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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 5 Series > E39 (1997 - 2003)

E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 11-06-2007, 06:41 PM
aceswerling aceswerling is offline
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Calling all Touring owners

I have a 2000 540 with the sport suspension and 50K miles. I also have the airbags in the rear. My car will softly bounce 5-6 times when I come to a complete stop. It's worse when I calmly stop than when jamming on the brakes. I thought the problem was the shocks so I replaced them with new Koni FSDs. I also replaced the thrust arms while I was in there. The behavior is a little better but it's still there.

I can think of two things it might be. First is that the other suspension bushings are bad. I'd have to replace all of them to tighten them up. Second is that the airbag suspension is somehow mushy and the shocks can't dampen them out. The first seems more likely.

Has anybody else with a wagon seen this? Is mine the only car with this problem?
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  #2  
Old 11-06-2007, 06:43 PM
xjohnx xjohnx is offline
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Quote:
Originally Posted by aceswerling View Post
I have a 2000 540 with the sport suspension and 50K miles. I also have the airbags in the rear. My car will softly bounce 5-6 times when I come to a complete stop. It's worse when I calmly stop than when jamming on the brakes. I thought the problem was the shocks so I replaced them with new Koni FSDs. I also replaced the thrust arms while I was in there. The behavior is a little better but it's still there.

I can think of two things it might be. First is that the other suspension bushings are bad. I'd have to replace all of them to tighten them up. Second is that the airbag suspension is somehow mushy and the shocks can't dampen them out. The first seems more likely.

Has anybody else with a wagon seen this? Is mine the only car with this problem?
my wagon doesnt do this
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  #3  
Old 11-06-2007, 06:52 PM
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jvcajita jvcajita is offline
e39 m5 touring aspirant
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sorry can't help...neither can i direct you to another member. ive never encountered anybody else having issues with the rear suspension.
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  #4  
Old 11-07-2007, 11:59 AM
aceswerling aceswerling is offline
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OK, so we're saying this isn't normal. I had two mechanics say "all of 'em do that." All I know is that BMWs aren't supposed to bounce. Thanks for the info, guys.
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  #5  
Old 11-07-2007, 01:19 PM
jdt10768 jdt10768 is offline
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Mine does not do that. Not much help, but just letting you know.
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  #6  
Old 11-07-2007, 02:02 PM
branndon_b branndon_b is offline
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does it feel like it's braking evenly, like it's not a braking issue huh? i was thinking that if you had 'pulsation' in your braking, you know, like uneven braking, maybe it could be a braking issue. does it do it when the car comes to a complete stop? or is it while slowing down? sorry for all the questions, just trying to help. the branndon
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  #7  
Old 11-07-2007, 09:01 PM
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Touring Dude Touring Dude is offline
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Quote:
Originally Posted by aceswerling View Post
OK, so we're saying this isn't normal. I had two mechanics say "all of 'em do that." All I know is that BMWs aren't supposed to bounce. Thanks for the info, guys.
Bummer! Two bad mechanics in a row.
They are both wrong, wagons are not supposta bounce, mine doesn't!
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  #8  
Old 11-08-2007, 01:23 AM
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jvcajita jvcajita is offline
e39 m5 touring aspirant
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i have a feeling these mechanics were thinking of bags on lowriders...lol *kris kross will make you jump jump, uhuh uhuh!*
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  #9  
Old 11-08-2007, 02:19 AM
Patrick Patrick is offline
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Do you have self-leveling rear suspension?

Does the car sag in any direction at the rear?

There have been some E39 Touring owners here with self-leveling rear suspension problems. And as I recall, the problems were related to the air bags in the rear.

Try doing a search in the E39 for "self-leveling suspension" and see if any of those old threads or posts come up. Or search the username tsaros because I think that he had similar issues.

Just an idea.


