ASE A1 Engine RepairEngine Block AssemblyHard
A technician observes excessive oil consumption and blue smoke from the exhaust on an engine with high mileage. Upon disassembly, the cylinder walls show significant taper and out-of-roundness. Which of the following is the MOST appropriate next step for the engine block?
- AInstall new standard size piston rings and reassemble.
- BReplace the entire engine block with a new or remanufactured unit.
- CRebore the cylinders to an oversize, then install new oversize pistons and rings.
- DHone the cylinders to remove glaze and install new rings.
Show answer & explanationAnswer & explanation
Correct answer: C. Rebore the cylinders to an oversize, then install new oversize pistons and rings.
Significant taper and out-of-roundness indicate that the cylinder walls are worn beyond what honing can correct. Rebore the cylinders to an oversize, then install new oversize pistons and rings is necessary to restore proper cylinder geometry, piston-to-cylinder clearance, and ring sealing, which will resolve excessive oil consumption.
Why the other options are wrong
- A. Installing new rings on worn, tapered cylinders will not solve the sealing issue and oil consumption.
- B. Replacing the entire block is a last resort, usually for cracked blocks. Reboring is a standard and less costly repair for worn bores.
- D. Honing only removes glaze and very minor imperfections; it cannot correct significant taper or out-of-roundness.
Cylinder Reboring
A machining process that enlarges a worn cylinder bore to a specific oversize diameter, restoring its roundness and straightness. This requires matching oversize pistons and rings.
- Corrects significant taper, out-of-roundness, and scoring.
- Removes worn material and creates a new, perfectly cylindrical surface.
- Always necessitates installing oversize pistons and rings to maintain correct piston-to-cylinder clearance.
Memory trick: Too much wear, bore it anew, with bigger pistons, the engine's true.