BAR 8Y3898 - Caterpillar

Probable Causes
Valve Lash Setting
Incorrect valve lash settingRocker Arms
Worn rocker armsValve Springs
Worn valve springs or broken valve springsCamshaft
Worn camshaftCylinder Head
Valve seat wearTroubleshooting Sequence
Note: Perform the following procedures in the order that is provided.
Valve Lash Setting
Check the engine valve lash. If necessary, adjust the engine valve lash. Refer to Systems Operation/Testing and Adjusting for information that is related to adjusting the engine valve lash.
If the valve lash can not be adjusted to specifications, proceed to the next Test Step.
If the valve lash is adjusted to specifications, return the unit to service.
Rocker Arms
Inspect rocker arms for pitting or spalling on the roller.
Replace parts, if necessary. If the symptom remains, proceed to the next Test Step.
If the problem has been corrected, return the unit to service.
Valve Springs
Check for cracked valve springs or broken valve springs.
Replace parts, if necessary. If the symptom remains, proceed to the next Test Step.
If the problem has been corrected, return the unit to service.
Camshaft Note: Remove the camshaft in order to inspect the camshaft.
Inspect the camshaft for large grooves.
Measure the camshaft in order to determine if the wear for the camshaft is within specifications. Refer to Reuse and Salvage Guidelines for the correct measurements.
Replace parts, if necessary. If the symptom remains, proceed to the next Test Step. Note: If you replace the camshaft, you must also replace the valve lifters.
If the problem has been corrected, return the unit to service.
Cylinder Head
Remove the cylinder head. Refer to the Reuse and Salvage Guidelines for the specifications that are related to the reusability of the cylinder head and cylinder head components.
Inspect the piston and valve for damage.
Inspect the valve seat for wear.
Replace parts, if necessary.