See Figures 1, 2, 3, 4 and 5
Whenever a spongy brake pedal indicates that there is air in the system, or when any part of the hydraulic system has been removed for service, the system must be bled. In addition, if the level in the master cylinder reservoir is allowed to go below the minimum mark for too long a period of time, air may enter the system, necessitating bleeding.
If only one brake caliper or wheel cylinder is removed for servicing, it is usually necessary to bleed only that unit. If, however, the master cylinder, warning valve, or any of the main brake lines are removed, the entire system must be bled. There is a specific sequence you should follow when bleeding the brakes of your Volvo (see drawings).
Be careful not to spill any brake fluid onto the brake surfaces (disc, pads, drum and linings) and, of course, the paint work. When bleeding the entire system, the rear of the car should be raised higher than the front. Only use brake fluid bearing the designation SAE 1703 (SAE 70 R3), or DOT 4. Never reuse old brake fluid.
The following procedure is acceptable for cars with and without ABS.
- Check to make sure that there are not mats or other materials obstructing the travel of the brake pedal. During bleeding, the full pedal travel should be 6 in. (150mm) for the 140, 240, 260 series and later models, and 5.5 in. (140mm) for the 164 and 1800 series (providing that both circuits are bled simultaneously).
- Clean the cap and the top of the master cylinder reservoir, and make sure that the vent hole in the cap is open. Fill the reservoir to the maximum mark. Never allow the level to dip below the minimum mark during bleeding, as this will allow air into the system.
- If only one brake caliper or line was removed, it will usually suffice to bleed only that wheel. Otherwise, prepare to bleed the entire system beginning at the left front wheel.
- Remove the protective cap for the bleeder screw, and fit a 5 / 16 line wrench on the nipple. Install a tight plastic hose onto the nipple, and insert the other end of the hose into a glass bottle containing clean brake fluid. The hose must hang down below the surface of the fluid, or air will be sucked into the system when the brake pedal is released.
- Open the bleeder screw a maximum of 1 / 2 turn. Have a helper slowly depress the brake pedal until it bottoms, pause a second or two, and then quickly release the pedal. This should be repeated until the fluid flowing into the bottle is completely free of air bubbles. During this procedure you should check the master cylinder reservoir frequently and top up the fluid level as needed. Have your helper press the pedal to the bottom of its travel and hold it there while you tighten the bleeder screw. Install the protective cap.
On the 240, 260 series and the 1980 and later models, when bleeding the front brakes, connect bleeder hoses to all three bleeder nipples (two on the 760 GLE), submerge the hoses in brake fluid and open the nipples. Keeping the reservoir full, pump the brake pedal until no bubbles appear, hold the pedal down and close the nipple.
- If the entire system is to be bled, follow the above procedure for the remaining nipples at the right front, left rear and right rear wheel IN THAT ORDER. Generally, it is sufficient to bleed each circuit once. However, if the pedal continues to feel spongy, repeat the bleeding sequence. Remember to keep the master cylinder reservoir level above the minimum mark.
- Fill the reservoir with the specified brake fluid to the maximum mark.
- With the bleeder valves closed and the master cylinder topped off, turn the ignition ON but do not start the engine. Apply moderate force to the brake pedal simulating a hard stop. The pedal must travel no more than 2.4 in. (61mm) without ABS; 2.17 in. (55mm) with ABS. The brake warning light (and ABS light) must stay off. Switch off the ignition and continue to bleed the system until the pedal travel and/or the brake warning light tests are satisfied.
- Top off the reservoir and install the cap. Remember to put the rubber caps onto the bleeder nipples at each caliper.