2006 BMW 750Li
Problem for BMW 2006 750Li

1994 740 IL TRACTION CONTROL UNIT, ASC+T




By jim_lundmark on Mar 30, 2009

" "
I REPLACED THIS UNIT BECAUSE IT STARTED LEAKING ON THE POWER STEERING SIDE. I'M ON MY SECOND USED UNIT, HAVEN'T USED THE CAR YET. SEEM TO HAVE AN OVERPRESSURE ISSUE. PRESSURE LINE RUPTURED, REPLACED IT. STILL LEAKS AT BOTH ENDS. FLUID LEAKING OUT OF HYD UNIT. THERE ARE TWO LINES THAT CONNECT TO THE BOTTOM OF THE UNIT THAT HAVE THE SAME FITTINGS. NOT SURE IF I GOT THEM MIXED UP. NEED TO CONFIRM IF THE LINE THAT GOES TO THE RESERVOIR IS CLOSEST TO THE FENDER WELL. IF THIS IS CORRECT, I DO NOT KNOW WHY THIS IS SEEING SO MUCH PRESSURE. ANY ADVICE IS APPRECIATED.

J LUNDMARK
Comments:

Mar 31, 2009

- ---------- there are three lines that connect to the bottom of this unit, all on the power steering steering side. Two have the same fitting and the third is smaller. Of the other two that have the same fitting, one goes to the reservoir and the other i think is the pressure from the pump. the line to the reservoir is closet to the fender wheel well.two short hose couplers, located under the brake booster. had to tear out the booster to get to them to fixed.


Is this your comment? looks like something I wrote. Can you tell me if the line to the the reservoir is the closet to the fender well so I can confirm it is connected correctly. As far as this unit working: I did confirm that the unit I installed has the same part number as the unit I removed. As far as reprograming this system, the Bentley book is misleading because it says nothing about having to do this. Also , I still do not know why I have this overpressure issue. I can't even run the engine for a minute without fluid leaking from the pressure line and the hyd unit. Please advise.

Mar 31, 2009

- please read my post. I need to know which lines connect where to the bottom of the traction control unit. I may have switched them. If I can find this out and they are ok, I still have overpressure issues from the pump to the hyd unit. If I have them crossed, I can switch them and see if it make a difference. I would like to know from someone who can confirm the location of these lines before I arbitrarily do it and possibly damage something. does anyone have a technical diagram that shows this? please advise.

Mar 31, 2009

- I cannot open the diagram you posted.

Mar 31, 2009

- I have this diagram from BMW parts and is not as detailed as to specific connections. Is there a diagram of the hyd unit that indicates which lines connect where on the underside? please advise

Apr 01, 2009

- I am trying to locate detail information on how the traction control unit is connected from the bottom. No one seems to be able to know or have access to this information. Does anyone know how the traction control unit works internally? One of the port connections feeds two solenoids that regulate fluid to two plungers that are connected to the brake system. The bleeder is also tied into this port. Does anyone know if the bleeder is on the pressure side of the unit? The previous answer I received said this system has to be reset by computer. Can that be done without the car running? Because if the car has to run, it's not going to work for me because of this high pressure issue. It's hard to believe
there is no relief valve in this system. If the solenoids are bad are they closed. Are these solenoids normally open or normally closed. Is there a way to check these solenoids. Are they 12/13 volt? Please advise.

Apr 01, 2009

- I HAVE THE EXACT PART NUMBER AS ORIGINAL, I HAVE A TANDEM PUMP. WHY I AM HAVING HIGH PRESSURE ISSUES I DON'T KNOW. TWO LINES THAT CONNECT TO THE BOTTOM OF THE UNIT HAVE THE SAME FITTING. THEY MAY BE SWITCHED BUT I DON'T THINK SO. I NEED A GOOD DIAGRAM OF WHICH LINE FEEDS WHICH PORT TO CONFIRM THIS. ONE LINE IS THE PRESSURE LINE AND THE THE OTHER LINE GOES TO THE RESERVOIR. IF I HAVE THEM CORRECT, I STILL DO NOT KNOW WHY THE PRESSURE IS SO HIGH. I CAN'T RUN THE ENGINE FOR 30 SECS WITHOUT THE MECHANICAL CONNECTIONS LEAKING. I ALREADY RUPTURED ONE HOSE. IT SEEMS THER IS NO PRESSURE RELIEF ON THIS SYSTEM. IF THIS HAS TO BE REPROGRAMMED BY COMPUTER AS YOU SUGGEST, DOES THE CAR HAVE TO RUN TO DO THAT? PLEASE ADVISE

