Notes On Externally Invisible Brake Fluid Loss - AH42.10-P-9406-02A

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Model 117, 118, 129, 140, 156, 163, 164, 166, 167, 168, 169, 170, 171, 172, 176, 177, 190, 197, 202, 203, 204, 205, 206, 207, 208, 209, 210, 212, 213, 215, 216, 217, 218, 220, 221, 222, 223, 230, 231, 238, 242, 243, 245, 246, 247, 251, 253, 257, 290, 292, 293, 297, 414, 415, 420, 447, 448, 452.3/4, 460, 461, 463, 470, 471, 636, 639, 900, 906, 907, 909, 910

Model 211, 219

with ADAPTIVE BRAKE (ABR)

In the case of brake fluid loss which is not visible, it should be checked whether brake fluid has entered the brake booster through a leaking secondary seal in the master brake cylinder. The master brake cylinder must be removed for the test.

Model 452.3/4

There must be no brake fluid in the brake booster.

Otherwise the brake booster must be replaced.

On models 129, 140 to May 94 with acceleration slip regulation (ASR) the connections of the pressure reservoir and the charging pump in the left front wheel well should be checked for leaks. As from June 94 the charging pump is no longer applicable for ASR V.

On model 129 with engine 119, 120 up to June 98 and models 140 and 210 with engine 119 and Electronic Stability Program (ESP), the connections of the charging pump and charging piston unit in the left front wheel well should be checked for leaks.

Model 117, 118, 129, 140, 156, 163, 164, 166, 167, 168, 169, 170, 171, 172, 176, 177, 190, 197, 202, 203, 204, 205, 206, 207, 208, 209, 210, 212, 213, 215, 216, 217, 218, 220, 221, 222, 223, 230, 231, 238, 242, 245, 246, 247, 251, 253, 257, 290, 292, 293, 414, 415, 420, 447, 448, 460, 461, 463, 470, 471, 636, 639, 900, 906, 907, 909, 910

Model 211, 219

with ADAPTIVE BRAKE (ABR)

If there is more than 100 cmi³ of brake fluid in the brake booster, the brake booster must be replaced.

The power diaphragm in the brake booster is resistant to brake fluid, but not the reaction disk and the poppet valve in the master control unit.

Extract brake fluid only when brake booster is installed. With a quantity of up to 100 cm³ , no brake fluid can get to the reaction disk or poppet valve when the brake booster is installed.