BMW E34 Website

Level Control Systems
Purpose of the System
The primary function of Level Control Systems is to maintain the height of the vehicle as closely as possible to a predetermined level under all load conditions. This constant level allows the suspension system to maintain the alignment geometry.
Camber and Toe in are minimally affected when the ride height is consistent. In addition, the headlight range stays consistent throughout the various operating conditions.
The Level Control System is designed to operate in the event of static changes such as when passengers are entering or exiting the vehicle or quasi-static such as s when the fuel tank is emptying while driving.
The Level Control System come in various configurations such as hydraulic (hydropneumatic) or pneumatic only systems.
Hydropneumatic systems use high pressure hydraulic fluid which is dampened by a gas cushion from a nitrogen charged accumulator. These system use and electro-hydraulic pump or an engine driven piston pump. These systems are installed as follows:
• Hydropneumatic Level Control System with electro-hydraulic pump - This type of system is used on the early 5 Series vehicles (E12 and E28), the 6 Series (E24) and the early 7 Series (E23). This system uses an electric motor, pump and an expansion tank which is connected by hydraulic lines to the rear spring struts.
The rear spring struts are also connected to a pair of pressure accumulators which are “Nitrogen Charged”. There is a control switch which mounted on the rear axle which monitors the position of the stabilizer bar. Changes in ride height are detected
and the system is regulated to maintain the correct level. During prolonged dynamic movements during acceleration and braking, the level control system is disabled by an acceleration sensor (mercury switch) and brake light input to the hydraulic control unit.
• Hydropneumatic Level Control System with engine driven piston pump - This system can be found on the 7 Series (E32 and E38) and the 5 Series Touring (E34).
This configuration is similar in operation to the previous system with a few changes.
There hydraulic pressure now comes from an engine driven piston pump. This pump is mounted in tandem with the power steering (radial type) pump. The pressurized fluid is sent to a control valve which distributes the fluid to the rear spring struts and pressure accumulators. The control valve is attached to the rear sway
bar by a lever, changes in ride height will move the lever which will influence fluid flow to the spring struts.
The next generation of BMW Level Control Systems evolved into pneumatic only systems which are referred to as EHC. EHC will be discussed later in this module.

Hydropneumatic Rear Leveling System
This module pertains to the hydropneumatic rear suspension system with the engine driven piston pump. The earlier system using the electro-hydraulic pump will not be discussed.
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

System Components
The system consists of the following components:
• Tandem Hydraulic Pump
• Oil Reservoir
• Pressure Reservoir (2)
• Control Valve with Regulating Linkage
• Camber Warning Switch (E32 and E34)
• Rear Shock with LAD Module
• Expansion Hose, Pressure Lines and Distribution block.

Tandem Pump
The tandem pump consists of a vane pump for power steering and a radial pump for selfleveling suspension. Both pumps are driven by the same shaft and have separate oil feeds for each system.
The radial pump has the capacity to pump 102 liters of oil per minute. The maximum pressure is limited to 1900 Psi (130bar) by the pressure regulator located on the control valve.

Oil Reservoir
The single reservoir stores fluid for both the self-leveling and power steering systems.
Incorporated in the reservoir, is a reed type level warning switch. If the fluid level drops and the contact closes, a signal is sent to the check control module and a warning will be displayed
in the instrument cluster matrix display.
The hydraulic fluid required for the self-leveling suspension system varies between models and installed equipment. The following fluid is used:
• Pentosin CHF 7.1
• Pentosin CHF 11S
• Power Steering Fluid (BMW)
This type of fluid is used because of its low viscosity and low noise characteristics. It cannot be mixed with other fluid
types.
The self-leveling system fluid type is always marked on the top of the hydraulic reservoir. Always use the correct fluid never mix with another fluid.
When filling the system, be aware of the status of the level control system. If the vehicle is loaded, the level will appear to
be low. Do not fill the system unless it is in the resting state. Otherwise, an overflow situation could result.

Pressure Reservoirs
The oil pressure reservoirs (2) on each strut incorporate a membrane and are nitrogen gas filled. They are designed to absorb the oil which is expelled from the struts during downward movement, the gas in the reservoirs is compressed and pushes the oil back into the
struts during upward movement.

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 maintained at all times. If service is required, a bleed off valve is installed on the
control valve to drain the systems pressure.

LAD Module
The load dependent module is a control valve that regulates the flow of oil between the strut and the pressure reservoir.
The control piston in the (LAD) moves in relation to the pressure applied from the pump.
This movement will regulate the tension on the inner spring of the module. With only a low pressure applied, a small amount of tension
will be applied to the spring. Little flow resistance will be developed between the strut and pressure reservoir. The damping force is soft.

With a high pressure applied to the control piston, the flow resistance is high and the damping force will be stiff.

Camber Warning Switch (E32 AND E34 Touring)
The self-leveling suspension systems used in the E32 and the E34 Touring are equipped with a camber warning switch. The switch is mounted on the right rear axle support and connected through a rod to the semi-trailing arm.
The function of the switch is to warn the driver of an overload condition or an unsafe driving situation.
If the switch detects a rear wheel camber of -3.5 deg. A signal is sent to the check control module and displayed on the dash.
A time delay of 8 minutes is incorporated to prevent the warning from being displayed while driving through turns.
The E38 does not use the camber warning switch due to the design of the rear suspension.

Ride Height Measurement
When checking vehicle ride height with EHC, measure from the lower edge of the wheel opening to the center of the wheel hub.

