C5 X7 Steering Rack - Again!

[bobins]

I'm still having difficulty in exactly visualising the positioning of that rusted shaft, but assuming the photo above shows the rack spigot poking upwards through the footwell floor, I am guessing that the rust is due to the rack and the shaft spigot being open to road weather and spray.

The link above (viewtopic.php?f=3&t=59741&p=571475#p571494) shows a gaiter seemingly fitted on the top-side, and sloping downwards to the pair of fixing studs. This might be good at keeping cabin fluff away from the spigot, and draughts and weather from coming upwards, but would do nothing for keeping weather off the rust-prone spigot and its bearing.

Would it not be better if the gaiter (or a more suitable one) were inverted, so that its narrow (circular) end was in contact with (or better, clipped around) the rack bearing casting, and its top (bell) end fitted that floor aperture? This would keep weather off the shaft. The OE gaiter could also be fitted (on to the two studs), and the 'surrounded' spigot heavy-greased.

Yep - the photo shows the pinion shaft sticking up through the floor. The lower end of the steering column fixes on to it at that point. There is normally a large rubber boot hiding the top part of the pinion shaft - the boot serves to stop draughts, noise and crud coming up into the footwell. The shaft itself isn't really exposed to the direct spray of water from the road - no more than the back of the engine would be - but it's not really protected either, the existing boot just sits over the top of the shaft whilst the bottom of the shaft is exposed to road muck and water.
The problem is that the shaft is made of low quality metal that has near zero rust resistance. Pinion shafts don't normally rust - at least not to this ridiculous level - and most cars have their pinion shafts exposed to the elements to a certain degree and they survive OK, it's just that the C5(X7) ones seem to be made of a highly reactive steel. The trouble with fitting an inverted boot around the shaft is that it could trap and hold water. If you go through floodwaters it could fill up with crud and water and make the problem worse. There's also that annoying casting by the shaft seal that gets in the way of fitting anything like a set of bellows or a boot. I think a coating on the shaft (Grease / wax / Denso tape / etc) is the way forward.
Last year there was a bit of a kerfuffle in Japan when it was discovered that the Japanese steel manufacturers had been lying about the quality of their product, and substandard steel had been supplied to loads of companies around the world for years. I wonder if these shafts are made from some of that steel. I don't think Citroen would ever admit to there being a problem with the steering racks because that would cost them money.

[GiveMeABreak]

Yes I remember that fiasco. I haven’t (certainly not on the forum) of other users if other vehicles having any issues as yet though, unless they used other manufacturers for other models? A good point though, it has to be the quality factor here and the substandard steel used. Utterly disgraceful and akin to using a chocolate teapot.

Roll on tomorrow when the new one arrives. I’ll see if there are any identifying markings on the new rack, and fingers crossed it doesn’t say ‘Cadbury’s’.

[wurlycorner]

Any rubber boot you fix to the shaft will still not fully seal against the very bottom of the shaft and the seal in the rack - there will always be a sliver of a gap there and exposure to the air/water (there has to be, since the seal/boot will be entirely separate and must rotate). obviously it will protect the main body of the shaft well but I'm suggesting it will still leave the very point that matters (the contact area right down where it rubs against the seal) at risk?

I think I'd advise spraying the (new/clean/fully de-rusted shaft) with a good coat of galvafroid, all the the way down into the seal lip and once dry, cover in a heavy marine grease.

Also a thought on why this shaft might get more than it's fair sure of moisture build up - presumably the footwell a/c / heater outlet likely blows air over this area? Which will condense on the shaft? (just a thought)

[bobins]

The racks are made by ZF Lenksysteme, at the time the company was 50:50 owned by ZF and Bosch, but now it's wholly owned by Bosch.

Poor quality rack 1 - own work

Poor quality rack 2 - own work

Of course, we assume that these pinion shafts are failing due to duff steel used, but what if ZF used exactly the correct grade of steel that PSA specified ? The average age of a car is well under 10 years old these days, so what if PSA wanted to fit a major (and fairly expensive) component that was only designed to last the average age of a car ?
Cynical ? Me ? Only very slightly

[wurlycorner]

I doubt very much that Citroen would specify the steel to be used. I don't believe they would even have designed the rack, they would have simply given the requirements and space constraints to ZF and said 'come back with one that does that and costs no more than x and all our standard procurement t&c's'

Might be worth contacting ZF for comment on this issue. They will tell you any warranty is via Citroen of course, but might show a bit more interest in the technical issue (if nothing else than for future products).

