Citroën BX – Hydraulic Service – Changing the LHM

2 min read

After catching some leaking fluid from the rear suspension and bleeding the brakes, it became apparent all was not well with the LHM suspension fluid. The liquid should be bright green and not a sludgy yellow/brown colour. It was time for changing the LHM in the Citroën BX.

Tank out of the Citroën BX, drained and ready to clean and change the LHM
Tank out of the Citroën BX drained and ready to clean and change the LHM

Typically, the LHM discolours with age, pipe breakdown, and moisture inclusion. It also absorbs moisture from the air, usually at the reservoir. The mineral chains also break down as they are repeatedly forced through very tight channels. Combined, these things lead to the fluid becoming thin, discoloured, and ultimately poor system performance.

In time-honoured fashion, the filters were gently cleaned in petrol. Unfortunately, these are the worst filters I’ve seen in a running car. Unusually it took several passes to get them clean.

With only a light cleaning, the petrol is saturated in'filth'
The petrol is saturated in ‘filth’ with only a light cleaning.

Given how filthy the filters were, I wasn’t surprised to find so much sludge in the bottom of the LHM reservoir. Clearly, this Citroën BX needed the LHM fluid changing and was well overdue. Unfortunately, it took a surprising amount of elbow grease to get the filth out. Fortunately, I have an old toothbrush with a bent neck perfect for getting into the edges. But, of course, a set of gloves is also a must!

Before and after of the bottom of the LHM reservoir
Before and after image of the bottom of the LHM reservoir

Rather than LHM, I’m going to spend a year or so running ‘Hydraflush’ from Pleiades, something I’ve had in stock for a long time. It’s slightly darker than regular LHM and will help pull out some of the filth in the components.

The car is probably well overdue for a full re-pipe as well.


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