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Carlisle TechTips Automatic Adjuster Maintenance

Carlisle Brake & Friction automatic adjusters are used for in-line adjustment of wet brakes and Hi-Torque brakes. The adjuster functions to provide brake running clearance at each brake application. In addition to adjusting for lining wear, the adjuster also compensates for clearance reduction due to contraction of the drum. Sufficient clearance is set to avoid brake drag under most conditions.

Operation
The fluid connection to the brake is made from the top of the adjuster.

With the brake in the "Off” position, back pressure on the brake side of the adjuster – produced by the brake shoe return springs – keeps the floating piston assembly in the position shown in (1). The sensing piston spring keeps the fluid passageway sealed.

Initial brake application pressure moves the floating piston assembly to the position shown in (2), forcing sufficient fluid into the brake to take up brake clearance. This movement takes place at a pressure level below that required to open the fluid passageway.

Application pressure build-up causes the fluid passageway to be opened as seen in (3). Through this passage flows additional fluid as needed to compensate for lining wear; it also provides an "open" line to maintain brake pressure when the brake is on.

When brake pressure is released, the fluid passageway closes before the floating piston assembly starts to move – as in (2). The floating piston is forced back to its seat by the brake shoe return springs which provides the desired lining-to­drum clearance, as in (1).

In the event of normal drum expansion and subsequent cooling, the lining-to-drum clearance is reduced. Upon the next application less fluid is required to bring the shoes in contact with the drum. The adjuster, therefore, would assume a position as shown in (4). As brake application pressure is increased, the fluid passageway opens as shown in (5). The floating piston spring then forces the floating piston to the position shown in (3). Upon release of pressure the adjuster returns to the position shown in (1) ... readjusting the lining clearance to normal from the contracted drum position.

Pressure and Fluid
All adjusters are limited to 700 PSI maximum pressure. Rubber parts are compatible with petroleum (mineral oil) base fluids.

View Adjuster Diagrams

Maintenance
Visually inspect adjuster cap or adjuster base and housing for leakage. Check fittings and joints for leaks and looseness and tighten if necessary. Check adjuster mounting bolts for looseness and retighten if necessary.
 
Overhaul
Use only CARLISLE approved parts.

1. Remove adjuster from vehicle by disconnecting fluid lines and removing mounting bolts. Plug fluid ports and clean outside of adjuster.
2. Remove housing from cap or adjuster base carefully to prevent piston assembly (3 or 4) from falling out of housing.
3. Inspect internal parts of adjuster for damage and replace as needed.                                     

NOTE: Check piston assembly by inserting a smooth blunt tool into the small hole in face of piston, and pushing inward. If there is no movement, replace with a new piston assembly. If there is definite movement, use mouth to blow into small hole. If air passes through the assembly, replace with a new part. (The Internal sensing piston can be depressed only about 1/16", and should require 20-40 lbs. force to depress it).

Coat threads of housing with Never-seez®  and reassemble adjuster in reverse sequence of                disassembly.