There are numerous threads (listed at the bottom for reference if required) on this forum mentioning the common problem with the Doseur Valve so I've had a good read but can't find a complete start to finish thread so maybe I could try one I've read that it's possible to replace the cap in situ and also that it's possible to replace the cap without removing the Doseur Valve completely from the vehicle, one even saying it was possible to replace the leaky cap in situ This wasn't possible for me despite prolonged attempts.
Symptoms - LHM+ level repeatedly needs topping up despite there being no obvious leaks under the car ?
Signs - Remove the lower driver's door seal to allow the carpet and foam underlay to be partially lifted, if you can see or feel LHM+ fluid, you have found your leaking fluid.
This senario indicates a leaking protective cap on the Doseur Valve (Citroens super brake servo), which needs to be replaced urgently. To minimise further fluid loss I used a bungee to lift the brake pedal up a couple of inches towards the steering wheel and after parking the car in your repair area, not too close to the wall (!) as you will need to bleed the system later, I supported the front of the car so the front wheels could be removed for brake bleeding. Set the vehicle height to low, once the car is settled, release the remaining pressure in the system by undoing (half a turn MAX) the pressure release bolt on the regulator body (12mm hex bolt). Remove the handbrake cables from the brake calipers is recomended, if you're planning on removing the driver's carpet for cleaning up the footwell area.
Order the parts required:
Brake Protector (rubber cap) 95640047
Alloy Sealing Ring 5424455
3.5mm pipe seals x4 96085785
LHM+ as required
I ordered a kit but you might need No 2 as well if your Alloy Sealing Ring isn't re-useable ?
Chevronics also stock the main part required.
While you are waiting for the parts to arrive, set about cleaning the leak area.....
I decided to remove the carpet as I had plenty of time for the job so ...
I disconnected the vehicle 12 volt battery, to remove the drivers seat, (if you're NOT removing the seat from the car completly LEAVE the trim fitted) remove the seat plastic side trim if removing the seat from the car (pulls up and forward - mine broke), rear bolts first, then fronts (40 Torx bolts) tilt the seat back once the 5 bolts are removed and under the seat is the wiring harness for the airbags (make sure you've isolated the car battery and allow 10 minutes before continuing to allow the sensitive ElecTrickery to become safe) remove the 4 wiring connectors clips and a harness clip (you might have extra wiring for seat adjustment/heater) and the seat belt anchor if you're removing the seat out of the car.
To remove the carpet you need to remove the fixings for the centre consul, I managed to remove the carpet by just loosening the consul, the airbag ECU and a plastic 'clip' that unscrews near the thottle pedal. This was mainly because I hadn't left much room (that wall again) to remove the handbrake cables from the brake calipers, necessary to lift the handbrake lever fully to release the centre consul. Lever out the oddment tray to reveal the airbag ECU (3 10mm hex bolts) and 2 10mm bolts for the consul. Lever out the gear lever gaitor. Remove any switches you have on the rear of the consul and near the height selector (levers out) is a single 10mm hex nut, a further 2 10mm hex nuts are accessable after the rear ashtray is removed. Once all those nuts (5+3) are removed you can wiggle the carpet out from under the consul.
Then the foam can be removed for cleaning/drying (small cut near handbrake required). I used washing powder in a hot water solution once most of the LHM+ was drained then rung out of the foam. My carpet was fairly free of LHM+ but I still wish I'd given it a freshen up whilst it was out of the car.
The engine bay on the HDi allows just enough room to pivot the valve, so I didn't need to tilt the engine at all but you still have to remove a few parts in the engine bay:
Engine cover, mount for exhaust emmision valves, cable plugs detached, also allows one of the air-con pipes to be manouvered out of the engine bay, fuel lines uncliped from securing points also allows better access. The other air-con pipe was left in situ.
Once you've done that, working inside the drivers footwell, remove the carpet trim above the brake pedal, held in place by 4 plugs and one screw, that removed you'll need a good quality 11mm socket on a narrow 1/4” extension bar and knuckle (my long sockets were too long and my short sockets wouldn’t go through the locating / guide horns of the valve body with the brake pedal still attached (still bungied up to avoid constant LHM+ leaking out of the valve.
Undo both nuts that secure the valve to the engine bay bulkhead. I also uncliped the pipe clip on the bulkhead to allow a bit more flexibility in the pipes. Now the valve needs to be rotated forward towards the engine, roughly 90 degrees, this will expose the cap that is the likely culprit for the leak inside the car.
