To start with, the changing of the brake fluid using suitable workshop equipment should be described. In picture 1, the essential preparations are shown. A part of this, is suctioning up the the old fluid out of the divided reservoir. The replacement amount can be held smaller, because less mixing takes place. The change over from old to new brake fluid can later be seen more distinctly.

The lid with the level sensor is then replaced by one from the bleeding device. Should this have a tube connection, pressure from above can can be applied to the system. Should there be two connections, a pulsation is even possible, which opens the still possibly closed valves in the control block of the ABS/ESP. In the picture, it can be seen just how important a fender cover is. It prevents e.g., the tubing from coming into contact with the paintwork.

Picture 1 also shows the receptacle with the inflowing new filling. In this case, to exclude the possibility of incompatibility, the same DOT-number should be used. Thereby, the manufacturers information or the description label on the reservoir of the vehicle is important. Caution must always be taken when the basic colour of the fluid differs. Thus, DOT 5 and DOT 5.1 may, under no circumstances, be mixed with each other. The receptacle with the new brake fluid on the workshop device is to be carefully sealed against the humidity in the air.

If the pressure from above is correct and sufficient fluid is present, the vehicle can be raised. Picture 2 shows the receptacle, which is connected, one after the other, to the bleeding screws of the individual brake cylinders. One must not necessarily (according to ATE) begin with the longest distance from the main brake cylinder. What is important, is the use of a small ring spanner for the (particularly older) bleeding screws. These should also not be opened too wide, otherwise the brake fluid will run down on the outside of the tube.

What a blessing it is, that the tubes are transparent. When, on all four wheels a change in the cloudiness stops, one knows that new brake fluid is in the system. Don't forget to top up occasionally. Now you can dismantle the equipment, however, the amount in the reservoir must be brought to the correct level. The more the brake-pads are worn down, the further the level should be from the maximum mark.

There is also the possibility, that one person builds up the pressure using the brake pedal and the another person opens the bleed valves, one after the other. Indeed, this method has one distinct disadvantage. In the open system, the gaiters of the main brake cylinder come into contact with areas where they have never been before. Thereby, leaking could occur. Regardless of which method you use, after pouring in the fluid, wait about 5 to 10 minutes, until the small gas bubbles, caused by the pouring, have disappeared. 07/09