Do I need a new steering rack?

XJ
1

I have a 1971 series 1. The rack was replaced by the PO about 8,000 miles ago - a “Pow a rak” unit bought from one of the usual Jaguar suppliers and fitted by a local garage.

The symptoms are:- a slight vagueness in the steering - constant small corrections needed at the steering wheel when driving at moderate speed round a gentle curve; when stationary at tickover a vibration can be felt by hand at both road wheels when the steering is being turned and the steering wheel “snatches” as if the gear is sticking or fluid pressure is rapidly varying; the symptoms are worse with increasing steering load such as when steering under heavy braking or parking nose downhill. I can feel nothing unusual when turning the wheel with the engine not running.

I am reluctant to suspect the rack because it is relatively new. The pump is original and I replaced the fluid and pressure hoses recently. The bushes and ball joints are old (except the rack bushes), but I can’t see any significant wear or looseness. The only other peculiarity I can find is that the “air transfer tube” at the front of the rack is a little loose, but I don’t know if that is critical or relevant,

Any guidance would be very welcome.

Frankie

2

Check belt tension for the PS pump and the fluid level in the reservoir.
Carl

3

Fluid level correct by reference to the “cold” mark on the cap/dipstick.

Automatic belt tensioner functions, so I assume OK. The tensioner “bounces” quite a bit when running but I can’t see that affecting the pulley rotation - no squealing to suggest belt slippage.

Frankie

4

The vagueness in the steering is usually caused by the pin in the top of the pinion getting loose. This pin centers the internal torsion bar to center the rack back to neutral. When loose, there is a good bit of play. The Snatches are usually caused by the pinion seal rings. There are 4 of them. Jaguar initially used standard nylon rings. They can be replaced with “engerized” rings which have a metal expander ring on the inside to push the nylon out so it seals better. Most likely, a proper rebuild will correct your problems.

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5

You might check to confirm that the new rack bushes are doing their job. Look at the rack whilst turning the steering wheel back and forth–any slop in the bushes?

6

Hi Dick - that’s very interesting. I have now read your piece on Jag rack interchangeability and might try doing a rebuild myself, particularly as the exchange rack from the specialist supplier has not stood the test of use.

The rack presently in the car is the later one (C39262), which the PO fitted as a replacement for the original. UK suppliers list several rebuild kits for the S1 racks:- JS726 AAU1503 JLM10834 11983 and 12715. Before I call up and quiz them for the energized rings and kit compatibility, do you have any particular suggestions for a kit supplier? I assume that tightening the pinion pin will be straightforward once I open the tower and see how it is installed?

Frankie

7

For the Series 1 XJ6, there are three different rack kits depending on the rack. From the part number, I will assume it is a RHD rack. The LHD rack in that range is a C-39263. I do not know of a rack kit for the early racks that contain the engerized rings as they were not put on those racks originally. On the head of the pinion, we replace the seal inside and use a taper pin after reaming to fit. The seal in the top is an o-ring size 011. Not usually supplied in the kit either. The head will need to be flowed and centered after this so it has neutral steering. Otherwise, it will tend to have assist to one direction even when the wheel is not being turned. Good luck with it.

8

No - the bushes are tight.

F

9

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Have you checked play with a crowbar, Frankie - and indeed have you checked for play with front lifted …?

Vagueness in steering usually denotes slack ‘somewhere’ - and with only 8000 miles on the rack and the bushings tight, I’m equally reluctant to suspect the rack…

While wheel alignment with slack of any kind present is pointless - it will certainly reveal any slack that may otherwise be undetectable. Wrong, or varying, toe will have the same symptoms as described - steering inputs may be required as a result of this rather than arbitrary inputs from the rack itself. And slack in the camber/caster may also have some influence…

That said; do not forget the possibility of ‘rear wheel steering’ - the problem may be at the rear, even low tyre pressure would affect car behaviour…?

Frank
xj6 85 Sov Europe (UK/NZ)
**

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10

That was my initial reaction too. However, another symptom is vibration though the road wheels with the car stationary and nose heavy (pointing downhill) and the steering wheel being turned with engine idling. You can feel the vibration with your hand placed against the road wheels - a bit like driving over rumble strips - and at the same time the steering wheel “snatches” back and forth quarter of an inch or so at the rim against the motion of the slowly turning steering wheel. That persuaded me that the issue was hydraulic and to rule out any bushes except the rack bushes (which I know are good).

In a couple of months I will be replacing ALL the front subframe bushes and joints - to do that the rack has to come out anyway, so opening up and inspecting/replacing the seals and pin Dick refers to will be part of the job. The rear subframe was rebuilt earlier this year.

I will post a conclusion when the job is done (and the problem hopefully cured).

Thanks for all your help.

Frankie

11

The folks that have posted have superior knowledge as to these cars than I.

I do not recall the belt drive as it existed in my car when DOHC powered. I do recall the method of belt adjustment. Slick, a n adjustable rod. More elegant than the slotted braked of USA cars of old. Although my son markets a custom bracket. He makes them on his enhanced CNC mill

But, a floating adjustment!! My LT1 has that. And, it does not “bounce”. Back to slipping belt. the simplisit of flaws and the easies to fix.

My axiom, the easies first.

Carl

12

I have the Service Manual for the Series 1; PM me and I will send it to you - not all of it, it’s too big to scan; but the bit on the Power Steering.