.
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  #10  
Old 11-08-2007, 05:56 AM
armstm0 armstm0 is offline
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The only thing I can think of is problem with the air springs in the rear - is the ride height OK? I had a leak in the air springs and had to replace them, but the car was sat really low at the back. Definitely not normal for them to bounce.
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  #11  
Old 11-08-2007, 01:55 PM
Jase007 Jase007 is offline
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Quote:
My car will softly bounce 5-6 times when I come to a complete stop.
The front of the car or the rear?

Quote:
I thought the problem was the shocks so I replaced them with new Koni FSDs. I also replaced the thrust arms while I was in there.
FSDs on the front and the rear?

FWIW: The rear airbag sport suspension wagons [528 or 540] have a very strong(ly) dampened [high resistance] OEM SACHs shock in there. It is a strong(ly) dampened shock b/c of the short travel distance allowed by placement [designing in the flat wagon floor].

I recently pulled my OEM rear shocks out when replacing blown fronts [~150,xxx miles] and the old rears were neary as stiff as the new BMW SACHs shocks I was putting in there.

I know there are other touring owners that have successfully installed Koni FSDs on self-leveling / airbag equipped cars ... and reported firmer dampening than what they had in there. What we don't know is if the self leveling airbags somehow move the FSDs [or other aftermarket shocks] out of their intended range of operation. They [Koni] won't say... and I have asked directly.
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  #12  
Old 11-08-2007, 09:35 PM
aceswerling aceswerling is offline
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Yes, it has the airbags in the rear. No, they don't sag to one side. You hear the air pump humming when you start the car but it only runs for a few seconds. I don't think that's the problem.

Yes, I installed shocks/struts in the front and rear. The entire car bounces, not just the rear. The bit about the high damping rear shocks is interesting though. I didn't know about that. The Koni site says the 540 Touring kit isn't for rear air bag cars. The problem is that *all* 540 Tourings have rear air bags so they're contradicting themselves. Perhaps I have a problem with the rear shocks now since they're not the OEM Sachs units. Again, the bouncing seems to be better than before I installed them. It's just still there. I think the problem *is* related to the suspension somehow. Again, I'm guessing bushings since you guys don't have the bouncing problem and I just installed brand new shocks.

No, I don't think this is a brake problem. I had warped front brake rotors so I replaced those. They're not grabby at all so I don't think it's a caliper problem.

One of the mechanics had no clue. The second mechanic was a BMW master tech. He actually felt the bouncing. He just didn't know if the bouncing was normal for these cars. Now I can tell him it's not. That'll allow him to troubleshoot the problem instead of wondering whether I'm imagining things. The only trick with this guy was when he asked if I could live with it instead of fixing it. I told him I'm an engineer with OCD and BMWs aren't supposed to bounce. No, I can't live with it. :-)

Last edited by aceswerling; 11-08-2007 at 09:40 PM.
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  #13  
Old 11-09-2007, 04:05 AM
Jase007 Jase007 is offline
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Quote:
Again, I'm guessing bushings since you guys don't have the bouncing problem and I just installed brand new shocks.
Looking at ETK and bentley for a 540 wagon ... it doesn't look like the bushings in the back [rear subframe bushings] or the front would have enough play / range to allow for "bouncing". I've replaced worn subframe bushings on E30 and E36 cars and there certainly wasn't any "bouncing" when they were failing. RWD steering / shifting = yes, bouncing = no.

Are the front springs OEM std, OEM sport, aftermarket?

Bouncing, as you probably already know, is the mismatch of compression / rebound dampening on the spring. Either the FSDs aren't strong enough / designed for the springs you actually have in there or their "bounciness" [lack of dampening] at low frequency is intended.

From what I've read on them ... it seems their dampening is matched to frequency with a higher frequency receiving more dampening [short / long distance and fast piston movement]. Maybe that is the way they are at low & slow frequency piston movements [like coming to a stop].

I can tell you that after my BMW OEM SAChs sport suspension refresh .. I was / am disappointented with how soft the BMW "sport package" actually is. The front spring rate is to low for my tastes and matched SACHs sport shocks are to soft. To bad Koni doesn't have a std. yellow sport single adjustable [rebound only] shock / strut for this car. I have them on my other two BMWs with matched uprated springs and run Konis on my track car. Love 'em.