I prised out the alloy ring that secures the cap, mine came out in good condition, (luckily because I never had a new one), once the ring is out the rubber cap needs prying out.
If you want to try and just replace these two parts without further dismantling, feel free to try, my thumbs weren't up to the job and a week later I still have dents in them from trying to press the alloy ring back onto the rubber cap in the valve body, I also tried with a clamp and socket but on the car the ring just wouldn't go in deep enough or square enough, partly because of the 4 pipes and 2 tubes going into the Doseur Valve. Maybe my replacement part is stronger than the previous parts
So unless you have thumbs like superman you'll need to take the Doseur Valve off the car: Remove the 4 metal unions (8mm) and wiggle the pipes out (they'll be stiff to remove because you've twisted them a bit) this will allow the valve to be twisted more to get asccess to the remaining two rubber hoses, be gentle here as they will be delicate, remove the securing clips, slide off the hoses and bung as many of the holes as you can to prevent dirt getting into the system.
Even with the Doseur Valve off the car, I struggled with the clamp tool, to push the ring in square with a socket and it had to be persuaded with a soft mallet on the socket and bar, now assuming there was no other signs of a leak from the other end of the valve you can remove the 4x old seals from the valve body and re-assemble with new seals.
Note: I bought new 3.5mm pipe seals from Automec.co.uk but they weren't as flexible as Citroen originals, which I ended up re-using after turning them around so I used the better end against the union bolt.
If you need or want to strip the Doseur Valve down further I suggest you take a good look at the Xantia007 site for parts, tutorials and technical sheets for LHD models but relatable.
If you're happy that you've replaced the faulty parts succesfully you can now put it all back together.
I had a test run of the system after re-connecting the pipes/hoses onto the Doseur Valve at system pressure to make sure I had got a good seal on the rubber cap, all was good so I then twisted it back onto the bulkhead, held in place with a lump of wood wedged in whilst I tightened the nuts, once fitted I tidied up the metal pipes to remove the distortions caused and re-fitted the pipe clips.
Refitting the seat was a bit of a pain, re-connect all the wiring plugs under the seat first and remember the front left bolt is a fixed position and loosely fit that bolt first, the others all have moveable nuts
Once you've re-fitted everything it's time to bleed the air out of the hydraulic system.
Part of the reason I was reluctant to remove the Doseur Valve from the car was that I'd read it was a pain to get all the air out of the valve whilst bleeding the system. I bled mine as usual, front wheels in the air, rear wheels on the ground, make sure the LHM+ reservoir is topped up throughout the process, run the engine whilst the Regulator Pressure Relief Valve is open slightly, after a couple of minutes idling, this does a good job of removing the majority of the air from the front half of the system, turn the steering wheel lock to lock a few times to replenish the steering rack, (check fluid level again) close the Relief Valve and put the vehicle into high mode, with the engine running and the brake pedal lightly pressed (you might be lucky enough to have a beautiful assistant but i useD a bit of wood braced between brake pedal arm and steering wheel - well.. for this job anyway) my bleed kit is a litre coke bottle, clear brake bleed hose and a good narrow 8mm spanner, an old large oven tray or baking tray under the wheel you're bleeding to catch the spillage if your bleed hose pops off the nipple
Bleed the rear right, then rear left, I manage (fiddly) these through the slots in the wheels on my car (you might need to remove the rear wheels for access) but make sure you support the weight of the vehicle on the suspension arm to fully bleed the rear hydraulic lines. Open and close each respective bleed nipple, one at a time. LOTS of LHM+ with micro bubbles of air will come through the rear lines. Once each nipple runs nice clean bubble free fluid move on to the next in the correct order. I bled the front through the calipers to be sure but didn't notice any air in the fronts system, but wanted to be sure so, front right and finally front left were bled (and handbrake cables re-fitted if you removed them )
Remove your supports so the car is still in high mode but on level ground, leave the engine running whilst you complete a couple of Citrobics cycles (High to Low - Low to High) then CHECK your LHM+ level through the sight glass on the LHM+ reservoir, the orange disc should be between the two red lines whilst in HIGH mode on level ground) Once the level is correct set the height to Normal and allow the car to adjust, check under and in the car for any fresh leaks
All being well you're ready for a road test .... Good Luck
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Last edited by Skull on 15 Nov 2023, 11:48, edited 1 time in total.