Fixing The Straight Ahead "dead Spot" Vagueness On Pas Racks -

[Anthony 1,002]

PAS steering racks seem to commonly suffer with varying degrees of "dead spot" vagueness around straight ahead, which generally speaking, non-PAS racks don't.

 

The question is - what is the cause of this and, perhaps more importantly, is this in any way (easily) addressable? I sure that I've seen someone (Rippthrough I think?) mention that it is sortable, but couldn't find the post where he mentioned this and I don't remember him mentioning any detail.

 

I've been spoilt of late as the PAS racks I have on both of my cars are really precise and don't suffer any noticeable vagueness, but I've been reminded of it by a couple of PAS GTi's I've driven recently that were awful and really spoilt the feel of the car and this got me thinking about whether it can be solved. The steering rack from one of these is sat in my garage currently, effectively scrap in my eyes as I would never consider using it on my own car or selling it to anybody.

 

I'm happy to accept that it may be an issue of wear and that the vague racks are only fit for the bin, but it seems odd that only the PAS racks seem to be like this and that there's no other obvious wear symptoms - no slop, no play, no vagueness once away from straight ahead, no uneven weighting, no movement in the N/S bush etc.

 

I know that I've seen two types of PAS lower column, one that is solid (that GTi's should all have) and one which has a rubber insert (which I believe some base models have, and aftermarket replacements usually are), and I'm sure that the later type wouldn't help matters as you'll need to overcome the "give" in the rubber before steering inputs result in the rack itself turning, giving vagueness as you initially come away from straight ahead.

 

I also know that there's different PAS racks from the factory depending on model, which given that they're all the same fitment, suggests that there's something different internally - could the "vague" racks be non-GTi ones for example, and if so, what's different?

 

The only clue I can see is that on Servicebox the non-PAS racks have different piston and spring/shim arrangement that sit behind the diamond shaped plate underneath the pinion for injection (ie GTi) and non-injection models, although the PAS ones are listed as all being the same so it might be a red herring, or might suggest that the fix lays with those piston/spring/shims (perhaps needing more preload or something)?

 

Thursdays idle ponderings...

[Gman 29]

"I've been spoilt of late as the PAS racks I have on both of my cars are really precise and don't suffer any noticeable vagueness, but I've been reminded of it by a couple of PAS GTi's I've driven recently that were awful and really spoilt the feel of the car"

 

ha ha, you were much politer to my face about my crappy rack!

 

It would be good if someone can provide some insight on this. However, is it simply limited to 205 power racks, or has anyone ever experienced similar symptoms with a Xsara VTS rack?

 

Graham

[Anthony 1,002]

Yours wasn't the worst one, but yes, it's certainly far from brilliant and did detract from the feel considerably - I didn't realise how much until I got back into the GTi that I'd driven over in which, despite it's bus-like 3.9 turn non-PAS rack, felt wonderfully sharp and agile by comparison

[Henry Yorke 269 3 Cars]

Does the vagueness still exist in the racks if the PAS is disconnected? If so then perhaps it is a pressure related issue and possibly due to some seals deteriorating?

 

Just pontificating your ponderings!

[DamirGTI 342]

Only thing i've seen in OE PSA "news flashes" documents for 205 concerning steering was problems with the lower column cam bolt issues :

 

Diagnosis - lower section of the steering column badly located the steering rack pinion .

 

Remedy - the cam bolt and lock nut must be replaced and tightened to the 2.25 mdaN .

 

But this could be felt on a steering wheel at standing still or parking .

 

For PAS rack , i found something with regards to the XM PAS rack issues , apparently they've had issues with the steering ram mounting bushes .. so new strengthened bushes where made and replaced within the warranty , also the tightening torque of the steering ram fixings has been increased to the 9 mdaN and with 10.9 class bolts replacement .

 

D

Edited February 28, 2013 by DamirGTI

[S@m 156]

For PAS rack , i found something with regards to the XM PAS rack issues , apparently they've had issues with the steering ram mounting bushes .. so new strengthened bushes where made and replaced within the warranty , also the tightening torque of the steering ram fixings has been increased to the 9 mdaN and with 10.9 class bolts replacement .

 

D

 

Aswell as the XM that issue affected the C15 which, as we know, has 205 running gear at the front. This could be a red herring but here's a quote

 

Vehicle application : C15 Diesel Power-assisted steering model.

Applicable from RPO number : 7189.

1. Description

Power-assisted steering is equipped with a new "no play" rack bearing (opposite side to the steering pinion).

The

only difference from the old rack bearing is the type of material used

(plastic and rubber instead of teflon-coated sintered steel).

N.B. : A "no play" rack bearing is already fitted in the case of manual steering."

What makes it seem apt is that manual racks already have the 'uprated' part. It could be completely unrelated but what Damir said reminded me of that.

[B1ack_Mi16 67]

Well. One thing I noticed on my PAS rack that I got from a 205 diesel was that the lower steering column part (the one going through the bulkhead) has vulcanized rubber in it, and steel-to-steel contact after a slight amount of rotation (possibly to be able to still steer the car if the rubber disintegrates).

 

But maybe it's the rubber in the lower column part that makes them feel vague, as I believe the stiffness of that can't be well defined before it's under a certain amount of load.

 

I'm not sure if they all (PAS rack lower columns) got rubber in them, but mine certainly does and it must make a difference for sure.

[Anthony 1,002]

There's two types of lower column - one has the rubber like you mention, and the other is solid (ie no rubber) which should be the type on GTi's

 

The rubber ones are certainly worse, no question of that, but I feel that there's something with the rack itself as well.

[welshpug 1,655]

I remember Phillip saying something about this but dont know any further details about the cause or remedy.

[Rippthrough 98]

It's play in the shuttle valve system, it's needed for the torsion bar in there to give feedback to open the hydraulic valving in the shuttle. The reason you don't feel it with PAS is because as soon as you flex the torsion bar the hydraulics come into play so it doesn't feel as vague.

 

You need to open the shuttle valve area up, put some shim steel down either side of the slot to take the slack out, and preferably, TIG weld it in.
If you make the steel a good fit you can probably just epoxy or loctite it in there, but I've not tried that.

 

The other option is to take the torsion bar out and put a big piece of tube in it's place and weld it either end. Both will work.

Edited March 3, 2013 by Rippthrough

[Rippthrough 98]

Gotta take a rack apart for the buggy next week so I'll get some pictures

[Anthony 1,002]

Interesting info - I'd certainly be interested to see the pictures, as I've not stripped a rack to the extent that you can access the hydraulic valving

[Rippthrough 98]

You can change the amount of assistance/feel on PAS racks with the torsion bars in there too, some of the 405/BX versions have different diameter bars.

[Henry Yorke 269 3 Cars]

You can change the amount of assistance/feel on PAS racks with the torsion bars in there too, some of the 405/BX versions have different diameter bars.

 

You'll have set the masses off now with statements like that Phil! I foresee ultimate Xsara VTS racks being built with BX torsion bars etc in them!

[Rippthrough 98]

It'll keep 'em happy trying to find which bars are which I'm sure