal better. Google " power steering morning sickness". It is not just a problem with Jaguars. Both of these problems should be solved with a properly rebuilt steering rack. Below are pictures of the newer style ring sets.
Rack13

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Dick,
Thanks for your comments. Yes, I note that one of the Rack Seal Kits on offer on ebay for the XJS with VIN greater than 104775 includes those rings you have shown. The kits is specified as Jaguar Part Nos: JLM10834 & AEU1432

I’m still looking on the web for instruction details for doing racks which these seals will fit.
How do I recognize an Adwest rack or perhaps a later model which I may have in my '83 XJS, VIN 112036?

Dick,
Further to my last reply to you, the rack diagrams I have for reference are;
Haynes Jag/Daimler Workshop Manual, page 274;
Jag XJ-S Repair Operation Manual, page 57-1 and on…

There should be a plate riveted on the rack facing towards the rear of the car. It’ll say Adwest on it. Put the car on jack stands, crawl under, and take a look.
All of the racks until sometime into the facelifts were Adwest. An 83 would have come with one.

Jon

Steering rack support bushings.i changed mine to polyurethane…got kit from John’s cars in Dallas and the tool to do it with…30 minutes to install

Adwest racks have a steel tube (body), ZF have an aluminum body. Easy to tell with a magnet.