power steering self centring

[AlanCoombs]

I've recently finished restoring a 1965 S-type. I've completely rebuilt front and rear suspension, engine, gearbox, and stripped the entire body and chassis back to bare metal.

The only thing that's not original is the steering - I've fitted the Marles Varamatic type power steering from a Daimler 420 in place of the original manual steering. This gives surprisingly light, accurate steering without resorting to a more modern setup.

However, the problem I have is that the steering shows no inclination whatsoever to self-centre. The mechanism is free and smooth, and I've checked that the castor angle is about right at +0.5 degrees (The Manual suggests 0 degrees +- 0.5 degree).

So I'm wondering if it's supposed to self-centre at all! If it is, I don't understand how it's supposed to work with 0 degrees o castor angle. It was three years ago since I drove it last, and I don't recall if it ever did self-centre then (There was so much play in the linkages then anyway it'd have been hard to tell!). I've even tried moving a few extra shims over to increase the castor angle further, which seems to have almost no effect until I run out of shims!

So I'm rather hoping somebody will just say "don't be silly, it's never supposed to self-centre". Please help! It's not unpleasant to drive as it is - it just takes a bit of getting used to.

[PeteB]

Alan,
a lack of self-centering is typical of these power steering set-ups. I usually add another degree or so of castor angle to help introduce some.

[AlanCoombs]

Thanks - that's what I thought. I've run out of shims to move over to further increase the castor, but I might try moving the aluminium spacer to the other side of the ball joint too to see if it makes any difference!

[piman]

Hello Alan,

I have had little experience of power steering, (can't stand it personally) but I do know that it is even more important to ensure the rack or box is centralised when the steering tracking is done. At worst you will have a constant pull with power steering if it has not.
It would seem odd to me that you need to deviate from the manufacturers geometry to get a satisfactory response to the steering?

Alec

[PeteB]

The figure quoted by Jaguar isn't much at all by modern standards. The tyres you use could make a difference - modern tyres have less sidewall elasticity, so theres less encouragement for the steering to straighten when cornering.

[piman]

Hello Alan\Peter,

I don't have my manual to hand, but is the MK 2 geometry different? I can't see any reason why it should be but mine certainly self centres quite readily.
It is not power assisted so I don't know if the geometry is different in that case?
Regarding tyres, these cars very often were fitted with cross ply tyres when new with little side wall elasticity?

Alec

[PeteB]

I don't think the geometry is supposed to vary between power & manual steering cars, but poor self-centering seems to be common with PAS. My comment reflects my own experience - adding a bit more castor helps, but I'd recommend checking the other angles (camber & tracking) as well as the condition of suspension balljoints & bushes before making any changes.

[Tud0]

Hello Alan/Peter,
I have a 1966 S-Type which has had the steering joints replaced and also have no self centering action. I thought that I may have done something wrong but the car has the original shims and settings so I suspect that these cars were like this from new. I also had the steering box re-sealed to cure a leak, by a fitter who worked for the original supplying company and it still leaked!He says that no one will rebuild the box and they will not fully strip it down because of problems experienced when doing so, apparently it can seize up after the work has been done!Does anyone know of a company who are willing and capable of doing this? and what is the cost. I am currently running a replacement spare box which works well but also leaks.

[AlanCoombs]

Actually, since february, the self-centering has gradually improved as I have used the car, and is really quite good now - I think it must have just taken a thousand miles or so for all the new joints I put in to loosen up a little.
I too have had problems with the steering box leaking fluid - I don't think that there can be very many owners who don't. I've removed, stripped down and rebuilt the steering box with new seals twice since February now, to fix leaks in different places, but it still leaks (From yet another, different place)! I think I've now got the leak down to an acceptable level, so I'll just put up with it. I haven't had it seize up completely yet, but I (Or my next of kin!) will let you know if it does
However, after driving it down to the Goodwood Revival last weekend, the clutch has started slipping to the point where it nearly didn't make it home - I think this is due to a different oil leak, but I can't be sure - I'm going to have to remove the engine to find out, and I'm tempted to have yet another go at fixing the power steering leak whilst it's out and the steering box is easy to get at.

[david.b]

sorry chaps ive just found this post after 2 years. There is a power steering reconditioners in Norman road Greenwich London se10 who recently stripped(including removing from car and refitting) and re tefloned my MV all in a day and for appx £300 no problems since.When i go past next i will post there telephone number