ASE A1 Engine RepairCylinder Head and Valve TrainMedium
A technician is inspecting a cylinder head that has been removed from an engine. They notice that the valve guides show significant wear, allowing excessive side-to-side movement of the valve stems. This condition is most likely to lead to which of the following engine problems?
- AIncreased oil consumption and premature valve seat wear.
- BReduced oil consumption.
- CImproved valve sealing.
- DIncreased likelihood of valve spring surge.
Show answer & explanationAnswer & explanation
Correct answer: A. Increased oil consumption and premature valve seat wear.
Excessive valve guide wear allows oil to be drawn past the valve stem seals into the combustion chamber, increasing oil consumption. It also causes the valve to seat improperly, leading to accelerated wear on the valve seat and face.
Why the other options are wrong
- B. Excessive valve guide wear would increase, not reduce, oil consumption due to oil bypassing the valve stem seals.
- C. Poor valve guiding leads to improper valve seating, which reduces valve sealing effectiveness.
- D. Valve spring surge is primarily related to valve spring design, RPM, and resonant frequencies, not directly caused by valve guide wear.
Valve Guide Wear
The deterioration of the bore that supports and guides the valve stem, leading to excessive clearance between the valve stem and guide.
- Causes oil to bypass valve stem seals.
- Leads to improper valve seating.
- Increases oil consumption and accelerates valve seat wear.
Memory trick: Wobbly valve, oily exhaust, worn-out seat.