Spurred on by Roger Neef’s arrangement of the group purchase of Sachs Sports Suspensions from Bekkers, a few of us Touring owners went looking for complete information on how to get our Wagons closer to the ground. As it happened, we were unable to get in on the Sachs purchase. Since those kits are built around Eibach springs, and Ebiach makes NO springs for the Touring wagon, we were out of luck. Other options were found, one rather mild, one a bit more wild.

On the mild side, BMW makes a Sport suspension for the E34 Touring, in the spring table, they refer to it as the "Low Slung Sport Suspension." These are conservative sport springs with a .5 - .75 inch drop, matched to our cars and tuned by BMW. These springs will give a drop similar to the drop seen on the factory M-Technic suspension, or on the Dinan stage I suspension kits. I have not worked out yet whether there are BMW factory shocks that go along with these springs. There are many aftermarket shocks available in different firmness that should match your desired manner of driving. Paul at Maximillian Imports can get any and all of these springs for us, and his current prices are $279 for a set of 4 springs.

Part numbers below are from the E34 Spring table. In the notes that follow, numbers used are the last 3 digits of a spring part number. Things to consider when dealing with BMW spring part numbers –

(All with description Low Slung Sport Suspension, AC, CD Changer, Dual Sunroof, power seats, cargo cover & nets, roof rack, +50KG rear load)

Here I list the "Low Slung Sports Suspension" spring part numbers for our Tourings. The part number listed is the part number returned from the spring table, the numbers in parentheses are the part number range available. Based on the notes above, you could increment or decrement the part number given to find a slightly lighter or heavier spring for your taste.

525iT - front - 31 33 1 138 810 (808-812)
rear - 33 53 1 138 779 (778-779) (with self level)
rear - 33 53 1 138 720 (719-721) (NO self level)

530iT - front - 31 33 1 138 812 (808-812)
rear - 33 53 1 138 779 (778-779) (with self level)
rear - 33 53 1 138 720 (719-721) (NO self level)

On the wilder side, H&R makes lowering spring kits for the Touring wagon in it’s self-leveled (1992-1993) and un-self-levelled (1994-1995) forms. The H&R kits will drop the front of the Touring between 1.5 and 1.7 inches, the rear drop will be between .5 and .7 inches. This will be a nice, low, tight ride. There are no matched shocks available for these kits, but they are generally sold with Bilstein Sport shocks. BMP should be able to work a kit out if those are the components you desire, they list many of what they call the HRB kits, though you will have to call them with the H&R part numbers listed below. TMS quoted prices of $239 for the Touring springs WITH self level and $269 for the Touring WITHOUT self-level (the self-level kits are in stock and not currently a special order item). As with BMP, you will have to have these part numbers in front of you when you call, as they are NOT in the TMs computers. H&R DOES NOT LIST THESE SPRINGS ON THE PARTS LIST AT THEIR WEB SITE, call them if you want to verify the part numbers.

Part number #29888-1 IN STOCK $239.95
(Lowering springs for Touring, WITH SELF LEVEL!!! Drop = 1.5-1.7"fr/0.5-0.7"rr)

Part number #29889-1 In Germany – never ordered for US ~$270
(Lowering springs for Touring – NO Self Level – same drop, not in stock, can order)

Bilstein sells (at least i Europe) a lowering kit for the E34 touring which lowers 25mm in the front and 20mm in the rear. I just bought one of theese kits, and it includes front and rear Bilstein sport dampers, and springs, made by Eibach (says so on the springs)

B12 - Tuning-Kit SE5-8094 Komplettfahrwerk (520i)
B12 - Tuning-Kit SE5-8096 Komplettfahrwerk (525i and M-tech)

This includes the following dampers:
B8 - Sprint (US Sport)
B46-1486 hinten Stoßdämpfer
P36-3020 vorne Patrone (520i)
B8 - Sprint
B46-1486 hinten Stoßdämpfer
P36-3019 vorne Patrone (525i and M-tech)

As it turns out, BavAuto has instructions on their website for how to implement the Self Level Elim kits that they sell. Instructions are found in a PDF file . The instructions look pretty straightforward regarding the removal of the system. Look at your Bentley Manual for other information not included in the Self Level Elim Instructions including (but not limited to) de-pressurizing the system, spring/shock removal and refilling/bleeding the system.

Paul at Maximillian Imports quoted me $125 for a self level elimination kit that includes upper shock mounts, spring dampener pads, buffer stops, lock nuts, dust sleeves and upper mount paper seals. This would be desirable to avoid destroying the rear upper shock mounts when the new standard shocks are installed.

Who makes the BavAuto springs? I got no well-defined answer from BavAuto product support, though they are made in Germany, NOT H&R, NOT Eibach.

Credits: Thanks to Roger for getting the juices flowing on this. While we could not take part in the Sachs purchase, I don’t know if I would have started calling around without his work. Curt Anderson gets the credit for the first set of calls to H&R, between the two of us, we finally got the whole poop on what H&R springs are offered for the Touring in it’s various forms. A HUGE thanks to Paul at Maxmillian Imports, possibly the only man in the country who knows what the BMW Sports Suspensions are all about. I called a number of dealers with the part numbers and descriptions of the Sports Suspension springs and got the same answer, "I can order them, but I don’t know what they are." Paul knew what they were right off the bat, and can source them at a great price. Any other Q’s you have regarding your undersides, he is the man to answer your questions and get the parts.