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Inside the Suspension Pump - some photos and thoughts

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robingc33   
Tue Nov 15 2016, 08:42pm
Joined: Aug 25 2015
Member No: #2303
Location: NW Essex
Having had to bite the bullet and replace my suspension pump recently I thought I'd satisfy my curiosity by taking the old one apart and in the process maybe find what was wrong with it (that made it give up, smoke and blow 60A Maxifuses!). I've also taken a few pics (below as follows) which might be of interest/use to others.

1) The bottom view of the complete pump assembly...

2) After removing the end cover plate from the electric motor (three screws) the end of the commutator and brushes are exposed...

3) The brush assembly can now be prised out leaving the motor commutator exposed...

4) If the four Torx screws are removed from underneath the pump block, the plastic case containing the suspension ECU and pump valve controls can be separated - now revealing the four electro valves - and the mating solenoid coils within the plastic ECU assembly.

5) The electrovalve mechanics themselves are a push fit into the metal pump body, each retained by the three-holed plate and two Torx screws. The valves can be dissasembled and comprise the valve seat body, a very fine, pin-like pointed valve slider, and a small spring and spacer rod within the round-topped, exposed part of the valve assembly.

I must admit as an ancient LHM-er I was expecting mechanical valves in the pump not electro-valves - such is progress, etc. and since I couldn't see any obvious damage to the pump motor and it all rotated OK by hand, it makes me wonder if my fault was due to the failure of an electrovalve - making the pump work effectively against a hydraulic lock???
I haven't tried applying 12V to the motor yet - but it will be interesting to try it!

Anyhow - maybe some of these pump failures are more complicated than thought and could be the result of valve/ECU failure?

Robin



















gmerry   
Wed Nov 16 2016, 08:51am
Joined: Dec 11 2009
Member No: #21
Location: Scotland
Great post. Any sign of a micro-filter inside the valve block?

I think we posted on this years ago, but with a combined power steering / hydraulic suspension system, there is the possibility of wear debris from the steering circulating through the suspension valves?

If you uncouple the motor from the pump, does the motor run OK?

regards
onthecut   
Wed Nov 16 2016, 08:52am
Joined: Sep 20 2016
Member No: #2793
Location: West Mids
Hi Robin.

We have a C5 X7 which I'm guessing will have the same set up. On that, it will go for weeks without issue, but then pop the fuse. This happens most noticeably if the car has been fully raised or lowered a couple of times, say at service or MOT time. Also, it is evident the pump runs for a considerably longer period than might be expected, say following a door opening.

To obviate getting stuck, we moved the fuse outside the box to a more readily accessible spot. Other symptom we have is that sometimes after jacking or lowering the car, it will expel fluid from the reservoir, even though it is not over full.

Did you have any of these symptoms ? Looking at your motor it doesn't seem likely that is at issue -- they look a very healthy set of brushes.

Mike.
cruiserphil   
Wed Nov 16 2016, 11:07am

Joined: Jan 24 2010
Member No: #38
Location: Celbridge
Thanks for that Robin,

As Mike says, lots of life in those brushes. What do you think - is it something that would benefit from removal for a strip down and clean up at some stage of its life?

Best regards,

Phil C.
robingc33   
Thu Nov 17 2016, 06:12pm
Joined: Aug 25 2015
Member No: #2303
Location: NW Essex
Thanks for your interest and comments.

In reply to your questions...

G - Yes, there appears to be a little circular gauze filter in the (bottom/open) end of each valve assembly - I've attached a (poor!) close-up pic below, but it gives the general idea. I guess one could separate the ECU, then remove the valve assembly and reverse-flush it through if needed/beneficial.

When I first examined the pump, the motor wouldn't turn more than a few degrees in either direction but... I realised there was still some residual fluid inside the pump since the garage had carefully plugged the in/out pipes with the temporary plastic transit plugs from the new assembly after removing it and, since the pump wasn't powered (so all valves shut by default) there was a hydraulic lock within the pump. Once I'd drained the residual fluid, the motor and pump could easily be turned by hand.

So today I had a go at powering the motor.
The motor has three connections, two big traditional blade-type connectors in one shell and a single pin in another (both shells are adjacent on the outside of the plastic package that wires onto the brushes - on the front when in the car).
Guessing the two big connections are for power I connected them to a spare battery - it's easy to guess which pin is which since the red and black brush wires come out of the package to go to the brushes close to each end of the two pin connector. But nothing happened. So I measured both brushes and found +12V on both - no suprise then!
So I assumed the third single pin must turn the motor on and off (so effectively this plastic package is a relay unit). This single pin measured 0V with nothing connected, so I guess it needed 12V applying to energise the motor.
Sure enough, on applying 12V to this single pin the motor started up!