13

Thanks for the offer Mark but I have the SRM (publication E.155) for the S1 and read through the section on the PAS. A lot of helpful info there, but couldn’t find specific reference to my symptoms.

Carl raises a point I hadn’t thought of before - why is there a spring loaded tensioner for the PAS/water pump belt and not for the alternator? I’ve no idea! But I still can’t see it is the cause of the problem (no belt squeal).

F

14

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In one way it is similar to air in the system, Frankie - which seems improbable, unless the pump delivers air…

In principle, the pump delivers a steady flow of fluid through the system, at minimal pressure (around 40 psi) with no steering input. As the steering wheel is turned; a valve in the housing assembly directs fluid into the appropriate side of the rack. This reduces return flow - and the fluid pressure increases.

The pressure increase is proportional to the force employed to turn the steering wheel against the resistance of the road wheels. This is effected by a torsion bar in the housing assembly between steering column and the pinion - twisting under load to vary pressure with the angle of deflection…

Air in the system is usually noisy, and is supposedly ejected after first fill by a couple of lock to lock turns of the steering wheel. But air in the system may cause symptoms as described, and you did mention a loose air transfer pipe - which then indeed may have some bearing…

At the rack; the air transfer pipe union adapter has a ‘bonded sealed washer’ - but I’m not sure whether a tightening of the union or some other action is required. However, a loose joint implies that air may enter the system a this point - and some blockage of the transfer line may prevent the proper venting of the system…

In theory, the pump may deliver ‘pulsed’ pressure - like a broke vane in the pump or a slipping belt. Having verified that the latter is not the case, and that correct fluid is filled to spec - one is sort of running out of options of rack problems. However was the procedure for installation of the pump belt tensioner followed…?

Others have mentioned the rack damper which is fitted on some versions. It serves two purposes; to reduce road wheel feedback by friction - and to adjust the mesh of the pinion and the rack. Excess clearance, caused by wear or whatever, is easily noticed by play in the steering wheel with the engine not running. Too tight will lead to binding at some points between lock to lock turning, engine off and the road wheels off ground…

However, this will not lead to vibration at any time. And while a malfunction in the housing assembly valve may cause it to ‘flop around’, causing vibration as described - it is a bit far fetched…

There is no doubt that you have fault - only the best remedial actions to take…

Frank
xj6 85 Sov Europe (UK/NZ)
**

15

Thanks for you time and expertise Frank.

I had another go at trouble shooting the problem today - last time before removal and dismantling!

With the front off the ground and engine off, the S/W turns perfectly with no hint of hesitation or sticking. With the front off the ground and engine running, there is very slight sticking on RH down; as the jack is lowered and more of the front rests on the ground (and the steering needs to apply more effort), there is increasing hesitation/sticking on both RH and LH turns.

I attach (I hope) a photo of where the air transfer pipe slots into the end of the rack - you can see the paint worn away where the pipe is loose and can move both rotationally and from side to side. I also attach copies of the parts book - I have type “A” (later). I applied dollops of grease where the loose pipe ends fit to effect a seal against possible air entry, but no change. No bubbles are visible in the reservoir to indicate air in the system.

If I can find someone local with a hydraulic pressure gauge I will get the pump pressure checked out - otherwise it looks like a dismantle job in over the winter.

Frankie

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16

your welcome. I get my racks from buyautoparts.com I’ve replaced the rack in my XJS and the XJ6 Series III. The price is hard to complain about too.

17

That pipe referred to is simply a vent tube to allow air to travel from one boot to the other when turning. It is not an exact seal and there is no fluid in that area of the rack unless it is leaking internally.

18

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Increased effort with be quite normal as more weight is put on the front wheels, Frankie. It’s the twist of the torsion bar in the housing that regulates pressure for power assist - and the twist increases with road wheel resistance…

Without front wheel resistance, the steering wheel is directly turning the pinion - moving the rack. Seemingly there is nothing mechanically wrong with the rack - so the problem seems exclusively hydraulic.

As said before; air in the system would explain the hesitation/sticking response to steering wheel input. The only contraindication is lack of any noise - air in a hydraulic system tends to make unusual sounds. Basically the fluid flow is smooth and silent.

A pressure test may reveal something; if the pressure is steady, the jerking may have a different cause than jerking in step with pressure variations. But likely the pressure test will not reveal anything significant…

I’m still suspicious of your air transfer pipe, but don’t know how lack of sealing would affect rack behaviour. Another thing is the ‘flow control valve’ in the pump - this is meant to open at 1200 psi to recirculate fluid inside the pump to limit the system pressure. It may malfunction, but should then just limit the pressures available - not ‘oscillate’…?

I’m not sure it’s a good idea to dismantle the rack yourself. You could contact a rack rebuilder who, from symptoms description, may have some clue…?

Belatedly, I haven’t asked when you noticed these symptoms…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)
**

1 Like
19

I come in a bit late. I’d not give up on the “air” theorem quite yet.

Yes, it is usually bled easily. both wheels up and a lock to lock turn with the engine running.

Another way is to go to an opens pace ad drie a series of figure 8’s. Fun as well!!!

Mine groaned the other day. Ooops, fluid low !!
Added some handy ATF. All well, almost. I suspect a small leak at the return hose to the reservoir joint.

Carl

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