Teves AST+T (Mark IV G)

INTRODUCTION
The familiar Teves Mark IV ABS and ASC+T systems of the E36 have been modified for the 1995 model year. The new designation is Mark IV G. The "G" stands for the German word "Geschlossen", meaning "closed".
The reference to "closed" refers to the hydraulic system which is now a closed system similar to the Bosch ASC+T 5 system. The earlier Teves Mark IV systems are "open" systems.
The difference in the two types of systems is how the hydraulic unit transfers brake fluid to and from the master cylinder reservoir.
- The open system transfers brake fluid through a hose which is connected between the hydraulic unit and the side of the brake fluid reservoir.
- The closed system transfers brake fluid directly through the master cylinder.

MASTER CYLINDER





The master cylinder of the new system is redesigned. There are two Central valves in each piston which open when the brake pedal is at its upper most position (not pressed).

The fluid circuits in the hydraulic unit now direct the flow of brake fluid as needed directly through the master cylinder instead of through the return line on the open circuit system.

ASC+T OPERATION





ASC+T regulation only occurs if the brake pedal is not depressed.
With this condition the pistons in the master cylinder are at their rest positions which push the central valves open.
The open central valves allow brake fluid to flow freely in both directions directly through the master cylinder.

ABS OPERATION





ABS regulation only occurs when the brake pedal is depressed.
This condition closes the central valves which checks the back flow of the brake fluid when the brakes are applied.
When the system is in ABS regulation the hydraulic unit pump pressure overcomes the driver's pedal pressure and pushes the pistons back to the point of opening the central valves.
At this point a small amount of brake fluid is transferred back to the master cylinder which is the cause of the pulsation in the brake pedal during ABS regulation.

DELETION OF BRAKE PEDAL POSITION SENSOR
Since the brake pedal is always at the top of its travel range during regulation the system no longer requires the brake pedal travel sensor. The previous open system needed this sensor to determine the brake pedal position for pump activation to restore the sinking brake pedal position during regulation.


MARK IV G HYDRAULIC UNIT





NOTE: Illustrated example is for ASC+T system.

ABS has a single inlet and outlet valve for the rear brakes only.

CONTROL MODULE
The new Mark IV closed systems have a new 42 pin control module located in the same position as the earlier 55 pin control module.
The control module requires a new 42 pin brake out box adapter cable for the 83 pin breakout box (P/N 90 88 6 345 200).
E36 TEVES ABS/ASC+T (MARK IV G)