Changing the LHM Fluid

Why?

The LHM fluid is a liquid hydraulic oil. In your Citroen it provides both lubrication as well as the required pressure (produced by the pump) in order that the PAS, brakes and suspension operate correctly. Over time and mileage, the LHM becomes contaminated by dirt inside the steel pipes, plus disintegration of the rubber seals. In the "good old days" the LHM change was on the service schedule at 24,000 miles. Unfortunately, this is often neglected, and can cause all sorts of problems such as heavy power steering, (blocked flow valve) and sticky height correctors.

Anyone acquiring a BX should look to changing the LHM fluid.

There are two ways.

1) The easy (and cheap way) NOT SO GOOD!
This is carried out with the car in the High position, obviously with engine off!
This method is suited to "first timers" and is quick and easy as you'll only need one small screwdriver, some cleaning fluid and about 3 litres of LHM.
The disadvantage of doing the LHM change with the car in High is that not all the LHM returns to the tank, so dirty fluid will mix with the new stuff. The good news is that you won't need to prime the pump or have the car jacked up.

Method:

Car in High Position, engine off. Remove the metal securing clamp that goes around the LHM tank, it unclips from the bottom. Then carefully remove the plastic centre of the tank (the bit with all the pipes attached). Have rags ready to mop up spilt LHM. Move the pipes/plastic centre to one side, then remove tank. Drain old LHM into a suitable container. Remove thin plastic disc from inside the tank, and clean with brake cleaner. Clean the inside of the tank with petrol or brake cleaner, and dry inside with a clean cloth. Refit thin plastic disc.
Go back to the car, and look underneath plastic tank centre, you will see that there are 2 filters underneath, they clip into place. Remove these gauze filters, clean with petrol or brake cleaner, and dry. Refit filters and clip into place.
Now refit the LHM tank, and the centre plastic assembly with pipes. Secure tank with the metal strap. Now refill with new LHM+. 2nd ornge disc on level indicator should be above white line on sight glass. Start car, allow to tickover, then move height lever from High to Low a few times to bleed system, then return to normal (middle) height.

2) The Proper Way!
This method is carried out with the car in the LOW position in order that all LHM is returned to the tank.

Method:

Car in High position, engine running. Loosen wheel bolts, jack up car and support securely on Axle stands. Wheels off. Height lever to Low position, then open 12mm bleed on pressure reg 1/2 turn. Allow system to depressurise. Engine off
Remove tank, drain LHM and clean filters as above. Refit tank and add 4 lites of LHM+.
Remove rubber pipe that runs from HP pump to top of reservoir at the tank end, unclip and, holding pipe upright, use a funnel to pour LHM down the pipe to prime the Pump. Height lever in high, spin car quickly over a couple of times whilst pouring LHM down pipe. Refit pipe at tank end. Start car, lever in high then open and close bleed on pressure reg block 1/4 turn for about 10 times. Close valve. Arms should start to drop as the car comes up. Add LHM to tank as required.
Get an assistant to sit in car (running in high) with their foot on the brake, and open bleed nipple on each caliper to allow clean LHM to flow through (NB excercise extreme caution with nipples on rear calipers, they shear off very easily - you have been warned).Ensure all bleeds are done up.Tell your assistant to go make the tea.Refit wheel, nuts etc, and get car off axle stands.
As in Method 1, move height lever from High to Low a few times, then back to Normal to fully bleed the system.

Amendments to above, or other suggestions or Tips? Email the webmaster
W D Forte