ACTIVE BODY CONTROL SUSPENSION
Vehicles with Active Body Control or ABC have several issues to be concerned with. This system is a fully active hydraulic system driven by a high pressure tandem pump that also controls power steering. These systems are prone to leaks and seeps but are overall very reliable with leaks at the pump or internally through th valve bocks being the most common. Pump leaks at the pulley snout require replacement of the pump. The vehicle level or bank in a turn is controlled dynamically in real-time using inputs from four level sensors and vehicle accelerometers. by routing high pressure fluid, delivered through front and rear valve blocks, to struts at each wheel. The system also has several nitrogen accumulators for dampening fluid pressure fluctuations. The valve blocks have valves with o-rings these can be prone to leaking if the fluid has fine particles of dirt in it or as the seals age. It is recommend to flush the system fluid periodically and change the filter as he fluid deteriorates over time.
If the ride height changes after shutdown persistently a fluid flush alone may not resolve the issue. The respective axle valve block may be the issues, internally leaking oil back to the reservoir. The ABC and power steering system uses several gallons of Pentosin CHF 11S hydraulic fluid. These systems are complex and diagnosis and testing should be conducted before commencing any repairs. The ABC struts have quick release connectors, given where they are located corrosion someimes prevents removal requiring the corresponding hard lines to be replaced. Never work on these systems when they are pressurized the lines have pressure bleeds near each strut and other lines can be depressurizing by cracking the line open carefuly. In many cases they are self-bleeding but several test modes are available for these systems that can be used for diagnostic purposes as well as insuring bleeding is complete. Rodeo is the most widely used and creates a rotational cycling of the strut height. This type of motion is very efficient at flushing the system. To flush run the return line into a 5gallon bucket and run a rodeo until it’s half full of dirty fluid or until the fluid runs green, while running a rodeo. Monitor the pressure stop and allow it to build if needed and do not run the pump dry. Prime the pump by lightly pressurizing the fluid container with compressed air, this is not a pressure vessel don’t explode the container.
We have had many inquiries about remanufactured pumps. I’m sure rebuild quality varies but given the pump is small and produces 200bar max pressure, and it takes considerable time to install one, we only use new OEM pumps. If you think you need to replace the ABC pump proceed only if it’s leaking from the pulley area, and or fails a pressure test, when the fluid level is correct and the low pressure concern is reproducible. If it’s just noisy and you think it’s the pump have it diagnosed by an independent specialist or the dealer before proceeding, there are often instances where the noise is not the pump.
Call us if you are having problems with your ABC system and want to schedule a service appointment.