Quote:
You hear the air pump humming when you start the car but it only runs for a few seconds. I don't think that's the problem.
You might be on to something here. The PO of my touring replaced one of the R air springs and not both. I am replacing the 2nd one soon. My car also pumps up the rear air bag(s) after sitting overnight. In my case I might actually have the old air spring leaking and the pump running intermittently while driving trying to maintain a set pressure but don't hear the pump while driving. In your case, an air spring may be leaking and the pump is compensating [to get to set pressure] all the while varying the "spring rate" of the air spring that the FSDs are trying to control.

For ha-ha(s) I think I might rig up a LED / light on the air pump circuit to see when the pump is running while driving. There is very little documentation out there on the programming / operation of the pump / height controls.


Quote:
I told him I'm an engineer with OCD and BMWs aren't supposed to bounce. No, I can't live with it. :-)
LOL

I can take a pic of what F spring I have in there but mine is a 528iT [different part]. Another 540iT owner can probably provide you with a pic of their OEM installed front spring. Perhaps from that you can tell if they are stock or something else.
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Last edited by Jase007; 11-09-2007 at 04:14 AM.
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  #14  
Old 11-09-2007, 09:05 PM
aceswerling aceswerling is offline
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I have the stock sport suspension. The pro-Koni struts/shocks were stock from the factory. I follow your thinking about mismatched springs and shocks. If that were true, I wouldn't have had the problem *before* swapping in the Konis. The bouncing also wouldn't have gotten better after I installed the Konis.

Bear in mind that the bouncing doesn't happen when I'm driving. Everything is very tight when I'm moving. I only get the bouncing when I come to a complete stop. As an interesting example, I looked in the driver's side rear view mirror when stopping today. You could actually see the horizon bouncing a couple times as the car moved.

I'm surprised you don't think the bushings would make a difference. Don't the bushings wear out frequently. I'm guessing sloppy bushings would make a sloppy suspension. They could have a spring-like effect if they're worn out.

I always assumed I'd hear the air bag pump when I was driving. I've never heard a thing. I suppose the air bags *could* be leaking. Wouldn't I have problems while driving if the air bags were leaking? I'd expect bouncing all the time.

I think I've got a dealer trip in my future. I'll take the car to the master tech I mentioned. He wasn't happy about the Koni setup but at least he could feel the bouncing. Good thing I have an aftermarket warranty on this car. Heck, maybe I'll call the Car Talk guys tomorrow.
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  #15  
Old 11-10-2007, 09:42 PM
big x big x is offline
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Check the condition of your rear subframe bushes. Unlike the saloon these are hydraulic units and critical for the correct operation of the rear suspension. Over time the rubber cracks and the fluid leaks out resulting in a harsh feeling rear.The subframe itself also moves to much causing vague handling.The first photo shows the new bush.It is much bigger than the saloons and almost the same size as the X5 ones.The bushes date stamp is visible from the side when mounted in the subframe so you can check if they have ever been replaced before.
The airbags seem to have a remarkably consistent life. On my 1999 touring one collapsed at 120k and the other side at 122k. Always replace in pairs !
I find the air pump in the trunk to be almost silent in operation. It charges the 2 reservoirs under the car and when driving should hardly operate at all as long as there are no leaks in the airlines.The ride height is kept constant, the system does not compensate for high speed bumps. All in all my car rides very smoothly and there is no bouncing but it is certainly not a sports car. I have standard rate Bilstiens shocks at the front. The rear dampers should last a very long time.The airbags have there own rebound damping characteristics and the dampers have little work to do.









adam
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  #16  
Old 11-10-2007, 11:33 PM
jj4302 jj4302 is offline
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I'm not going to get technical, but mine doesn't do that either. I'm interested to find out what it is though. Good luck!
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  #17  
Old 11-11-2007, 03:27 PM
tempestv8 tempestv8 is offline
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Quote:
Originally Posted by big x View Post
Check the condition of your rear subframe bushes. Unlike the saloon these are hydraulic units and critical for the correct operation of the rear suspension. Over time the rubber cracks and the fluid leaks out resulting in a harsh feeling rear.The subframe itself also moves to much causing vague handling.



adam

Hi Adam,

How many miles did you have on your Touring before you replaced these bushes?

