ASE A1 Engine RepairCylinder Head and Valve TrainMedium
A technician is diagnosing an engine with a persistent 'clatter' or 'tapping' noise originating from the valve train, which increases with engine speed. After removing the valve cover, they observe excessive clearance between a rocker arm and the valve stem tip on one cylinder. Which of the following is the MOST likely cause?
- AA weak valve spring
- BA collapsed hydraulic lifter
- CA worn valve guide
- DAn improperly adjusted solid lifter
Show answer & explanationAnswer & explanation
Correct answer: D. An improperly adjusted solid lifter
Excessive clearance between the rocker arm and valve stem tip in an engine with solid lifters directly indicates an improper lash adjustment. This condition would cause a noticeable tapping noise as the components make contact.
Why the other options are wrong
- A. A weak valve spring would reduce clamping force but not directly cause excessive clearance between the rocker arm and valve stem tip, though it could lead to valve float at high RPMs.
- B. A collapsed hydraulic lifter would typically cause excessive clearance, but the question specifies 'solid lifter' in the context of adjustment.
- C. Worn valve guides primarily lead to oil consumption and valve wobble, not directly to excessive rocker arm-to-valve stem clearance.
Solid Lifter Adjustment
Solid lifters require precise valve lash adjustment to ensure proper valve operation and prevent excessive noise or valve damage.
- Requires periodic adjustment
- Too much clearance causes tapping noise
- Too little clearance can hold valve open
Memory trick: Listen, Locate, Lash: The three L's of valve noise.