However - the cables I was using (mains lighting cable - so only 6A rated) started to get pretty hot, the motor started to slow and smoke appeared from inside the motor!

On removing the motor end cover again I found the smoke appeared to come from around one of the wound coils fitted on the brush assembly plastic plate - there are two of these coils (pic below - bottom one smoked).

Looking at this assembly the smoking coil looks pretty messy compared to the other non-smoking coil. The smoking coil felt very hot, whereas the other was only luke warm.

My pump died whilst I was faffing about intending to replace the reservoir outlet pipe clip. I foolishly changed the height to "low" whilst it was sitting at "normal" height with a jack under the OS Front jacking point; there was a significant fluid overflow from the tank as I did it and the pump stopped working thereafter

So - I'm starting to wonder if some fluid got into the motor somehow (there are some small breather holes in the case - or maybe it breached the pump/motor seal somehow?) - and looking at the brush assembly when the image is rotated to match it's orientation in the car (pic below), the smoking coil is at the bottom - and that lower area of the assembly does look a bit suspect oily-wise - so maybe oil got inside??

But my pump would not operate at all after my "trauma" and just blew fuses and smoked.

If an electrovalve failed it could block the pump rotation, but my chances of checking them in operation now to verify that are a bit slim cause it's all ECU driven.

My car has only done 57k miles and has effectively had mini fluid-changes quite recently due with strut replacement and replacement of leaking reservoir tank pipes, so the fluid was pretty clean.

Or maybe this coil is faulty?

So I'm still not 100% sure what happened!

Anyhow - hopefully the info is useful to others.

Robin







Frode   
Sat Feb 17 2018, 09:07pm
Joined: Jun 08 2017
Member No: #3171
Location: Bergen
Hi!

I have recently gotten some of the issues discussed in this thread. It started with a substantial leak from the front right corner, below the third front suspension sphere. It stopped by itself. The Citroën dealership did not find a leak, even after leaving the car in high position for two days. After I returned home, there was - no surprise - again a large leak. I could see drops eminating from one of two small holes above the third sphere. These holes are situated directly below the pump.

It dawned on me that both leaks happened after I had reduced the hight of the car (as with Mike, above). Since pressure is then building up in the tank, I thought a small fracture in the tank could be the culprit, but could not find any sign of LDS on the lower part of the tank (investigated with an endoscope inspection camera). I have however not yet tilted the tank to look properly below it - is this possible without emptying the tank of LDS?

If there is indeed no fracture in the tank, I am wondering whether it could be a seal on the suction side of the pump that is failing. Normally, there is low pressure here, but when the suspension is lowered, pressure is much higher, I guess. I am also worried that a failing seal may admit LDS into the electrics, as might have been the case in Robin's pump. My pump is working fine for now, but I would like to try to save the pump if there is a chance it may fare as above.

Does any of this sound reasonable? Is there such a seal (where?), and would it also admit LDS into the electrics if it failed completely?

Thankful for any thoughts and help on this potentially very expensive topic.

Best,
Frode
Bergen, Norway
Frode   
Sun Feb 18 2018, 09:51am
Joined: Jun 08 2017
Member No: #3171
Location: Bergen
Short update: I tried to tilt the LDS tank without bleeding it, but it seemed to be stuck underneath. I gained a bit better view of the pump, and if I had to guess, the tank is the problem, not the pump. But it might be that this is just my hopes talking.

I topped up the LDS level (about 1 liter too low), and now I can keep taps with the level, at least.

I am of course wondering whether the Citroën dealership forgot to open the cap before lifting the car, creating the problem in the first place. And if I trust them to change the tank, will they forget to prime the pump again, possibly making matters worse? I guess the same applies to the C5, so I probably should not worry. But I do.

Best,
Frode
Dan595   
Mon Feb 19 2018, 06:17pm
Joined: Nov 26 2010
Member No: #299
Location: Wiltshire
I had to replace the suspension pump (i.e. 'BHI unit') at 198,000 miles (intermittent short circuit) and there was plenty of life left in the brushes. I don't think these pumps have a particularly high duty cycle, but they do work hard for a few seconds when needed. I had to drive 30+ miles with a failed pump and whilst the car was pretty low by the end, it wasn't right down - it's not like an LHM system where the pump runs all the time and pump failure has your mudflaps on the tarmac pretty quickly.

I do think that the pump is vulnerable to LDS leaking from the tank, specifically when the tank is overfilled (I think that this is very common) and the system is then depressurised. A collar that fits to the top of the LDS tank to contain excess fluid when depressurising would be a very useful device.
 

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