Citroen BX brakes only work if steering full lock!

Lava · Post by **Lava** » 01 Jun 2004, 20:54

Bought a Citroen BX ("J" Registered- 1991/92) and have discovered that the brakes only work if the steering is on full lock!
No-one seems to know what is causing it - anyone any ideas?[:)]

tomsheppard · Post by **tomsheppard** » 01 Jun 2004, 21:02

It sounds like a flow distributor problem to me. This bit splits off the steering pressure from the suspension/brake circuit. What does the suspension do? If it works ok then maybe a pair of pipes have been swapped. Either way, it will take a little diagnosing and some testing carried out.

Lava · Post by **Lava** » 01 Jun 2004, 21:23

Suspension works ok. You don't happen to know where I could get a plan of where each pipe should go?

AndersDK · Post by **AndersDK** » 01 Jun 2004, 21:45

On this schematic (right most for servosteering option) :
http://citroeny.cz/servis/bxser/hydraulika_schemata.gif
- you find the FDV (Flow Distributor/Diverter Valve) as item 17.
Item 18 is the steering pinion valve, item 19 the steering ram cylinder.
Further : item 2 is the hydraulic (belt driven) pump, item 3 is the PR (Pressure Regulator), item 4 is the accumulator sphere (fitted on PR).
The FDV is located on front flange of the gearbox, a square(ish) device with the 2 pipes at top, 3 at bottom, as shown on schematic.
The PR with it's accu sphere is found below, fitted on engine block.
Finally : it does not matter which BX model (engine type), as there are only 2 options : with - or without - servosteering fitted on all BX models.
Surf the page for more BX info [;)]

DLM · Post by **DLM** » 02 Jun 2004, 05:29

I also think there's a good BX hydraulics PDF on Bob Smith's site, which includes the flow diverter disassembly/reassembly diagrams. Referring to that may tell you quickly if any pipes have been swapped. If the BX is a fuel-injected petrol model then don't hang about - remove the radiator for full access to the flow distributor.

AndersDK · Post by **AndersDK** » 02 Jun 2004, 13:37

Yep David,
Bob Smith's FTP page offers excellent BX info :
http://www.rwbsmith.plus.com/citroen2/H ... aulics.pdf

jeremy · Post by **jeremy** » 02 Jun 2004, 19:08

I'm almost certain its FDV having had similar problems myself. With no pressure on the steering wheel the valve is supposed to allow a small amount of fluid to the steering rack which in return allows it to return to the reservoir. When the wheel is turned this flow ceases and the FDV is supposed to operate so as to allow a greatly increased flow to the steering to operate it. This is done by the top slide valve.
operating the steering causes another part of the regulator to operate ad i think itpresssurises a return pipe from the regulator. This causes the pressure in the regulator to rise and it begins to function.
I had a similar problem with my TD BX which would mysteriously put the warning light on after it had been driven a mile or two. The car would not rise properly although the brakes always worked, but I could get it to rise and work nearly normally by holding the steering against load. I eventually traced it to an incorrectly assembled pressure relief valve in the FDV and since re-assembly it has worked properly without further problems.
The valve in question is black painted ins isn't genuine. I overhauled a genuine one with the overhaul kit and that didn't work properly so I must have got something wrong there.
Ideally buy a new one or substitute for known good. Otherwise take it off, check the relief valve (under the screw in plug in the middle of one side - keep the setting!) and chuck it in a bucket of petrol overnight - it may soften up some crud and allow the slide valve to move. What is more likely is that it has injested its top filter and this is clogging it somewhere in which case dismantling may be the only cure.
the correct order for the valve is ball bearing, support, spring, plug. On mine the support and the ball were the wrong way round.
Jeremy.

Lava · Post by **Lava** » 05 Jun 2004, 22:00

Thanks everyone problem solved - 2 pipes had been swapped and bent to fit (!?)
Lava

alan s · Post by **alan s** » 06 Jun 2004, 02:58

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Lava

Thanks everyone problem solved - 2 pipes had been swapped and bent to fit (!?)
Lava
<hr height="1" noshade id="quote"></blockquote id="quote">
I met an old retired hydraulics engineer a while back and the topic of FDVs and reconditioning them came up. He never stopped telling me how he does quite a few of these up for various Cit repairers and how often he gets them returned "Faulty" after he's redone them.
Every time, he attaches a note saying "check your connections" and he was very insistent that when removing one from a car the fittings must be marked as it is ever so easy to reconnect the wrong way around.
This I suppose proves his argument!![B)][:o)]
Alan S [:D]

Lava · Post by **Lava** » 07 Jun 2004, 00:17

Exactly Alan - Bob Smith's info was the best, but if anyone has a similar problem you can e-mail me Brian@bgregg.freeserve.co.uk, Thanks Lava