The introduction of Hydractive 3 to Citroen (with the first generation C5) brought about a radical change in the established hydraulic orthodoxy of past Citroens. No longer were the suspension, steering and brakes linked by a common hydraulic system; these systems were segregated in the name of efficiency, simplicity and potentially safety. On the C5 X7 there are two self contained electro-hydraulic pumps located in the front drivers side wing that supply hydraulic fluid to the suspension struts and powered steering rack when requested. The pump supplying hydraulic fluid to the suspesnion and controlling the ride height is a single unit called the Built-In Hydraulic Unit (BHI)
Whilst both pumps are incredibly reliable, a not uncommon problem with the suspension pump is the blowing of the 40Amp fuse that protects it. For me this happened for the first time (June 2018) on a holiday trip to France; some 50 miles away from the very factory the car was built in! At the time, the refusal of the car to rise to the correct height was very concerning and threatened the trip. Fortunately I bypassed the fuse temporarily at the start of each journey with some 4mm² cable I had in the boot. Upon returning home I decided to remove the motor pump and have a look inside.
It had been suggested on the frenchcarforum.co.uk that the dust from the carbon brushes can come into contact with hydraulic fluid and create a conductive paste that can cause excessive current draw by shorting out the windings.
The first step was to remove the BHI assembly from the car:
The wheel arch liner was removed and the pipe from the Fluide LDS reservoir to the powered steering pump was located. This pipe was removed and the LDS drained into a suitable container.
The next step was removing the BHI itself:
The two pipes circled in red which are the hydraulic link to the front and rear suspension struts were removed in addition to the low pressure LDS tubes. After that, the bolts holding the BHI in were removed and the unit was lifted out.
Immediately visible upon the removal of the motor endcap was the amount of ‘carbon paste’ that had built up.
Using a mixture of brake cleaner (Acetone/heptane) and compressed air, the motor brushes were cleaned and the brush housing replaced on the motor. The commutator was also cleaned in the same way
The cleaned motor brush assembly was reinstalled and the BHI reconnected to the car. The LDS reservoir was topped up with fresh LDS and a new 40A fuse installed in the engine compartment fuse box.
As of Aug 2019, a year has passed since this fix was implemented and the suspension pump has performed perfectly ever since!