Solution #1

posted on Mar 30, 2009
Not Rated)

livetech

Rank: Wiz 
Rating: 84%, 150 votes
The traction control unit control the rear ride height, this is how the to systems are connected. If the traction control unit that you replaced is not correct for a ride height car, the car won't level out, it has the correct part or the correct program and coding, simple disconnecting the computer will not reset the programming it has to connected to a computer and the info down loaded to traction control unit. There is no bleeding involved other than starting the engine and making sure the powersteering fluid level is correct for the ride height. The programming and encoding will need to be done at a dealer or repair shop that has purchased the software and computer system to do this. to know whether the unit you have bought is correct
you will have to at check out the old part number on the original unit and compare to your. If not take the part number off of the unit that is on there now and check it at the dealer. If you replaced the metal hard component and the black computer you will need to get both part numbers.The pressure for the self leveling system comes from the power steering pump, follow the lines from the rear shocks(leveler) forward you will find it so be a small diameter hose to feed the rear levelers. The levelers are computer controlled you should see a connector for each one after close inspection near the top if I remember correctly. The asc module just monitors ride height and operates the valves in the levelers, weather there is pressurized fluid there .
---------- there are three lines that connect to the bottom of this unit, all on the power steering steering side. Two have the same fitting and the third is smaller. Of the other two that have the same fitting, one goes to the reservoir and the other i think is the pressure from the pump. the line to the reservoir is closet to the fender wheel well.two short hose couplers, located under the brake booster. had to tear out the booster to get to them to fixed.
Comments:

Mar 30, 2009

- What is traction, and what does traction control do on my car while I drive? Traction is the grip that your car’s tires have on the road, which is needed to accelerate, turn and brake. If your car, or more specifically, your tires have little or no grip; your car will not accelerate, turn or brake and will skid. Traction control devices in the car will help prevent this loss of grip so your tires will have traction to accelerate, turn and brake.
The most common and well-known traction control device is the Anti-Lock Brake System (ABS). ABS is designed to prevent your wheels from locking up during panic or hard braking. When braking, if your front wheels lock-up, steering control is lost and your car will continue in the same path as before you attempted to brake. The system consists of a host of speed sensors and a central computer. Speed sensors are located at the wheels of the car, which tell the computer how fast they are turning. The computer constantly evaluates the speed of the vehicle and the speed of the wheels. When the brake pedal is depressed and the speed of the wheel reaches or get close to locking-up, the ABS computer will then modulate the amount of brake pressure (or “pump” the brakes), as fast as fifteen times per second, on that wheel. This continuing modulation or pumping will prevent or correct wheel lock-up and allow the driver to brake and steer. ABS systems do vary from auto manufacturer to auto manufacturer. It is important know if the car you are driving is equipped with ABS and how to brake if ABS is activated. Shortly after its introduction in the marketplace, there were insurance industry studies that showed ABS equipped cars were in a higher rate of accidents then those not equipped. In this study, it was shown that the most frequent factor in these accidents was driver error. Drivers were not putting enough pressure on the brake, not holding brake pressure long enough or trying to pump the brakes. Evidence also suggests that drivers were over confident when driving an ABS equipped car and were not allowing for a safe following or braking distance.
To correctly use the brakes in an ABS equipped car in a panic situation, the driver must apply the brakes 100 percent, using all available force. The ABS computer will prevent brake lockup and the tires sliding on the travel surface. This will allow the driver to steer around the threat. It is important to remember that ABS can increase straight-line stopping distances beyond that of threshold braking in a non-ABS equipped car. ABS offers drivers, in an emergency situation, the ability to maintain steering control so they can steer clear of an obstacle or threat. Current ABS systems give feedback to the driver to let them know it is activated and operating during the current braking maneuver. The most common way that ABS communicates to the driver is a pulsing sensation felt in the braking foot or a rattling noise during braking. This is normal operation and is telling the driver ABS is working. As discussed above, do not attempt to modulate the brake yourself and remember to use all the brake force available. The ABS system will take care of the modulation for you and allow you to steer around a threat.
As marketed by most automakers, but related to ABS, is Traction Control. Traction Control is used to prevent the drive wheels from losing grip when accelerating. Spinning tires during hard acceleration may be dramatic, but it is the slowest way to get to your desired speed. Using the car’s ABS speed sensors at the wheels, the Traction Control computer compares the drive wheel’s speed to the car’s road speed. If there is a loss of grip event during acceleration, there are a number of ways that the Traction Control slows the drive wheels so they can regain grip. The most common method is to use the braking system. When the drive wheels lose grip, the ABS computer can apply the brake to the wheel that has lost grip to slow it down so it can regain grip. Another method for slowing the slipping wheels is to reduce the amount of power applied to them. The computer will electronically modify the amount of fuel entering the engine and/or use the transmission to slow the drive wheels so they can regain grip.
The latest traction control technology introduced to motor vehicles is Stability Control. While ABS and Traction Control help manage the grip of the tires for braking and accelerating, Stability Control helps prevent a car from sliding sideways. Using the same components in the ABS and Traction Control systems, Stability Control adds other sensors. These include; steering wheel angle sensor and yaw rate sensor. Yaw is defined as, "the movement of an object turning on its vertical axis”. Stability Control is used to
manage the amount of understeer a vehicle will exhibit if the driver used too much steering or entering a turn too fast. It will also manage oversteer if the driver uses too much or too little throttle while turning. Much like the other technologies of traction control, Stability Control will apply the brakes and/or throttle to a wheel or a number of wheels, independently, so the driver can regain control.
How does Stability Control help to regain control of the car? The foundation of ABS and Traction Control were already in place when Bosch pioneered Stability Control with their Electronic Stability Program (ESP) in the Mercedes Benz E Class in 1995.
These same technologies were used to correct an impending slide. Reviewing back, ABS can control individual wheels’ braking forces and Traction Control controls individual wheels’ acceleration forces. Stability Control can use either braking or throttle application to correct a slide. To get a better understanding how braking and acceleration forces affect a cars attitude, we must understand the effect of weight transfer during braking, turning and accelerating. To illustrate, we will use a brake and turn exercise to show how weight transfer will allow the driver to steer more effectively around an obstacle. As we know from previous exercises, to turn more effectively, braking should be done prior to turning. During braking, weight is transferred to the front, “loading up” the front wheels. To take these visuals further; imagine a car with a rod or a pole installed vertically through the roof to the ground of the car. Yaw would be the movement or rotation of the car around this rod. Similar forces are applied to a vehicle when turning. Depending on speed and how much steering is applied, the car can understeer or oversteer.
A realistic scenario would be driving down the interstate at typical highway speeds in the center lane. Imagine what you would do if the truck in front of you accidentally drops its load of gravel on the roadway in front of you. A common evasive maneuver would be to steer around the obstacle, going left then right to avoid the gravel. For this given example, you may put too much steering input when turning left and cause the car to understeer. To correct the understeer, the Stability Control could apply the brake to the inside front wheel. In this case, during the left turn, the inside front wheel would be the left front wheel. This braking of the left front wheel causes the car to get back to the driver’s intended path by reducing the amount of understeer. The deceleration of the vehicle causes weight transfer and puts more weight over the steered wheels. During this evasive maneuver, you are only half done and have not steered back into your lane. When making a quick left/right turn, weight transfer can be quite dramatic and the car can deviate from your intended path. When initially turning left, the weight transferred to the right side of the vehicle. When turning back right and getting back into your lane, the weight will unload from the right side of the car and will quickly transfer to the left. This weight transfer will immediately unload the rear tires and can cause the car to oversteer or fishtail. A common method to prevent oversteer in this scenario, thinking back to the car spinning on the rod, would be to slow the inside rear tire. Slowing down the right rear tire will slow or prevent the rotating of the vehicle on its vertical axis

