Brakes - Squeak, Scrape, Or Rattle From Rear Brakes

Mercedes Benz C 250 (204.052) (CANADA) V6-2.5L (272.921) Technical Service Bulletin # LI42-20_P-052990 Date: 120117

Brakes - Squeak, Scrape, Or Rattle From Rear Brakes

Squeaking, scraping or rattling noises from area of rear wheel brake without brake actuation

Topic number LI42.20-P-052990

Version 1

Design group 42.20 Parking brake

Date 01-17-2012

Validity Model 204/207

Reason for change

Complaint:

Squeaking, scraping or rattling noises from area of rear wheel brake without brake actuation.

Attachments

Cause:

1. Brake shoes of the parking brake touch the inside of the brake disk bowl in the axial direction.

The brake shoes of the parking brake are fastened to the cover panel with retaining springs. These retaining springs must be centered on the

elongated holes in the brake shoes. If this is not the case, the affected brake shoe may touch the lip of the brake disk bowl in the axial direction

and cause noises (see attachment 1).

2. Stator clip has slipped and touches the inside of the brake disk bowl in the axial direction.

A stator clip is pushed onto the support for the brake shoes of the parking brake (brake stator). This prevents the brake shoes from working

into the aluminum wheel carrier. If this clip is pushed too far on during assembly, it may be widened in the radius area of the brake stator (see

attachment 2, item 3). This widening means that permanent secure fastening of the stator clip is no longer guaranteed and it may wander from

the brake stator in the axial direction until it touches the lip of the brake disk bowl.

3. Expansion lock has play.

The expansion lock is designed to have sufficient component tolerance to guarantee proper functioning of the parking brake even when

covered with brake dust deposits in the course of operation. This play can cause rattling noises on rough roads.

Remedy:

Re. 1. Brake shoes:

Replacement of the silver-colored brake shoe retaining springs installed as standard for black retaining springs (see parts ordering note).

When installing the retaining springs, the following points must be observed:

Page 19

^Use of installation tool W 112 589 09 61 00 (see attachment 3).

^ Insert the retaining springs through the cutouts in the rear axle shaft flange so that they can be mounted vertically on the brake shoes (see

attachment 4).

^ Center the retaining springs on the elongated holes in the brake shoes (see attachment 5).

^ To hook up the retaining springs in the cover panel, turn them counterclockwise (to the left) to prevent tilting and to avoid stresses.

Re. 2. Stator clip:

Check the stator clip for abrasion marks and correct seating on the brake stator (see attachment 2, item 1: The sides of the stator clip must be

flush with the brake stator). If abrasion marks are visible on the stator clip, or if it is installed incorrectly, the stator clip must be replaced.

Re. 3. Expansion lock:

Install an additional snap clip between the extension spring and the expansion lock as per the installation note (see attachment 6, Figure 1).

When installing, please not:

^ Position the snap clip in the center of the extension spring and make sure that it engages properly in the extension spring (see attachment 6,