A good clue or a simple coincidence?

alan s · Post by **alan s** » 12 Jul 2003, 04:25

I posted this elsewhere in response to a question but thought it worthy of discussing here due to several questions in recent times on this topic.
I have a CX that I'd decided (in my wisdom) to fit another pump to. With old pump in one hand & replacement in the other, I turned both by hand & both seemed on par from observing them. When I removed the old pump, I noticed that the original clip was still in place at the pump end so I chopped it off & replaced with a new jubilee clip.
I also fitted a new seal in the HP outlet.
Prior to this job, this car would "sit down" in minutes after parking & I mean that quite literally; two minutes & it would still be observed rising on start, 5 a fair bit and after 30 minutes almost completely down. Since these jobs, the car stays up for ages, pumps up 10 times quicker & the power steering still works at low speed.
The points I'm making are:
Slow pump up & heavy steering at low speed I can see being the pump & am prepared to concede that my "test" on both pumps was primitive so yes, that possibly was the cause....but.....the staying up I can't see being the pump unless the pistons were leaking so badly that the pressure was bleeding back through the pump & back to the LHM tank. A more likely scenario I feel could be that either the intake was leaking from the pump end of the hose or was leaking pressure but not liquid from the HP connection. If either of these are the culprite, then how many doseur valves & F/Ds have been changed for practice on BXs over the years??
Anybody any theories or thoughts on this theory??
Alan S

jeremy · Post by **jeremy** » 12 Jul 2003, 14:36

Alan
Your car was running on an oil/air emulsion. When the car stopped the air in the fluid fromed bubbles and the height corrector valve seals nicely for oil, relying on its surc=face tension but doesn't seal well for air.
Well that's my theory - perhaps it will kick off another fascinating discussion[:D]
Jeremy

AndersDK · Post by **AndersDK** » 12 Jul 2003, 23:03

Jeremy -
I vote for that !
Air in the LHM is a big problem and caused by 2 common problems :
1) the pump feed hose is commonly dodgy (cracked) on the pump stud - you won't see any leaks from the hose - since it's under small vaccum - from the HP pump's suction action - and the fluids own weight when trying to flow back to reservoir.
2) the filter meshes in the reservoir may have cracks - not disintegrating the normal air bubbles from returns.

jeremy · Post by **jeremy** » 13 Jul 2003, 00:51

Alan
Has the new pump affected the ride quality? I should have thought that air-laden LHM was quite compressible and could give a soft bouncy ride.
Jeremy

tomsheppard · Post by **tomsheppard** » 13 Jul 2003, 01:40

I wonder if I may have felt this phenomenon. My car has been hot recently. Today for the first time, I saw the fan run! It sinks much more quickly which is to be expected. I imagine that the air would be of such a small volume as to induce a low amplitude, high frequency bounce at about 3-5 Hz. The pump itself: gives a noise like a rattlesnake every 11 seconds at this temperature compared to 17 in ordinary British weather. Raises car fron fully down to fully up in 45 seconds after being left for a week. Fluid and filters clean in tank which was renewed 50,000 miles ago. The struts are getting past their best at 150,000 so Do I do the Hydrorincage now and then rebuild the struts or do I do the struts first?

AndersDK · Post by **AndersDK** » 13 Jul 2003, 02:18

Tom -
15 - 17 sec's clicking frequency is way too fast anyway.
We're talking BX here ?
If so - then simply test the LHM flow from the SMALL hoses at reservoir. Any flow is a NO-GO - only slow dripping is acceptable.
If you have flow - repeat test at the front struts return hoses in wheelarches. Flow here means strut ovehaul ASAP.
If you have flow - but NOT repeatable in strut returns - it may be your brake valve.
If no flow - then most probably the acc sphere is flat.

