Function of service brake - GF42.10-P-2000GG

MODEL 460, 461.217 /219 /223 /227 /229 /238 /239 /249 /266 /267 /302 /321 /322 /323 /326 /327 /328 /329 /331 /332 /335 /336 /337 /338 /341 /342 /345 /365 /366 /367 /368 /401 /402 /403 /404 /405 /450 /451 /452 /454 /455 /456 /458 /459, 463

Fig 1: Identifying Service Brake Operation Diagram

Courtesy of MERCEDES-BENZ USA

General function

The vehicles are equipped with a hydraulic dual-circuit brake with vacuum assist. The vacuum required for the brake servo in gasoline and diesel engines is generated by the induction pipe vacuum and the vacuum pump, respectively.

A check valve is integrated into the vacuum line at the brake servo in all vehicles.

Disk brakes with 4-piston calipers are used at the front axle and duo servo drum brakes are used at the rear axle.

The brake at the front and rear axle is adjusted automatically.

If the brakes are applied when the vehicle is moving forwards, only the rear brake shoes of the rear axle are adjusted. The driver should therefore apply the brakes forcefully a few times occasionally when reversing to allow the front brake shoes to adjust.

The force applied to the brake pedal is transferred to the dual-circuit master brake cylinder via the piston rod. The dual-circuit master brake cylinder is coupled to the tandem brake unit.

The tandem brake unit increases the pressure applied by the driver to the brake pedal. The increased pressure is transferred to the fixed calipers of the disk brake and to the wheel brake cylinders of the drum brake via the brake lines.

The brake pads of the disk brake are applied to the brake disk by the piston of the fixed calipers; the brake shoes are applied to the drum brake by the piston of the wheel brake cylinder.

If the vacuum is no longer present, the system continues to function as a normal hydraulic braking system. The driver must then apply more force to the brake pedal.

Brake circuit splitting

Brake circuit 1 acts on both fixed calipers, each with 4 pistons, at the front axle

Brake circuit 2 acts on the two wheel brake cylinders at the rear axle.

If one brake circuit fails the vehicle is only braked at one axle.

	Function of brake vacuum system		GF43.10-P-3001GG
	Function of brake hydraulic system		GF42.10-P-3002GG
	Design / function of rear wheel brake		GF42.10-P-3104GG
	Task / function of rear axle automatic adjuster		GF42.10-P-3105GG