ASE A1 Engine RepairEngine Block AssemblyMedium
A technician is preparing to install a new crankshaft. What is the MOST critical step to ensure proper crankshaft main bearing alignment and prevent premature wear?
- AChecking the crankshaft for straightness before installation.
- BMeasuring crankshaft end play after installation.
- CTorquing main bearing caps to manufacturer specifications in the correct sequence.
- DApplying a generous amount of assembly lube to the journals.
Show answer & explanationAnswer & explanation
Correct answer: C. Torquing main bearing caps to manufacturer specifications in the correct sequence.
Properly torquing main bearing caps to manufacturer specifications in the correct sequence is critical because it ensures the bearing bores are round and aligned, providing the correct crush and clearance for the bearings, which directly impacts crankshaft alignment and prevents premature wear.
Why the other options are wrong
- A. Checking straightness is important, but even a straight crank will wear prematurely if the bearing caps are improperly torqued.
- B. Measuring end play confirms thrust bearing function, but doesn't ensure main bearing alignment.
- D. Assembly lube is important for initial startup, but doesn't ensure alignment.
Main Bearing Cap Torque
The precise force applied to the fasteners securing the main bearing caps to the engine block. Correct torque ensures the bearing bores maintain their specified roundness and alignment.
- Critical for achieving correct bearing crush and clearance.
- Incorrect torque leads to distorted bores, premature bearing wear, and potential engine failure.
- Must follow manufacturer's specified torque values and sequence (e.g., specific order, multiple steps, angle torque).
Memory trick: Torque is king for bearings true, alignment depends on what you do.