300D (123.133) L5-3.0L DSL Turbo (617.952) (1984)
Brake Master Cylinder: Technical Service Bulletins
Brake Master Cylinder - Update/Bleeding/Testing
TO:
OUR MERCEDES-BENZ PASSENGER CAR DEALERS
DATE:
October, 1983 REF. NO. 42/82
SUBJECT:
A. NEW BRAKE MASTER CYLINDER MODELS 107 AND 126
B.
SPONGY BRAKE PEDAL - ALL MODELS
C.
UNNECESSARY REPLACEMENT OF BRAKE MASTER CYLINDERS - ALL MODELS
A.
New Brake Master Cylinder - AH Models
Since July 1983 a new master cylinder has been installed in vehicles with doublediaphragm brake booster. The new master cylinder has a 1" diameter
primary piston for the front brake circuit (formerly 15/16"). The rear brake circuit secondary piston diameter of 3/4" remains unchanged.
Production Phase-In
Model
Chassis
Chassis End Number
380 SL
107.045
028726
380 SE/SEL
126.032/033
048642
500 SE/SEL
126.036/037
036886
380 SEC
126.043
007912
500 SEC
126.044
007818
300 SD
126.120
050790
Parts Information
Part Name
Part Number
Brake Master Cylinder
004 430 26 01
B.
Spongy Brake Pedal - All Models
Insufficient bleeding of the brake system may be the cause of customer complaints of spongy brake pedals. In this case, thorough bleeding, according to
Operation No. 42- 010, is necessary (see Service Microfiche).
When using a bleeding unit, it is essential to step down fully on the brake pedal several times while bleeding the brakes.
If the spongy brake pedal condition persists, complete bleeding might be necessary a second time. Contact your Field Service Manager for further
information on this subject.
C.
Unnecessary Replacement of Brake Master Cylinders - All Models
Recent tests of brake master cylinders, returned under warranty, have proven that most of the units are functioning properly.
If complaints related to the brake master cylinder occur, the following test should be performed before any part is replaced:
1.
With the engine turned off, actuate brake pedal several times to exhaust vacuum in the brake booster completely.
2.
Depress brake pedal by applying a moderate pedal pressure. Maintain force for approximately one (1) minute. The brake pedal travel must not
change during this time.
NOTE:
With the engine running, the brake pedal will go down further as vacuum builds up. This may create the false impression that the brake pedal
travel is excessive.