Bleeding the hydraulic system (Skoda Felicia)

Warning! Hydraulic fluid is a highly toxic substance - try to avoid getting it on exposed skin and in the eyes. Wash off any accidental splashes immediately with plenty of clean water. Remember that even a small amount of brake fluid entering the digestive tract can have the most serious consequences, including death. Some types of hydraulic fluids are also flammable and can ignite upon contact with surfaces heated to a sufficiently high temperature - observe appropriate fire safety measures. Along with toxicity, brake fluid is highly chemically aggressive and can easily damage the paintwork of car body panels. If the fluid gets on body elements, wash off any traces immediately with plenty of water. Finally, the reader should pay attention to the high hygroscopicity of brake fluid. The latter means the ability to absorb moisture from the air, which means that it is unacceptable to use the fluid that has been stored for a long time in a non-hermetically sealed container. Add only fresh hydraulic fluid of the required grade to the system.

On models equipped with ABS, before disconnecting the hydraulic brake lines, it is imperative to disconnect the battery. The battery should be connected only after all hydraulic lines of the brake tract have been connected. Violation of this requirement is fraught with air entering the hydraulic modulator, the removal of which during the normal bleeding of the system is not possible and requires the use of a special electronic tester (VAG 1552).

General information

The correct functioning of any hydraulic system can only be achieved by completely removing air locks from its tract. Air is removed from the brake system by "bleeding" it.

When bleeding the brake system, add only fresh hydraulic fluid of the required grade. Fluid drained from the system cannot be reused. Before starting the procedure, make sure that there is a sufficient supply of fresh brake fluid.

If there is the slightest suspicion of the presence of low-quality brake fluid in the system, the hydraulic circuit must be thoroughly flushed with fresh fluid of the required grade. In addition, it is necessary to replace all the cuffs and sealing rings used in the components and lines of the system.

If hydraulic fluid is lost or air enters the system as a result of leaks, all existing defects must be eliminated before bleeding.

Drive the car onto a ramp/inspection pit, turn off the engine, set the parking brake and engage first or reverse gear, then support the rear wheels with wedges. Alternatively, the car can be jacked up and placed on reliable supports (to make access easier, remove the wheels).

Check the tightness of the fittings of the brake lines and the caliper/wheel cylinder bleeder valves. Thoroughly wipe the outside of the valves and the surrounding surfaces.

Remove the cap and add fresh hydraulic fluid to the master cylinder reservoir, bringing its level to the MAX mark. Loosely screw the cap back on. Remember that during the bleeding of the system, the fluid level in the reservoir should not fall below the MIN mark, otherwise air may get into the cylinder and all efforts will go down the drain.



Nowadays, special kits are always available in car accessory stores that allow one person to bleed the car's brake system. Using this type of kit greatly simplifies the bleeding procedure and reduces the risk of sucking back the hydraulic fluid and air that have already been pumped out of it. If you do not have a special kit at hand, you should seek the help of an assistant. The procedures for bleeding the brake system by one or two people are described below in the relevant subsections.

When bleeding the hydraulic circuit using a special kit, the vehicle must be prepared for the procedure in accordance with the instructions given above. Then follow the instructions included with the kit. The general principle of using such kits is described below in the relevant subsections.

Regardless of which bleeding method is chosen, the sequence of the procedure must remain unchanged, which is the key to complete removal of air from the hydraulic tract.

Sequence of pumping execution

1. If the system is bled to remove air that has entered the circuit as a result of disconnecting components of only one part of the hydraulic circuit, it will be sufficient to bleed only that specific brake mechanism.

2. If it is necessary to remove air locks from the entire system, the bleeding sequence should be as follows:

• a) Right rear wheel brake mechanism;
• b) Left rear wheel brake mechanism;
• c) Right front wheel brake mechanism;
• d) Left front wheel brake mechanism.

