HP Pump

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pale

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Tadpole
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Is removing the HP Pump and fitting a refurbished one on a DS21 BVH a job that can be undertaken by a very limited amateur? I can do basic services, change suspension boots, change brake pads but that's about it. I have seen a video on " servicing the goddess" and after watching am thinking I might attempt. I do not have access to a hoist but have a set of high ramps.

Thanks for any help forthcoming.
Tez
 
Tez, it is a DIY proposition but more fiddly than for the manual versions because you have the third row of the pulley to run the gearchange regulator unit above it. Manual 814-2 (you have the pdf?) gives instructions in operation DX 391-1 and access will be much easier with the RHF guard off.

Regarding this and your note here:
https://www.aussiefrogs.com/forum/index.php?threads/ds21-bvh-accumulator-sphere.152022/post-1833848

1713785488827.png


Yes, you can buy all kinds of exchange parts for your DS, but that becomes expensive very quickly. Many parts on a DS are adjustable or fairly easily repaired. There are other owners or former owners who can offer advice. You would be up for a rack sooner or later in any case and the spheres won't hold their charge beyond a few years regardless. You have covered a few of the usual DS failures already.

Perhaps, you might want to check whether there is a large return flow back to the reservoir? Did you have someone comment about this or suggest an excessive return flow when the rack was diagnosed? It may not be the pump. The reasons the pump cycles in/out rapidly will be either a flat accumulator or a large internal leak. If the pump is no developing enough pressure then it may have a longer cycle time as it doesn't reach the cut out pressure. Pumps are most commonly overhauled due to external leakage, but may not develop enough pressure if the pump body has cracked between two bodies as opposed to somewhere where it still works but leaks externally. There are a few good threads on the pump overhaul and some are listed in the Thread of Excellent Threads sticky at the top of this forum.

p.s. Just a long-shot thought about the regulator. Where did it come from? Was it set for an accumulator of around 62 Bar or could it be set up for a 40Bar accumulator. it makes a difference as the in/out pressures are different. It is unlikely to be the explanation but not impossible.
 
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Thanks David. Yes, I was assured there was excessive return flow from the rack. Recently I checked the return to the tank from the centrifugal regulator and it was 125ml/minute. I was told by an expert a couple years ago that the pump was not supplying enough volume . The pump has a small external weep. I don't want to replace the pump and still have the problem. I'm not enjoying my ownership as much as I should be because of not being able to find source of internal leak.
Thank you for your advice.
Regards Tez
 
after replacing the rack and regulator, the most likely candidate is the pump. Your cycle time should be 30m to m40s, even 20 is acceptable, more than that time to look. It maybe worth rechecking the accumulator sphere, dont assume anything with a D ! The other less likely possibility is that the brake valve could be leaking.
If its any consolation, after replacing all those items, the hydraulic system should be great for many years, with the exception of leaking boots or return hoses. Speaking of boots, have you checked the bump stops ?
 
If you look at the other thread linked back to earlier, faulksy mentioned there are checking procedures and specs in the manuals. That's worth looking into and noting that a portion of the hydraulics system can be isolated. Be careful with a BVH and be certain there is no gear engaged if you go to start it with the gearchange hydraulics isolated during a test.
If the pump is not supplying enough volume, there are three possible reasons I can think of being: 1) suction problem, maybe drawing air; 2) the pump body has a crack, and; 3) one or more of the disc valves #6 in the base of the pistons no longer seals properly and allows internal pressure leakage.

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Another common problem with pumps is stuck pistons which won't necessarily jam the pump but reduce it's output and make it noisy

The seals between pump body and the cast iron front bearing carrier can also fail but that tends to produce external leaks.
 
Just rebuilding my HP pump again.... I used a kit of seals first time around but discovered I had a slight but persistent weep via the shaft and through the bearing. Apparently this is not uncommon. My hypothesis is that the seals were not quite the right size - as i can't see any other reason why it it's started leaking when it did not do so previously. I've searched out a couple of seals of the exact Citroen size and am fitting them now.

I've inspected and 'flatted' the brass/ bronze seal carrier and the bearing to improve their surface-to-surface fit. The discs highlighted in the photo above had a very slight wear ridge to them - so i turned them over. I don't think a shaft seal weep and minor wear on those discs would be enough to significantly reduce pump pressure and cycle times, but that's an opinion borne out of ignorance on my part :)
 
Did you lap the faces of the bearing and bronze ring last time? The bearing gets a slight groove in it and perhaps fitting a new seal shifts the relative positions enough to affect the sealing? You can turn the bearing around for an unworn surface.
The surface the disc valves contact can also become pitted, so inspect them carefully and maybe rectify.
 
David S said:
Did you lap the faces of the bearing and bronze ring last time? The bearing gets a slight groove in it and perhaps fitting a new seal shifts the relative positions enough to affect the sealing? You can turn the bearing around for an unworn surface.
The surface the disc valves contact can also become pitted, so inspect them carefully and maybe rectify.
Click to expand...


Hi
No I didn't lap them last time but inspected them when I removed them this time. No obvious burrs or grooves.that might account for a leak (which is why i focused on the two shaft seals). As i'm sure you know, the bronze ring is only held against the bearing by a spring which only exerts a modest amount of face-to-face pressure so i'm not entirely sure how their is a leak free seal even when new. I had wondered whether the bearing had not gone in true when i refitted it, but don't think that's the answer as i can't see how Citroen could have guaranteed 'true' when the pumps were first assembled. Also, there is negligible scope for the bearing NOT to go in true - it's a tight press-fit.

This time I lapped bush and bearing. I found that the inner part of the bearing sticks out very slightly more on the side that faces the bronze bush - meaning it could be lapped without the outer edge also being lapped. i don't know if the bearing was designed that way, but it went in the same way it came out. I also lapped those valve discs and turned them over as they had a surface sheen on their closing surface. I also checked the alloy pump body for signs of cracking.

I won't know if this pump holds until i can get it on the car and run it under pressure.
 
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