BRAKE GP-PARKING 1227197 - Caterpillar

Series EnginesErrors can result in valve clearance checking or adjusting because of oil in the top of the push rod where the valve adjustment screw rides. This error could be as much as 0.10 mm (.004").
Make note of the following information in the Valve Clearance Checking Procedures in the Testing Modules of the Service Manuals for 3500 Series Engines.
Before checking or adjusting the valve clearance, push down on the adjusting screw to force the oil out of the top end of the push rod. This can be done by using a socket and an extension, (as a lever) on the adjustment screw locknut to force the adjustment screw down into the push rod.