[white exec]

Take the point about any gap at the bottom of a lower gaiter which allowed shaft rotation.
Problem with a clamped gaiter is that superfluous cast lump. Personally I'd be tempted to remove it, smooth off, and clamp, and hope the rack would never need replacing (ie exchanging), because its weak point was protected.
Guess the cheap, safe and easy protection is the tape, and a dose of heavy grease atop the bearing to stop water getting into it.

What a sh*tty bit of design/build. If problem no longer exists (eg C6), then PSA must have clocked the corrosion issue, and done something about it.

[xantia_v6]

What a sh*tty bit of design/build. If problem no longer exists (eg C6), then PSA must have clocked the corrosion issue, and done something about it.

The C6 pre-dates the C5 X7 but they (mostly) share the same platform.

[white exec]

Just taken a quick look at Parts, C6 racks. Different rack altogether by the looks of it.

[GiveMeABreak]

I'm wondering if the C6 racks were supplied by another manufacturer - who further up the supply chain sourced the steel from another supplier other than the dodgy Japanese firm with the poor grade steel?

[EDC5]

Having had another look at the rack that Elis has fitted to his C5, I'd say that that fibre type collar is an excellent solution as it covers right down to the pinion seal. It's just a pity we don't know where Elis' rack came from



viewtopic.php?f=3&t=59741&p=571475#p571494

I wish I knew too. As I said in the other thread, I had absolutely no service history with the car but the rack has definitely been replaced (and so has the BSM buy the look of the date printed on it).

I'm wondering if the C6 racks were supplied by another manufacturer - who further up the supply chain sourced the steel from another supplier other than the dodgy Japanese firm with the poor grade steel?

Also, what about the 407 and mk2 C5's ? they're all built on the same platform, so should have similar racks.

From what I gather there may be some quirk of aerodynamics (possibly caused by the under tray design) that causes road spray to get to the pinion shaft. Other cars with the same platform obviously don't have this issue, possibly because of the distance of the rack from the footwell. It's also probably due to the fact we salt our roads in winter; that won't help either!

[bobins]

Also, what about the 407 and mk2 C5's ? they're all built on the same platform, so should have similar racks.

From what I gather there may be some quirk of aerodynamics (possibly caused by the under tray design) that causes road spray to get to the pinion shaft. Other cars with the same platform obviously don't have this issue, possibly because of the distance of the rack from the footwell. It's also probably due to the fact we salt our roads in winter; that won't help either!

Here's a shot of the important bit of a 407 rack, and they seem to suffer pinion shaft rust as well, just not to the same level as the C5

407 steering rack pinion

[white exec]

Could that pinion shaft be made from stainless steel, as part of a trade-service exchange/refurb? Likely no interest in doing this, for the sake of future sales.

[bobins]

In theory the shaft could be made out of anything - providing you can match the wear characteristics and it'd match the required strength and stability in a crash test.

Having looked into the 407 racks a little more, it would seem that - in the case of the pinion shaft and its housing at least - they were made by KOYO, not ZF. There may well have been some made by ZF during the lifetime of the 407, but I've definitely found at least one made by KOYO.
ZF ----> Instarust. KOYO ---> Not so Instarust ????

[Paul-R]

So, how different to the X7 rack is the 407 rack? Could it be "persuaded" to fit?

[bobins]

I was thinking more of stripping the pinion shaft out of a 407 rack and comparing it with a C5 shaft
Although there's a good chance the complete 407 racks and C5 racks are basically the same, there is scope for quite a few variables : hydraulic pressure they run at, fluid spec / compatibility of internal seals, rack ratio (turns of steering wheel in relation to movement of rack ends), length of rack (TRE to TRE, though there is scope for altering this by adjusting the TREs), maximum 'throw' of rack from full lock to full lock.