This is part 3, and the final installment, of our used and abused 2004 Toyota Tacoma Pickup that needed a proper rear drum brake inspection. Continuing on from last week where we were able to get the drum off to check for any shiny wear marks. The bottom anchor for the brake system shown is actually a wedge shaped block. It is covered by a plate shown in this image. The purpose of the wedge which is indicated by the white lines is to force the bottom of the shoes to move down and outward when the wheel cylinder moves the top out and the drum rotates. If the linings are worn on the upper half/third it’s an indication that the linings are frozen on the bottom mounting wedge. This is a mandatory lubrication point during lining replacement service.
Always check a drum brake wheel cylinder for leakage or seepage. They should be dry. On an external dust boot type of cylinder, such as the one shown, pull the boot from its seal groove area and see if there is any evidence of leakage that hasn’t yet leaked outside the sealed off dust boot area.
Brake shoes have mounting pad contact areas, usually 3 pads. They are equally space along the shoe radius. The top mounting pad in indicated by the screwdriver end in this photo.
The middle shoe contact pad is indicated by the screwdriver end in this photo.
The bottom shoe contact pad is indicated by the screwdriver end in this photo.
These shoe contact pad areas should be lubricated when new shoes are installed and should remain lubricated throughout the life of the linings. As shown here, the lubrication is gone and rust has taken its place. In the near future the lining movement during brake application will be hindered by the restriction or lack of free movement of the brake shoe during braking.
This Tacoma has a rear ride/load height proportioning valve. This valve, which is frame mounted, is connected to the axle by the linkage shown.
The frame mounted valve is where the actual pressure adjustment takes place when the vehicle is loaded.
The linkage must be attached, must be free to move under varying loads and must move the adjustment portion of the valve itself. Grasp the linkage, as shown, and attempt to move it and the valves’ adjustment arm. If they don’t move, something is stuck which will stop the pressure from being changed depending on the vehicles load. At that time you don’t know if the valve is stuck wide open, closed or somewhere in between. Valve and linkage replacement is the solution.
The next segments for Tech Tricks Tuesday that we will cover will continue on with the front brake inspection and other areas of brake inspection. Once all of the brake inspection areas are covered the service and repair sequence will be shown. These areas will cover all service areas found during the inspection and will include an ABS light on condition along with a red brake warning light on situation. You can also follow us on Social Media to know more of what we are up to and to get even more tips and tricks.