ASE A1 Engine RepairCylinder Head and Valve TrainMedium
A technician is diagnosing an overhead valve (OHV) engine that exhibits a consistent 'clattering' noise originating from the valve train. The noise is present at all engine speeds but becomes more pronounced when the engine is cold. A visual inspection reveals sufficient oil level. Which of the following is the MOST likely cause?
- AExcessive valve guide wear.
- BA collapsed hydraulic lifter.
- CA worn camshaft lobe.
- DA bent pushrod.
Show answer & explanationAnswer & explanation
Correct answer: B. A collapsed hydraulic lifter.
A collapsed hydraulic lifter is a very common cause of valve train clatter. When a hydraulic lifter fails to pump up with oil, it cannot take up valve lash, leading to excessive clearance and a 'clattering' noise. This noise often is worse when cold because the oil is thicker and takes longer to circulate and fill the lifter, or a faulty lifter struggles more with cold oil.
Why the other options are wrong
- A. Excessive valve guide wear primarily causes oil consumption and blue smoke, not typically a distinct clattering noise from the valve train.
- C. A worn camshaft lobe typically causes a 'ticking' noise due to excessive lash, but a collapsed lifter often produces a more pronounced 'clatter' and is more sensitive to oil temperature.
- D. A bent pushrod would likely cause a severe misfire, a constant loud metallic noise, or valve train damage, not just a clattering that's worse when cold.
Collapsed Hydraulic Lifter
A hydraulic valve lifter that fails to maintain oil pressure within its internal chamber, causing it to 'collapse' and lose its ability to take up valve lash, resulting in excessive clearance and noise.
- Causes a distinct 'clattering' or 'ticking' noise.
- Often worse when the engine is cold or at low oil pressure.
- Leads to reduced valve lift and potential misfires.
Memory trick: Clatter, clatter, lifter's splatter, check the oil, that's the matter.