The curse has struck again

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white exec
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Re: The curse has struck again

Post by white exec »

I'll take a look tomorrow at possible optimal O-ring sizes for the LP and HP pipes, now all the dimensions are there. Bit late here now for such brainwork!

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Sloppysod
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Re: The curse has struck again

Post by Sloppysod »

Hi Kenny, two points.
1 - Try these people for seals if there are still working - Simply Bearings - see photo.
2 - Also I bought my rack from this Guy "http://www.kellybraysteering.co.uk/", he knows about racks, he had one left that he had no intention of selling becuase he couldn't give them a long garruntee, mine has been dry since fitted in December 2017.
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Cover of my order.
Cover of my order.

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KennyW
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Re: The curse has struck again

Post by KennyW »

Thanks Stu,

All ready ordered and on route from them. Thanks for the tip re rack.

Kenny

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white exec
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Re: The curse has struck again

Post by white exec »

Hi Kenny,

Sorry for lateness, but just had a chance to look at optimal O-ring sizes.

There are many examples of where Citroen/PSA are somewhat mean on O-ring dimensions, and achieve a leakproof seal (in the factory) with a brand new O-ring, which is minimally compressed. The compression sometimes only operates in one direction, and leaves the ring not actually decently filling the groove.

PSA are quite fond of 2mm thickness O-rings, and use them all over the place. One example of these being a tad leaky is on the screw-in plug on spheres, where the ring is quite a loose fit in the plug groove, and hardly compresses at all.

Have found that it is only necessary to go very slightly up in O-ring thickness to achieve decent compression, and a much better seal. The groove is filled better, and the ring is less prone simply to go 'flat'. A small fraction of a mm increase is all that is needed.

Using Robin's dimensions above for LP and HP pipe and bore, I calculate as follows:

HP pipe, 10.95mm ø
Groove height = 2.78mm
Groove ø = 8.30mm
Available slot for O-ring (groove height × groove depth+bore_clearance) = 3.9754mm²
An O-ring of 2.25mm thickness would fill this space.
Choice from Polymax* range would be 8mm I.D. × 2.2mm thickness

LP pipe, 11.95mm ø
Groove height = 2.45mm
Groove ø = 9.45mm
Available slot for O-ring (groove height × groove depth+bore_clearance) = 3.32mm²
An O-ring of 2.05mm thickness would fill this space.
Choice from Polymax* range would be 9.02mm I.D. × 2.2mm thickness

* https://www.polymax.co.uk/o-rings/rubber-viton-oring/
Viton/FKM quality (mineral oil proof), ShA 70/75.
Used extensively for Citroen hydraulic repairs.
Have used Simply Bearings as well; helpful for very small quantities.

More than happy for my maths to be checked!

As before, the increase in O-ring thickness is only small (0.2mm above the standard 2mm), but creates a much snugger fit. Important to lubricate the ring (eg silicone grease or Vaseline) when fitting, to avoid scuffing.

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ksanturion10
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Re: The curse has struck again

Post by ksanturion10 »

Sloppysod wrote:
30 Apr 2020, 16:15
:offtopic: Think to start selling bearings and o-rings, mech engineering seems to be a dead cause around here :-D

By the way, the dimensions are not the optimal ones, but probably will do. Just fyi, the lower limit for standard FKM (Viton) o-rings is at -15 deg C, so it should be the special compound for -35 deg C, for which I don't know the exact name, but if I was you, would probably buy what is out there for sale :)

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white exec
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Re: The curse has struck again

Post by white exec »

Not quite sure what you are recommending there, ksanturion ↑

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KennyW
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Re: The curse has struck again

Post by KennyW »

Thanks Chris,

I've been thinking the same, but I have an alternative idea worth somebody testing out who has the necessary equipment to test.

Firstly, the following question will decide if my idea is worth doing or considering.

Are the top half of the pinion housings the same dimensions between later mk 2 Xantias and C5 x7 ?

If so can they be swapped and the screw type fitting be used to secure the pipes of the C5, obviously with some modifications.

Would this change affect the operation of the power steering ie narrower pipe ID causing increased pressure thus blow top seal on the pinion.

Just an idea thrown out for comments and thoughts

Kenny

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KennyW
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Re: The curse has struck again

Post by KennyW »

Well started to remove the necessary bolts etc to drop sub-frame to remove rack.

An observation the rack appeared to be dry which suggests to be the leak is from a low pressure area, will find out how my mod has been performing.

Tempted to had some additional seals on the tube below the o ring grove to fill the gap, ie small seals stretched over the pipe.

Will keep everybody updated.

Kenny

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white exec
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Re: The curse has struck again

Post by white exec »

Additional seals/rings below the main ones would have to be extremely thin, as the gap (on both pipes) is only 0.105mm, from the figures above.
An additional O-ring in a proper groove might make sense, though, but not easy to produce a decently smooth groove.

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Paul-R
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Re: The curse has struck again

Post by Paul-R »

white exec wrote:
04 May 2020, 22:17
An additional O-ring in a proper groove might make sense, though, but not easy to produce a decently smooth groove.
Basically what I suggested in another thread about this problem.

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white exec
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Re: The curse has struck again

Post by white exec »

It could be easily done on a lathe, if it were possible to get the pipe(s) accurately mounted in the chuck. #-o

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Paul-R
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Re: The curse has struck again

Post by Paul-R »

Paul-R wrote:
04 May 2020, 22:22
white exec wrote:
04 May 2020, 22:17
An additional O-ring in a proper groove might make sense, though, but not easy to produce a decently smooth groove.
Basically what I suggested in another thread about this problem.
Found it!
viewtopic.php?p=641788#p641788

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KennyW
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Re: The curse has struck again

Post by KennyW »

Well rack off and it appears it is not leaking from the top pinion seal.

The pipes seemed well sealed and needed a little assistance to come off.

But there was a mixture of water and oil in both track rod boots a lovely off green colour ( definitely NOT LHM fluid) as I know I filled the rack with orange LDS fluid.

Could the seals at both ends showing signs of wear due to the ingress of water. I changed the boots just before the MOT in Jan 2020.

Thoughts please everyone.

Kenny

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KennyW
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Re: The curse has struck again

Post by KennyW »

Well collected another rack today from Glasgow Power steering, speaking to one of the mechanics he said they strip down the rack fit all new seals and have the pinion shaft turned down until clean then fit an oversized seal to finish the job.

I have made slightly different mod by removing the small metal bracket attached to the top of the pinion to create a good securing location for a ball joint dust cap.
Here are some photos,
Attachments
IMG_1079.JPG
IMG_1077.JPG
IMG_1076.JPG
IMG_1075.JPG
IMG_1074.JPG

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KennyW
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Re: The curse has struck again

Post by KennyW »

Sorry,the photos are the wrong order and I need to find an original.
C5_X7 lump 6.jpg
C5_X7 lump 6.jpg (32.17 KiB) Viewed 73 times
Thanks to Chris for borrowing your photos that's the bit I cut off
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C5_X7 lump 3p.jpg
C5_X7 lump 3p.jpg (37.07 KiB) Viewed 73 times