Master Cylinder: Description

WARNING: This page is about a different car, the 2006 Dodge Magnum, 2006 Dodge Charger, and 2006 Chrysler 300. However, it is still accessible from the selected car via links, so may be relevant.

There are two different master cylinder designs used depending on whether the vehicle is an early build vehicle or a later build vehicle. To simplify the differentiation between early and later brake systems, for this service information they are referred to as the MK25 master cylinder and the MK25E master cylinder. This is because the master cylinders change when the availability of the antilock brake systems change. Early build vehicles use MK25 ABS and later build vehicles use MK25E ABS. Be aware that these type master cylinders are also used on vehicles that are not equipped with antilock brakes.

Fig 1: PRIMARY AND SECONDARY PORTS - MK25E

Courtesy of DAIMLERCHRYSLER CORP.

Although similar in function and appearance, the MK25E master cylinder does not have a pressure switch located on the bottom and it has larger outlet ports with SAE flares. The primary port (1) is designed for 5/16 inch (8 mm) tubing and the secondary port (2) is designed for 1/4 inch (6.25 mm) tubing.

Both standard MK25 and MK25E master cylinders have 25.4 mm bores. Although appearing and serviced the same, the master cylinder used on SRT8 and Police vehicles has a larger 27 mm bore. The SRT8 and Police Package master cylinder can be identified by a green dot placed on the body of the master cylinder.

Fig 2: BRAKE PRESSURE SWITCH - SRT8

Courtesy of DAIMLERCHRYSLER CORP.

On SRT8 vehicles with the MK25 ABS system, the brake pressure sensor (3) which normally mounts to the bottom of the master cylinder is mounted to the primary brake tube (3) near the master cylinder (1).