Hi,

After a fruitless wait for the pinion seal in my power steering rack to mend
itself on my 78 Scimitar se6a I have eventually got round to doing it. The
rack is off after a struggle and things that immediately stand out is they
bottom universal on the column is near seized. Removing the power valve
assembly cover reveals the pinion shaft is a little rough where it goes
through the seal and there is some, what I can only describe as 'little
black slugs' hiding alongside an 'O' ring at the base of the power valve,
all cleaned out now. There seems to be only the slightest side movement on
the pinion and removing one of the shims that lie between the rack and this
cover seems to tighten up the rotation of the pinion but I cannot yet tell
if that very slight side play will go away.
Questions.. Did the stiff UJ on the lower column strain the seal too much,
maybe letting in some grit that has scored the pinion where the seal seals.
I didn't particularly feel any three penny bit effect.
Plan of attack is, repair / replace the stiff UJ, clean up the pinion shaft,
replace the seal on the end of the power valve housing and maybe even that O
ring as I can get to it easily. Put it all back together for many trouble
free years motoring.
Does anyone have any experience of this problem that they might like to
share especially with respect to the shims - Do I remove one, the rack seems
pretty tight anyway, are they not for pinion side play.
Can I remove the pinion assembly completely and replace the ball bearing in
there - is that a worthwhile game, it seems fine anyway. Does the pinion
have to go back in the way it came out as I am unsure that I can do that,
the end is grooved not slotted where the UJ fits so it appears to fit in
anyway round, or am I wrong.

Many thanks for any help

Chris
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Hi,
I would have thought age is the factor on the seal. The motto 'leave good,
stop good' may help with this one.
A tight u/j is unlikely to be the casue of the seal going.
regards

      Steve J
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>Questions.. Did the stiff UJ on the lower column strain the seal too
>much,

Only if it has worn the bearing, which in turn would cause the shaft
to put undue pressure and wear on it.

A new seal should take care of any slight wear on the shaft.

>share especially with respect to the shims - Do I remove one, the
>rack seems
>pretty tight anyway, are they not for pinion side play.

They are normally for supporting the rack. Under pressure, the pinion
has a tendency to drive the rack away from the pinion. The shims are
there to adjust the pressure pad behind the rack teeth to maintain the
correct clearance between them. It shouldn't put any pressure on the
rack.
Over time the pad does wear and might need adjusting by reshimming.
Adjusted correctly the pad should just touch the rack.
The shims should not be used for adjusting the mesh of the rack and
pinion, although with a worn steering box, you can get away with doing
this up to a point.

>Can I remove the pinion assembly completely and replace the ball
>bearing in
>there - is that a worthwhile game, it seems fine anyway.

If the bearing is OK, my advice is not to strip the pinion assembly.
This 'box' contains the valves and torque coupling, which are
carefully set up during manufacture.
At present new ones are individually calibrated and certificated,
which gives an idea of how important they are regarding safety.

>Does the pinion
>have to go back in the way it came out as I am unsure that I can do
>that,
>the end is grooved not slotted where the UJ fits so it appears to fit
>in
>anyway round, or am I wrong.

The pinion can be fitted in any position. The best way to fit it is to
set the rack in the central position, and then fit the pinion so that
the least worn teeth on it engage the rack. This will give the least
amount of steering play in the straight ahead position. If you do
decide to adjust the play by reducing the shims, make sure that the
rack is still free, especially at the extremes of travel.
Mike.
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Thanks loads for the advice - Just what I wanted to hear and confirmed lots
of my plans. Has also scared me off sufficiently to leave me just the easy
bit to do, so I am happy with that. The only confusing bit is about the
shims - quote,

> They are normally for supporting the rack. Under pressure, the pinion
> has a tendency to drive the rack away from the pinion. The shims are
> there to adjust the pressure pad behind the rack teeth to maintain the
> correct clearance between them. It shouldn't put any pressure on the
> rack.
> Over time the pad does wear and might need adjusting by reshimming.
> Adjusted correctly the pad should just touch the rack.
> The shims should not be used for adjusting the mesh of the rack and
> pinion, although with a worn steering box, you can get away with doing
> this up to a point.

I think the shims you are talking about are on the plate on the rack housing
12 on http://www.g7lwk.ic24.net/pic0001.jpg  - I have not removed this
(frightened) but the housing that 23 &24 are in has shims between it and the
main body of the rack - these are the ones I am referring to. I should  have
made that  clearer.

No real matter though, I see what you are getting at and I shall probably
not adjust either part of the setup anyway as, like I say, the tack is quite
tight enough - it takes a lot of 'by hand' turning on the pinion but I can
turn it.
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I'm not familiar with that box, but I would say that those particular
ones are for adjusting the endfloat of the pinion shaft. If I am
right, adjust the shims to allow the pinion to turn freely with no
endfloat.

The other shimmed plate, 12  is quite safe to take off. If you can
remove any shims, so that bolting it back the rack is still free to
move, do so. As I said in my earlier post, the pad is supposed to
touch the rack without putting pressure on it.
If it has worn, now is the time to readjust it.

>
>No real matter though, I see what you are getting at and I shall
probably
>not adjust either part of the setup anyway as, like I say, the tack
is quite
>tight enough - it takes a lot of 'by hand' turning on the pinion but
I can
>turn it.

The only tightness you should feel, is the tightness of the piston
seal in the rack cylinder itself. If it is tight for any other reason
it should be sorted.
Mike.
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Chris

The rack is Rover SD1 so if you can find a manual you will find info. on
settings. The pinion should have no end float (axial / up/down movement) and
the shims are removed or inserted to achieve this. Note that the shims
adjust the pinion bearings only, not movement within the rotary valve.

The pinion shaft is in cup & cone ball races top and bottom so there would
be two bearings to replace. Having got as far as you have I'd be tempted to
remove the upper bearing only for examination. If it's OK the bottom one is
likely to be OK too.

If you remove the pinion it does not have to go back in the same mesh with
the rack teeth.

Within the hydraulic valve assembly is a torsion rod. This twists by an
amount determined by steering effort and the rotary hydraulic valve then
directs fluid to the appropriate side of the rack piston to provide
assistance. As this assistance reduces steering effort the torsion rod
allows the valve reduce the hydraulic pressure at the rack piston until you
move the steering wheel again.

The tube that connects each end of the rack merely allows lubricating oil to
transfer from one end to the other as the rack moves. It has no connection
with the hydraulic circuit.

When I rebuilt my rack Graham Walker had all the spares required.

Tony
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Fred

If you do need to replace all the seals I can offer a couple of tips.

The rack is easily dismantled but you need to warm the alloy ends so they
can be unscrewed from the tube. Heat is needed not because they are corroded
but because a sealant is used on the threads and heat softens it. Once it is
soft the ends unscrew easily. Take great care not to grip the tube too
tightly - any deformation ruins the rack. The tube is the hydraulic ram
cylinder.

A Rover SD1 manual shows the rack in reasonable detail. Once in there look
very carefully at the piston. It comprises a disc with a seal on it's
periphery. It's held in the centre of the rack bar by two circlips, one
either side. Ensure these and the grooves they seat in are in very good
condition - the circlips transmit all the hydraulic effort used to assist
the steering.

Regards

Tony

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