Thanks,

Lawrance
'03 530i T/auto with 170,000 kms
Melbourne, Australia
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  #18  
Old 11-13-2007, 09:44 AM
big x big x is offline
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I replaced the bushes at 132k. The rear was harsh, thumping over potholes and transverse ridges. I would say they need replacing on average at around 80k/5 year mark if you want to retain good ride quality.

adam
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  #19  
Old 11-13-2007, 02:32 PM
Jase007 Jase007 is offline
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Adam:

Thanks! Those are great pics. Am adding them to my DIY file.


Quote:
find the air pump in the trunk to be almost silent in operation.
I agree but the buffetting [air pressure changes] when car is 1st started from sitting overnight are what I notice.

Quote:
It charges the 2 reservoirs under the car and when driving should hardly operate at all as long as there are no leaks in the airlines.
It is this [bolded / underlined] part that I want to learn form BMW / techs as to what / when the pump operates. Just call me curious.

Unfortunately, www.powerflexusa.com doesn't offer their purple poly bushes in the USA for E39 rear sub-frame. Would be a nice solution to eliminate the fluid-filled prone to failure BMW peices.

Ace:

Quote:
I have the stock sport suspension. The pro-Koni struts/shocks were stock from the factory.
I too have the BMW factory sport suspension [have window sticker from 1st owner] but ... when I pulled things apart ... the ones that were in there sure looked like SACHs / Boge OEM BMW replacements in my hand and ready to install. Do know where there is literature that shows BMW "sport" suspension had pro-konis as dampers? I'm not questioning what you found, rather, looking for a source of data as to exactly what BMW used as a sport suspension on my 528iT. [perhaps pro-konis were usedon 540iT?].

Thanks.
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Last edited by Jase007; 11-13-2007 at 02:37 PM.
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  #20  
Old 11-13-2007, 04:36 PM
big x big x is offline
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Jason, here is the full technical description of the touring air suspension. Every owner should read it !

BTW Sachs are the OE shocks. Easy to tell as they have alloy shock bodies the same color as the suspension arms. BMW are not going to fit Koni when there are two high quality German companies available... Bilstein and Sachs Boge.

REAR SUSPENSION SYSTEMS

The standard rear suspension of the 528i sport wagon follows the design characteristics of
the four link elasto kinematic system of the E38/E39 sedan vehicles.


The main design difference is the separation of the coil springs and dampers.

• The coil springs are positioned between the perches of the wheel carriers and the underside of the rear floor pan.
• The shock absorbers are positioned diagonally between the lower lateral control arm
and the rear axle sub frame.
This configuration provides the wide, uniform load space in the cargo area.

Since the shock absorbers are now mounted directly to the sub
frame, the sport wagon requires unique sub frame hydro mounts.
The hydro mounts contain a fluid that helps to suppress road/suspension noise and vibrations from transmitting into the vehicle
body.

The hydro mounts require new special tools for removal and
replacement. See E39 sport wagon special tools section on page

96.

ELECTRONIC HEIGHT CONTROL (EHC) AIR SUSPENSION SYSTEM
OVERVIEW
The self-leveling air suspension system is being introduced on US market E39 sport wagon
vehicles.
The mechanical design is identical to the standard 528i rear suspension however the coil
springs are replaced by air cushion springs. The air pressure in the air springs is managed by
the EHC system which automatically controls the ride height under all operating conditions.
91

OVERVIEW OF EHC CONTROL SYSTEM

The control philosophy of EHC is to "Initiate a control sequence only when necessary". The
system offers the following advantages:

