When adjusting the slave piston clearance on a compression release brake, which step is correct?

When adjusting the slave piston clearance on a compression release brake, which step is correct?

• A. After the intake and exhaust valves are adjusted.
• B. Before the intake and exhaust valves are adjusted.
• C. After setting lash between valve bridges and valve stems.
• D. Before starting the engine.

Answer: (A)

The key idea is getting the valve train geometry settled before setting the clearance of the compression release slave piston. The slave piston operates in concert with the valve gear, so its proper clearance depends on the exact positions the valves will hold once they’re adjusted. If you set the slave piston clearance first, any subsequent valve adjustments can change the pushrod and rocker positions and throw the clearance off, leading to improper engagement or binding of the release mechanism. By performing valve adjustments first and then establishing the slave piston clearance to the specified spec, you ensure the release mechanism engages correctly for the actual valve geometry. Do this with the engine off, and proceed with valve adjustments before touching the slave piston clearance.

The key idea is getting the valve train geometry settled before setting the clearance of the compression release slave piston. The slave piston operates in concert with the valve gear, so its proper clearance depends on the exact positions the valves will hold once they’re adjusted. If you set the slave piston clearance first, any subsequent valve adjustments can change the pushrod and rocker positions and throw the clearance off, leading to improper engagement or binding of the release mechanism. By performing valve adjustments first and then establishing the slave piston clearance to the specified spec, you ensure the release mechanism engages correctly for the actual valve geometry. Do this with the engine off, and proceed with valve adjustments before touching the slave piston clearance.