engine oil BMW 740IL 1998 E38 Level Control System Manual

4
Level Control Systems
Hydropneumatic Rear Leveling System
This module pertains to the hydropneumatic rear suspension system with the engine dri-
ven piston pump. The earlier system using the electro-hydraulic pump will not be dis-
cussed.
The self-leveling suspension system is designed to maintain vehicle ride height under
loaded conditions.
The system is fully hydraulic, utilizing a tandem oil pump to supply pressure to both the
suspension system and power steering system.
The system is installed on:
 E32 - 735 iL, 740iL and 750iL
 E34 - Touring 525i and 530i
 E38 - 740 iL and 750iL

9
Level Control Systems
Control Valve
The rotary control valve located on the rear suspension has three positions:
 Raise
 Level
 Lower
The control lever is attached to the rear stabilizer bar to sense vehicle loading. When the
vehicle is loaded (passenger or luggage) the suspension drops and the stabilizer bar twists.
The control lever is moved in the "raise" direction.
With the engine running, oil flows from the pump to the bottom of the rear struts. The body
of the car is lifted and the control lever returns to the level position.
In the level position, the oil
bypasses the valve and
returns to the reservoir
through the return line.
A minimum pressure of
440 Psi (30bar) is main-
tained at all times. If ser-
vice is required, a bleed off
valve is installed on the
control valve to drain the
systems pressure.