• The control system operates independently from the vehicle’s engine (no engine driven
hydraulic pump system as per previous self leveling systems).
• Individual control of the rear wheels is possible
• An uneven load is identified and compensated for
• Uneven road surfaces are identified and not compensated for
• Automatic control is interrupted when cornering
• The system is diagnosable using the DIS or MoDiC
The air suspension system consists of the following components:



93
EHC SYSTEM COMPONENTS
CONTROL MODULE
The Control Module is mounted in the module carrier box in the luggage compartment on
the right side. It contains the processing electronics and final stages for operation of the
EHC system.
The control module receives the following
inputs for its processing functions:
• KL 30 & 31 (Power/Ground)
• KL 15
• Left & Right Ride Height Sensors
• K Bus for;
- Vehicle speed
- Engine running
- Door/tailgate - open/closed
The control module incorporates two filters (slow/rapid) for processing the input signals
from the ride height sensors. Depending on the operating mode, either the slow or rapid filter
is used to check the need for a regulating sequence.
The slow filter is used during the normal operation mode to prevent normal suspension travel
from causing the system to make adjustments.
The rapid filter is used during the pre-run and tailgate (LID) modes to ensure that the suspension
is adjusted quickly while the vehicle is being loaded or checked prior to operation.
E39 Features 06
EHC
CONTROL
MODULE

AIR SPRINGS

The air spring is made from a flexible rubber material. It
forms an air tight cavity which provides the calculated
spring rate required for the sport wagon.

As the spring compresses downward the bottom edge of
the rubber material rolls along the vertical surface of the
base mount cylinder.

Air is added or removed from the air spring through its top
port. The top port of each spring is connected to a reservoir and the air supply pipes. The reservoirs are required
to hold additional air due to the compact design of the
springs.

REAR AXLE LEVEL SENSORS


Hall effect sensors are mounted on the left
and right sides of the rear suspension for
ride height detection. They are pivoted by a
coupling rod through the rear axle swing
arms.

The hall sensors produce a varying voltage
input to the control module as the suspension height changes.

If the vehicle is equipped with Xenon headlights the right side sensor contains an
additional sensor for the automatic head

E39 Features 07
light level adjustment system.

WARNING DISPLAYS

If the system is faulted and off-line or set in the transport mode, the following is displayed:

Basic Cluster: A warning lamp indicator is illuminated used on the
basic cluster.


High Cluster: A message is posted in the high cluster matrix display.

94

AIR SUPPLY SYSTEM (LVA)

The air supply system is identified as the LVA in the diagnosis program and in the repair
manual. It is mounted in the spare tire well compartment. The components are housed in
a sound deadening carrier, through rubber bushings, to prevent operating noises from
being transmitted through the vehicle’s interior.

With the exception of the compressor relay, individual replacement parts for the air supply
system are not available. If diagnosis determines a defect in any of the other air system
components, complete replacement is necessary.

The air supply system consists of the following components:

• Compressor assembly with;
- Piston compressor
- Electric motor
- Air dryer (desiccator)
- Pressure relief solenoid valve
- Pressure maintenance valve
- Check valves
• Compressor Relay (Replaceable)
• Solenoid Valve Block (2 - two way
valves)
• Lines - including distributor block
95
E39 Features 05

AIR SUPPLY SYSTEM (LVA) OPERATION

The single stage piston compressor produces a maximum pressure of 13.5 Bar. The compressor is maintenance free - provided it is used in a dust free environment. This includes
the compressor’s intake air filter.

The compressor is driven by a DC motor that is controlled by the compressor relay through
the control module.

When the compressor is activated, the pressure builds up to a working pressure of 11.4
Bar (+0.8/-1.5 Bar). This is controlled through the pressure maintenance valve. The air
under pressure is fed through the dryer and check valve to the solenoid valve block for the
air springs.

There is one solenoid valve in the valve block for each air strut. This allows the system to
compensate for uneven loads in the vehicle and maintain the vehicles ride height at all
times.

Pressure is drained through the left or right solenoid valve (energized open) the pressure
relief solenoid valve, restricter, check valve and dryer back to the inlet side of the compressor pump.


