The 'E' Type Forum

Hi Chaps,
My car is fitted with the original factory power steering which I believe was from the XJ6
I have tried various valves to reduce its sensitivity with unsatisfactory results
On one occasion misplaced the drive belt and drove it without the pump behind connected
Voilà much better and not as heavy as I had thought fir slow speed manoeuvres
Question is the power rack safe to drive with pump disconnected
If I should convert to a non power rack is it a straight swap out or is the steering shaft differential as well
Your thoughts as always will be much appreciated
Nigel

This is a general reply since I'm not familiar with the detail of the Jaguar system. Assuming it's a standard system of that era, I think it would be acceptable but not desirable to run the power system without a pump, at least for a short period with fluid in the system. I say not desirable for a couple of reasons:
- you would be manually pushing the system through the seals in the rack, which would reduce feel and add effort
- you would be twisting the torsion bar in the pinion manually, which will add an amount of vagueness either side of the straight-ahead position
I can't think of a reason why you would actually be putting the hydraulic system at risk, although you would presumably be applying higher loads to the upstream mechanical parts such as the column, mounting bracket etc.
Sorry I can't be more specific, personally I would be more comfortable with fully powered or standard manual system.
Good luck

Hello again Nigel,
Reading your original question again, can you define what you mean by the sensitivity you want to reduce? Is it the textbook definition of excessive steering sensitivity - too much increase of lateral force (cornering power) for a change of steering wheel angle? If we can confirm the problem I might be able to suggest a way to reduce the concern.
Regards
Clive

Question is the power rack safe to drive with pump disconnected

I think the general view on cars is that you shouldn’t drive them any distance without power assistance if the rack is designed for that due to the strains imposed. Having said that i had a power steering hose burst just as i was leaving for a 500 mile round trip to Wales, so I just drove there and back with no power steering. Didn’t cause any damage - but it was a Mondeo

I would look further into whether a non power steering rack would be a not too challenging swap

Hi,

Thanks for the interest in the post.

The problem as such is no doubt down to my personal preference.

The steering is a marvellous asset when parking especially as I have 6 inch rims/ 205s fitted and a 15 inch version of the original steering wheel from Moto Lita.

But once on the move and negotiating winding passes and hairpins it is too light with little in the way of feel and on unexpectedly tight bends feels as if the steering is over reacting to input.

I have tried a reduction kit available from a well known UK supplier which although supposed bespoke required pipe adapters and was a disaster.

Indeed a hydraulic specialist shook his head at and am working with him come up with a solution to reduce the power/sensitivity of the steering using two hydraulic valve ( Flow Reducer/ By pass return to the pump) but in doing so would this unduly fatigue the steering components if power steering force was sufficiently to my liking: if such power reduction was never factored into its original design ( to make XJ6s and 'Heavy Chevvies' Rolls etc more manageable would the safest and easiest option be to remove and mothball the system and retro fit a manual rack.

Decisions......Decisions.
The car is an orignal UK RHD by the way fitted with the P/S option.

IMO the proper method to increase the effort is to increase the spring effort to open the valve
Changing the hydraulics is, IMO a poor bandaid.
Tom

I’ll offer some general comments, prefaced with the fact that I’ve never driven an E-type with power steering. On the other hand I spend over forty years working on car development, primarily chassis systems with a lot of time specifically on steering systems. I don’t have detail of the Jaguar system but from pictures it looks quite typical of hydraulic systems of that period – driver torque at the steering wheel turns the pinion, which is “waisted” to a small diameter so twists slightly to open holes in the surrounding valve, admitting pressurised fluid to the rack where it adds force to supplement the driver input. If that's substantially incorrect then what follows will not be useful!
There are typically three variables in this:
- the diameter of the torsion section of the valve. This determines the force required to open the valve, that is how early in a turn the driver effort is supplemented by hydraulic pressure. (Whether the force vs angle chart is a U or V shape).
- the size and position of the holes in the valve. These determine the rate of rise of assist force, that is the shape of the U – does it have square or rounded corners?
- the flow characteristic of the pump. Later systems (perhaps 1980s on) included some mechanical or electrical control to match the flow to road speed rather than engine speed, to give a more natural feel and mask steer effort variation through (say) a gearchange.
The first two use sophisticated machining, I wouldn’t try to modify them unless I found a direct replacement valve assembly, which would require some specialist knowledge. The flow to the rack would be easier to modify, either with a different pump or some kind of flow control device, but…if the torsion bar is too small for your taste that will still be the case. You’ll still have a “loose” or perhaps “nervous” feeling around centre, although the effort moving away from centre may be usefully increased. I’m guessing the E-type had base parts in common with the higher volume Jaguar saloons, so the chances of finding a sister part which would move the effort in a more sporting direction are probably not high?
You might try external means to increase the apparent steering effort – an obvious route would be to increase the castor. The original spec is unusually low, increasing it to 5 degrees would give the steering higher centre definition feel and more effort build as you go into a turn. In theory also better high speed stability and a slight gain in front cornering power.
If you modify the system to include non-Jaguar parts please be aware of the possibility of “catch-up”, an unpleasant condition where the assistance can’t rise fast enough to support a sudden demand – a fast swerve to avoid a sudden road hazard, for example. It shows as a sudden increase in steering effort as the assist temporarily falls away, and can be very alarming in a stressful situation. I’m sure the original system would pass the test, which has been an industry standard for decades. I would be less confident about aftermarket systems, where the pump or hoses might not have sufficient reserve capacity for a sudden step increase in demand. Even more so for supplementary electric systems. There’s a simple check – in a safe, deserted area, apply about 90 degrees steering lock fast and remove it equally fast to simulate a lane change. Not a high speed test, low speed is more demanding and safer. It can sometimes be found in a parking manoeuvre. Please be careful – I once rolled a car when the assist dropped away faster than I could supplement it with muscle power. Knowing this condition exists will not solve it, but you’ll be somewhat prepared if you have to do an emergency lane change.

Thanks for all the advice guys.
I will keep it as Jaguar intended and may try a smaller steering wheel or change over to a manual rack if I cannot live with it.

Retroman wrote: ↑

Tue Jun 28, 2022 9:55 pm

try a smaller steering wheel

I did this on my XJS and it was surprisingly helpful.

You don't get an improvement in the "dead" feel but it makes the steering heavier and less "floaty" at speed.