Volkswagen Golf/Jetta 2 manual

Hydraulic system - bleeding
Braking system / Hydraulic system - bleeding

Caution: Take great care not to spill brake fluid onto paintwork as it will act as a paint stripper. If spilled, wash it off at once with cold water.

1 Bleeding of the hydraulic system will be required after any component in the system has been disturbed or any part of the system УbrokenФ. When an operation has only affected one circuit of the system, then bleeding will normally only be required to that circuit (front and rear diagonally opposite).

2 If the master cylinder or pressure regulating valve have been disturbed, then the complete system must be bled. Note that where a brake pressure regulator is fitted, the regulator lever should be pressed toward the rear axle during the bleeding of the rear brakes.

3 One of three methods can be used to bleed the system.

Two-man method
4 Obtain a clean jar and length of tube which will fit the bleed valve tightly. The help of an assistant will be required.

5 Clean around the bleed valve on the rear brake and attach the bleed tube to the valve (see illustration)

12.5 Connect bleed tube to bleed valve
12.5 Connect bleed tube to bleed valve

6 Check that the master cylinder reservoir is topped up and then destroy the vacuum in the brake servo (where fitted) by giving several applications of the brake foot pedal.

7 Immerse the open end of the bleed tube in the jar, which should contain 50 to 76 mm depth of hydraulic fluid. The jar should be positioned about 300 mm above the bleed valve to prevent any possibility of air entering the system down the threads of the bleed valve when it is slackened.

8 Open the bleed valve half a turn and have your assistant depress the brake pedal slowly to the floor and then quickly remove his foot to allow the pedal to return unimpeded.

Tighten the bleed valve at the end of each downstroke to prevent expelled air and fluid being drawn back into the system.

9 Observe the submerged end of the tube in the jar. When air bubbles cease to appear, fully tighten the bleed valve when the pedal is being held down by your assistant 10 Top-up the fluid reservoir. It must be kept topped up throughout the bleeding operations. If the connecting holes in the master cylinder are exposed at any time due to low fluid level, then air will be drawn into the system and work will have to start all over again.

11 Repeat the operation on the diagonally opposite front brake.

12 On completion, remove the bleed tube.

Discard the fluid which has been bled from the system unless it is required for bleed jar purposes. Never use it for filling the system.

With one-way valve
13 There are a number of one-man brake bleeding kits currently available from motor accessory shops. It is recommended that one of these kits should be used whenever possible as they greatly simplify the bleeding operation and also reduce risk of expelled air or fluid being drawn back into the system.

14 Connect the outlet tube of the bleeder device to the bleed valve and then open the valve half a turn. Depress the brake pedal to the floor and slowly release it. The one-way valve in the device will prevent expelled air from returning to the system at the completion of each stroke. Repeat this operation until clean hydraulic fluid, free from air bubbles, can be seen coming through the tube. Tighten the bleed screw and remove the tube.

15 Repeat the procedure on the on the diagonally opposite brake whilst remembering to keep the master cylinder reservoir full.

With pressure bleeding kits 16 These are available from motor accessory shops and are usually operated by air pressure from the spare tyre.

17 By connecting a pressurised container to the master cylinder fluid reservoir, bleeding is then carried out by simply opening each bleed valve in turn and allowing the fluid to run out until no air bubbles are visible in the fluid being expelled.

18 Using this system, the large reserve of fluid provides a safeguard against air being drawn into the master cylinder during the bleeding operations.

19 This method is particularly effective when bleeding УdifficultФ systems or when bleeding the entire system at routine fluid renewal.

All methods
20 If the entire system is being bled, the procedures described above should now be repeated at each wheel. The correct sequence is as follows. Do not forget to recheck the fluid level in the master cylinder at regular intervals and top-up as necessary.

Right-hand rear wheel
Left-hand rear wheel
Right-hand front wheel
Left-hand front wheel
21 When completed, recheck the fluid level in the master cylinder, top-up if necessary and refit the cap. Check the feel of the brake pedal which should be firm and free from any sponginess which would indicate air still present in the system.

22 Discard any expelled hydraulic fluid as it is likely to be contaminated with moisture, air and dirt, which makes it unsuitable for further use.

23 On completion, refit the rubber protector caps over each bleed valve (see illustration).

12.23 Fit bleed valve the protector cap
12.23 Fit bleed valve the protector cap

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