97

EHC SYSTEM OPERATION

A fully functional EHC system is controlled by one of three different modes of operation.
The operation mode is selected by the control module based on current conditions provided by the monitored input signals. The main modes of operation are:

• Pre-Run/Post-Run Mode
• Normal Mode
• Tailgate Mode
Two special operating modes are also included in the control module programming.

• New/replacement mode (pre ZCS encoded). This mode provides basic operation.
• Transport Mode - Transport mode is set at the factory and raises the vehicle 30mm to
prevent vehicle damage during transportation. It must be deactivated with the DIS/
MoDiC prior to customer delivery.
PRE-RUN/POST-RUN MODE

The Pre-Run mode is activated when the vehicle is parked and the control module is in the
sleep mode. Opening a door or the tailgate initiates a system wake up and the control module comes on-line.

The control module performs a self-check of the control electronics and sensors. If no fault
is found, the system will check the ride height and institute a rapid regulation if the height
varies by more than 40mm.



99
NORMAL MODE OPERATION
Once the rear lid is closed, KL 15 switched ON and the engine started, the system switches
into the normal operation mode. In the normal mode, the control module will constantly
monitor the input signals from the ride height sensors and will activate a correction if the
ride height deviates by at least 10mm.
TAILGATE OPERATING MODE
The tailgate operating mode is activated if the gate is opened with KL - 15 On and the
engine running. The difference between this mode and the normal operating mode is the
response time is rapid instead of slow .

SPECIAL OPERATING MODES

• ASSEMBLY LINE MODE (New control module)
The assembly line mode refers to control module manufacturing. New control modules
are stored in a deactivated state. The control programming is not active and must first
be ZCS encoded.

After installing a replacement control module, it must be coded using the DIS or MoDiC.
The instrument cluster fault display will remain illuminated until the control module is
coded.

• TRANSPORT MODE
The vehicle rolls off the factory assembly line with the EHC control module in the transport mode. The transport mode inflates the air springs to a higher position (approx.
30mm higher) than the normal mode in order to avoid damage during transit.

The system will not respond to any inputs that would alter the height of the vehicle. The
fault indicator (base cluster) is illuminated or instrument cluster matrix display (high cluster) provides the message “Leveling System” to draw attention to the transport mode
setting.

The Service Functions section of the diagnosis program is used to activate/deactivate
the transport mode. Once the transport mode is deactivated, check the vehicle Ride
Height Offset making sure the vehicle rear axle height is to specification.

CONTROL INTERRUPTS

CORNERING

To prevent unnecessary suspension adjustments while driving through corners, a “control
interrupt” is built into the system. Above 30MPH the control module monitors the left/right
ride height sensors for a difference of 30mm. Exceeding this difference will put the system
into a control interrupt and no adjustment will take place. The control interrupt last for a
duration of 5 minutes.

VEHICLE LIFTING

The ride height control is interrupted when the vehicle is raised on a lift or with a jack. The
system monitors the ride height sensor inputs and when the height limit of 90 mm is
exceeded, the control is switched OFF until the vehicle is lowered again.


101
EHC SERVICE INFORMATION
DIAGNOSIS/CODING
• The EHC control module is connected to the diagnostic link. The EHC control module
activates the fault display in the instrument cluster to alert the operator of the off-line status
of the system. The EHC control module stores up to three electrical/electronic
faults.
• Diagnosis/troubleshooting of EHC is carried out using the fault symptom troubleshooting
program of the MoDiC or DIS. The EHC system has an extensive diagnosis program.
• Replacement control modules are shipped in the factory mode. The control modules
must be ZCS encoded using the DIS or MoDiC to activate the operating parameters.