Basic method for bleeding the brake system with two people

1. Prepare a suitable drain container with transparent walls, a piece of plastic tube or rubber hose that fits tightly onto the bleed valve, and a spanner to turn the valve. Get a friend to help you.



2. Remove the dust cap from the bleed valve of the corresponding brake mechanism, put the head of the open-end wrench on the valve, then pull the hose, the other end of which should be lowered into a transparent container partially filled with clean brake fluid. The cut of the hose should be completely immersed in the liquid.

3. Make sure that the fluid level in the master cylinder reservoir is sufficient. Remember that during the entire procedure the fluid level should not fall below the MIN mark.

4. Ask an assistant to press the foot brake pedal all the way down a few times to create pressure in the system. On the last stroke, the pedal should be fixed in the lower position.

5. While holding the foot brake pedal depressed, unscrew (about one turn) the bleed valve and watch the fluid containing air bubbles being released through the hose into the drain container. The assistant should continuously press the pedal until it rests on the floor. When the fluid stops flowing out of the hose, tighten the bleed valve and ask the assistant to slowly release the pedal. Immediately check the fluid level in the master cylinder reservoir and make adjustments if necessary.

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6. Repeat the procedures in paragraphs 4 and 5 until clear, bubble-free fluid starts to come out of the hose. If the first brake mechanism in the system is bled after the master cylinder has been emptied, the pause between cycles should be at least five seconds, which is necessary for the internal cavities of the cylinder to be filled with fluid.



7. Once bleeding is complete, tighten the valve securely, remove the hose and spanner from it, and install the dust cap.

Note: Do not tighten the valve too tightly.

8. If necessary, repeat the procedure, bleeding the brake mechanisms of the remaining wheels of the vehicle in the required order in order to completely remove air from the hydraulic tract.

Procedure for bleeding the brake system using a one-way valve kit

1. As the name of the kit suggests, its main component is a one-way valve mounted in the drain pipe and ensuring its one-way flow. The transparent drain container should be installed in such a way that it can be easily seen from the driver's seat in the car.



2. The drain tube is placed on one end of the bleeding valve, which is left open for the entire duration of the procedure. Then the operator sits in the driver's seat and begins to press and release the foot brake pedal with smooth, even movements until transparent brake fluid, free of air bubbles, begins to come out of the tube.

3. Do not forget about the need to maintain the fluid level in the master cylinder reservoir.

Procedure for bleeding the brake system using a kit with a compressed air source

1. A spare tire of a car is usually used as an independent source of compressed air, the pressure in which should be reduced slightly below normal (see kit manufacturers instructions).



2. By connecting a container filled with hydraulic fluid and connected to a compressed air source to the brake master cylinder reservoir, the operator is freed from the need to manipulate the foot brake pedal. Now it is enough to simply open and close the valve, observing the fluid being displaced from the system.

3. The method is good because having a sufficient supply of hydraulic fluid in a container connected to the master cylinder reservoir allows you not to worry about the need to monitor its level.

4. This method is especially effective when bleeding low-traffic areas, as well as when replacing brake fluid during routine vehicle maintenance.

All methods

1. Once the system has been bled and the normal firmness of the foot brake pedal has been restored, check that the bleed valves are securely tightened, wipe away any spilled fluid with a rag, and make sure that you have not forgotten to put the dust caps on the valves.

2. Check the hydraulic fluid level in the master cylinder reservoir and make the appropriate adjustments if necessary.

5. Hydraulic fluid drained from the system cannot be reused and must be taken to a special collection point for the disposal of toxic waste.

4. Make sure that the foot brake pedal functions properly. If the soft feeling remains when pressing the pedal, then not all the air has been removed from the system and the bleeding procedure should be repeated. If it is not possible to remove air from the tract during repeated bleeding, check the condition of the master cylinder sealing cuffs.

Note: If there is the slightest doubt about the correct functioning of the brake system on models equipped with ABS, the car should be taken to a service station without delay to perform diagnostics of the hydraulic modulator condition using a special VAG 1552 tester.