ASE A1 Engine RepairCylinder Head and Valve TrainHard
A technician is diagnosing an overhead valve (OHV) engine with a persistent ticking noise that increases with engine RPM. The noise is isolated to a specific cylinder. After removing the valve cover, the technician observes that the pushrod on the affected cylinder has excessive vertical play when the valve is closed. Which component is the most likely cause?
- ACollapsed hydraulic lifter
- BBent pushrod
- CWorn rocker arm pivot
- DWorn camshaft lobe
Show answer & explanationAnswer & explanation
Correct answer: A. Collapsed hydraulic lifter
Excessive vertical play in the pushrod on an OHV engine with a ticking noise indicates that the hydraulic lifter is not maintaining its proper length, allowing for excessive valve lash. A collapsed hydraulic lifter cannot pump up and take up this clearance.
Why the other options are wrong
- B. A bent pushrod would typically cause binding or erratic valve movement, not necessarily excessive vertical play when the valve is closed.
- C. A worn rocker arm pivot would cause play in the rocker arm itself, but not necessarily excessive vertical play in the pushrod (unless the pivot wear was extreme enough to drop the rocker arm significantly).
- D. A worn camshaft lobe would result in reduced valve lift and duration, but typically wouldn't cause excessive *vertical* pushrod play when the valve is closed unless the lobe was severely worn down to its base circle, in which case the lifter would still try to maintain zero lash.
Collapsed Hydraulic Lifter
A hydraulic valve lifter that fails to pump up with oil, resulting in excessive valve lash, a ticking noise, and improper valve operation.
- Causes a ticking noise, especially when hot or at startup.
- Results in excessive valve lash and pushrod play.
- Can lead to reduced valve lift.
- Requires replacement when collapsed.
Memory trick: Ticking from the top, check the lifter's flop.