102
DIS/MODIC SERVICE FUNCTIONS PROGRAM
The Service Functions program of the DIS/MoDiC provides the Transport Mode activation/
deactivation and Ride Height Offset functions (see next page).
Once the transport mode has been released, or if the system requires left to right side
height adjustment, the ride height "OFFSET" must be carried out to ensure that the vehicles
suspension has a base ride height level starting point.
The "HEIGHT OFFSET" is adjusted using the DIS or MoDiC. The procedure is as follows:
• Place the vehicle on a level surface unloaded.
• Access the Height Offset program in the service function menu.
• Measure the base ride height from the lower edge of the wheel housing to the center of
the wheel hub.
• Check measured height against the specifications listed
• Use the DIS/MoDiC to correct the ride height if the value differs from the listed specification.
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  #21  
Old 11-13-2007, 10:16 PM
aceswerling aceswerling is offline
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Location: Seattle
 
Join Date: May 2006
Posts: 96
Mein Auto: 540iT
Interesting. I hadn't thought of the subframe bushings. That's a great idea. I think my car went over some rough roads before I bought it. I figure anything could have happened to the suspension. I'll have my mechanic take a look.

On a side note, I've heard those poly bushings will make the car ride really rough. The regular rubber bushings appear to be a major weak spot on an e39. Poly bushings appear to be a natural solution as long as the ride doesn't stink. Anybody tried them?

Last edited by aceswerling; 11-13-2007 at 10:18 PM.
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  #22  
Old 11-14-2007, 01:49 AM
Steve Wright Steve Wright is offline
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Location: Berkshire, UK
 
Join Date: Jun 2007
Posts: 136
Mein Auto: BMW e39 M5 Tourer
I replaced the bushes in mine with the saloon ones to allow me to fit the m5 braces back to the centre exhaust. It feels far more solid and no more noisy than the original bushes.
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  #23  
Old 11-14-2007, 09:34 AM
Jase007 Jase007 is offline
Wrenchin' fool ...
Location: nova
 
Join Date: Jun 2004
Posts: 770
Mein Auto: e39 528it
Excellent info Big X! [added to my file]

Aces: Red energy suspensions or similar poly bushes have a different durometer [harder] than Powerflex purple poly bushes [bushings]. Like all things, poly is a compromise. OEM black rubber is too soft but designed for "average" consumer that wants less NVH. Purple Poly blend of PowerFlex is a step up. Generic Red poly next and then Delrin and then ? before solid mounts.

I have been R&R 'ing bushings on Porsche & BMWs for years and there are mountains of info out there for which ones are "good", "to hard", "to soft" etc... All I can add is that for a dd BMW, with Powerflex bushings, the ride was sharper and the increased NVH negligable.
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2000 528iT Sport 5M (mfg. 5/1999) ~ 1990 325iX 5M
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  #24  
Old 11-14-2007, 07:52 PM
big x big x is offline
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Location: UK
 
Join Date: Nov 2007
Posts: 32
Mein Auto: 525 touring
In some markets other than the US and UK I believe the base model touring had standard springs rather than self-levelling airsprings. On a higher mileage car that had pump failure and old airsprings that would be the most economic repair route. The springs are listed in the BMW parts catalogue. As far as I can tell dropping of the rear subframe is required to fit conventional springs. Replacing the airsprings on the other hand is easy, they fit straight in and they are not that expensive.
One important aspect to note is the rear shocks are not attached to the body but to the subframe and are angled at 45 degrees to save space. Clearly there are much higher loads going through the touring subframe than the saloon even when not carrying loads and this accounts for the substantial construction and hydraulic design of the carrier mounts
Note how everything including brake callipers,subframe,suspension arms,subframe,shock bodies and bearing carriers are all alloy to save weight. Add in the cost of the airpump, ride height sensors and relays and it's clear the Touring's rear suspension is one of the most expensive ever made.







adam
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  #25  
Old 11-14-2007, 08:15 PM
big x big x is offline
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Location: UK
 
Join Date: Nov 2007
Posts: 32
Mein Auto: 525 touring
It is possible to observe how much the subframe is moving in motion by sitting in the trunk and looking through the access holes that are directly above the shock tops.
First remove the floor by undoing the screws hidden under the tie down hooks.Then remove the 2 black access covers. The subframe moves around much more than one might imagine from both torque from the diff and road undulations.


adam
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