Mar 30, 2009

- Modern vehicles, that offer traction control devices, perform a self-test on the ABS, Traction Control and Stability Control computer(s). If there is an error encountered in any of these systems when starting or while driving, an error light will steadily illuminate in the instrument cluster of the vehicle. During this time, one or more of these traction control devices will be unavailable and you should know how to maintain vehicle control if these aids are unavailable. It is also possible that a vehicle make and model may offer switches which power off the ABS, Traction Control or Stability Control. Please familiarize yourself with the vehicle’s controls and owner’s manual. In a later article, we will cover situations where a traction control technology should be switched off.
Remember, these technological advances only aid the driver and cannot defy the laws of physics. As an example, if you are trying to drive 50mph around a corner that your car can negotiate at 30mph, you will go off the road, no matter how many traction control devices your vehicle is equipped with.

Mar 30, 2009

- http://www.fordwindstarrecall.info/
click the link the brand and model is different but the system is same

Solution #2

posted on Apr 01, 2009
Not Rated)

arjuun

Rank: Guru 
Rating: 86%, 429 votes
SOLUTIONS :
1.If I remember correctly the traction control computer does control the ride level system. The real question did you get the correct trac. control unit as not all 740's came with rear ride leveling. Also the traction control(abs) needs to be programmed and encoded to your specific vehicle as your car has more than the basic options. As for the powersteering the pump also provides pressure for the ride leveling if you don't have powersteering then more than likely the rear won't lift but not completely out of the question as it is a seperate pump section attached to the regular p/s pump.

2.The traction control unit control the rear ride height, this is how the to systems are connected. If the traction control unit that you replaced is not correct for a ride height car, the car won't level out, it has the correct part or the correct program and coding, simple disconnecting the computer will not reset the programming it has to connected to a computer and the info down loaded to traction control unit. There is no bleeding involved other than starting the engine and making sure the powersteering fluid level is correct for the ride height. The programming and encoding will need to be done at a dealer or repair shop that has purchased the software and computer system to do this.
3.The pressure for the self leveling system comes from the power steering pump, follow the lines from the rear shocks(leveler) forward you will find it so be a small diameter hose to feed the rear levelers. The levelers are computer controlled you should see a connector for each one after close inspection near the top if I remember correctly. The asc module just monitors ride height and operates the valves in the levelers, weather there is pressurized fluid there or not is another question.
I hope this solves your problem. If so, Kindly accept my solution.
Regards, Arjun.
Comments:

Apr 01, 2009

- Hydrolic Unit : Removing and installing

Solution #3

posted on Apr 01, 2009
Somewhat Helpful)

carsandcomps

Rank: Guru 
Rating: 89%, 62 votes
Hello Mr. jim_lundmark,

Since it is still leaking with the way you have the lines hooked up, I would try switching them just to see what will happen. It's already leaking, so maybe the two are switched. Worse case scenerio, it will still leak again. I would switch them, and if they still leak, switch them back. If you have a book on the vehicle, maybe it will tell you. I hope this is helpful to you. If you have any further questions please post them, or utilize the Live Chat Option, or use the Repair Service Directory to locate a Service Station near you, or the Premium Assistance. Thank you for posting your question, and again, i hope I have been of some assistance to you. My apologies for not having a definite fix for this.

Solution #4

posted on Mar 31, 2009
Somewhat Helpful)

rajak2009

Rank: Wiz 
Rating: 84%, 238 votes
Sir,

Click this link for more info.
Thanks Good Luck
Appreciate to rate as "Fixya"



Solution #5

posted on Mar 31, 2009
Somewhat Helpful)

final answer

Rank: Wiz 
Rating: 80%, 56 votes

check out this diagram for your car unit.
keep update.rate the solution if helped.
thank you for using fixya.

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