alan s · Post by **alan s** » 13 Jul 2003, 03:25

The reason I think you guys are on the right track is that this is the car that I was forced to run ATF in the system in an emergency when I bought it due to a drama out in teh bush & 1000 klms away from the nearest LHM.
ATF is thicker, yet it seemed to make no diference to the rising or dropping of the suspension. That to me, took the internal leaks out of the equation.
I've still got my money on a dodgy hose/clip.
Alan S

tomsheppard · Post by **tomsheppard** » 13 Jul 2003, 03:26

Thanks Anders but I have a suspicion that all is actually well . I have been told by many who know that I shouldn't worry about anything over ten seconds.Your roadworthiness people may be being over critical maybe? (Herhjemme har vi ikke Statens Bilinspektion!) And I bet they don't like Citroens...
Flow return pipes are a good check though; I printed off loads of stuff on it just in case it was useful and forgot I had it! I am generally against opening the system up. Nothing else gets in that way and these tolerances make watchmaking look like crude engineering. Old Andre was a damned good engineer and he must have hired some teriffic brains over the years. The hydraulic system must have been running half a century ago. It was on the market by '54. Just think of the investment in the tooling to mass produce that stuff for years. You couldn't afford to develop it these days and all the hydractive systems and correcting spheres that can be thrown at it only serve to show how right they got the original design.

tomsheppard · Post by **tomsheppard** » 13 Jul 2003, 03:32

Just a thought, The air would doubtless be at very high pressure and thus not very elastic. Its spring rate would probably not affect a correctly inflated set of spheres. The brakes might be expected to suffer or the steering feel, perhaps.

AndersDK · Post by **AndersDK** » 13 Jul 2003, 04:23

Tom -
It's known that air in suspension on hydraulic Citroens causes a hard suspension "feeling" - it feels bumpy at roadspeeds.
Not knowing the mathematics of suspension - I suppose the air does in fact impact the spring action - since the air is located in the fluid - acting as an unwanted spring element outside the sphere spring element - possibly upsetting the sphere's damper valve function.
The problem is wellknown after wheel sphere replacements - and of course if the pump takes in air. May also be seen after regassing old spheres with leaking membranes - where the sphere quickly (over days or weeks) leaks out the N-gas into the fluid.
"Herhjemme er den danske Statens Bilinspektion" not interested in the clicking interval from the regulator. But they'll probably notice the clicking as a strange noise - and ask if you have noticed this problem - i.e. it's not an MOT issue.
From experience I just don't feel well driving a hydraulic Citroen with fast clicking regulator - knowing that spare brakes pressure relies on a wellworking regulator/acc sphere.

jeremy · Post by **jeremy** » 13 Jul 2003, 04:48

Let me firstly say that only relatively recently has my BX been functioning properly and attaining full pressure. What I kept noticing was that it would behave differently when I fiddled with the system or added some new LHM - even relatiely small quantities would bring about dramatic improvements which would fade after a week or a couple of hundered miles.
One explanation would be that new LHM mashed up and shortened its molecules over a few days so when owrking on it I would try and make sure I didn't loose any and I wouldn't top up so that I could evaluate what I'd done quickly. I'd still get much the same effect and came to the conclusion that the difference must be due to aeration of the LHM on re-fitting the pump feed and priming. Incidentally having cured my problem and attaining full pressure a top up after a few days didn't seem to make any difference at all!
Jeremy

alan s · Post by **alan s** » 13 Jul 2003, 16:58

It's a bit hard to tell if the pump & hose clips have improved the ride much as I also had the spheres regassed at the same time. I have noticed however that the brakes are now really deadly (as CX brakes should be), the steering still has the power there (not 100% but still there) at idle and the ride no longer thumps on harsh bumps. The best description I can make is it now feels like a CX. The handling is grouse but again, I've just fitted new tyres but due to the fact that this car gets more abuse than use, I only fitted local El Cheapos but they ride, brake & handle like the top of the range stuff...I'm really chuffed about the whole thing.
Intend fitting a set of replacement front wheel cylinders soon which I think will improve the ride & handling even further. Just got back from an 800+klms round trip and left the car sit for 1 1/2 hours, went out to put it in the garage & it hadn't dropped 1 centimetre!!
Have had a couple out here who won't have it that it can be anything but the pump, but I won't swallow that...to me it's not logical.
Alan S