The following are a series of messages I recently posted on another forum which unfortunately does not have an archives section, hence they are going to be lost if not retrieved & stored here.
Whilst at first they may appear to be somewhat disjointed, the reason being that they are in response to several different requests for help.
They deal with problems such as "how can I get the fluid out of the brake lines" "I suspect I have air in the hydraulic system" and "my hydraulic system is contaminated with dirt."
By reading the responses, I hope that it may answer questions about the perceived "mysteries" of a very basic piece of engineering; the hydraulics of the BX. Even if you don't believe the problem described is shown here, then perhaps the solution will be.
There is a bleeder at each brake and one on the brake valve. My thoughts are on bleeding that too little time & effort is put in to this part of the operation. Whenever I bleed any Citroen (I own a couple of CX's as well as the BX) I usually do them at least twice & give the suspension a work out between one bleeding and the next. This can theoretically release any air or garbage in the suspension.
Firstly clean the area around the bleeding nipples thotoughly. Use new plastic hose & a clean jar. The initial bleeding normally produces contaminated LHM which is discarded. Second time around if clean work practices are involved, the LHM can be returned to the tank & bleeding can be as long as you want it to be. Remember to nip off bleed screws whilst the assistant still have their foot on the brake.
I have even seen it done that long lengths of plastic tube is used for the front brakes & after the initial bleed to get rid of rubbish, these tubes are fitted & placed in the LHM tank & the contents simply "circulated" to rid it of all air.
Also check the return line to the pump from the tank is sealed off & is not cracked or hard as this can give an ongoing problem with air contamination.
Just remember that you collapse the suspension, then slacken the 12mm bolt on the regulator/accumulator & leave it loosened. Remove the tank, drain it & clean it, don't lose the white plastic disc on the bottom of the tank (this MUST be removed to clean the tank properley.) Clean the two filters (one half moon shape in cross section whilst the other is cone shaped) Wash the filters the fittings and the interior of the tank with clean petrol. BEFORE you put your hand in the tank to wash or wipe, inspect the metal lip which your hand has to go through at the opening - IT IS RAZOR SHARP !!
Place the tank back in position & half fill with LHM. Refit filters to block, look at ball bearing that has fallen out & convince yourself that it shouldn't be there refit the block to the tank & the retaining clip to hold the tank into position. Prime the intake (or supply) line (approx. 12mm black hose that goes from the tank to the pump.) by pouring LHM into the hose via a funnel. Tighten the 12mm plug on the regulator/accumulator and reset suspension height via the height adjustment lever in the car. Fill the tank about 3/4 full with LHM. If the car refuses to rise, switch off motor & prime the intake again (start the car if necessary & then quickly refit supply hose to tank as soon as the pump starts operating.
Now a point to remember; the brakes are dead ends so the old or contaminated LHM is still in the lines to the 4 brake calipers. When you bleed them, you will find the liquid a dirty colour which will progressively turn to the bright green of fresh LHM as the old stuff is pumped out. This must be discarded. This will be an amount of approximately one litre combined, which you will need to get rid of. This is why I said 3/4 fill the tank. As described below, the ideal set up is 3 people doing the bleeding. When completed, make sure that the LHM tank is correctly filled which I personally judge by being able to touch the level with my index finger when put in through the filler hole when the car is running and the suspension set on normal ride height.
The three people bleeding system is quite simple & does not require all 3 to know "all about cars."
#1 In the drivers seat starting the motor & putting the foot on the brake pedal when requested.
#2 Standing at the side of the car shining a light into the LHM tank & topping up as required.
#3 Doing the rounds of the wheels doing the actual bleeding.
Whilst 3 may not be mandatory, it just makes the job so much less hassle free & prevents little accidents like forgrtting the fluid level & sucking a heap of air into the system, kicking over the LHM drum as you race from one side of the car to the other in case the tank runs dry etc.
A recent suggestion of bleeding the hydraulics & filtering through a filter medium (I suggested a swab made from old pantyhose) just may be worth considering if dirt is circulating and causing an intermittent problem.
As I said at the outset; I hope it is not too disjointed so as to tend to confuse more than assist. I would suggest that this information should be looked at to assist anyone who has never changed their LHM, cleaned their filters or bled air from the system or for those more experienced DIYers who may have simply overlooked something & this may help to jog your memory.
Alan S