How are crankshaft end play and bearing clearance checked during overhaul?

How are crankshaft end play and bearing clearance checked during overhaul?

• A. Use a dial indicator for end play and plastigauge or micrometers to verify main and rod bearing clearances per spec.
• B. Spin the crankshaft and listen for noises.
• C. Check end play with a feeler gauge by hand.
• D. Measure crankshaft diameter with a caliper only.

Answer: (A)

Crankshaft end play and bearing clearance are measured to ensure the engine parts move and fit within the manufacturer’s tolerances under operating load. End play is the axial movement of the crankshaft in the main bearings, while bearing clearance is the radial gap between each journal and its bearing. Using a dial indicator to check end play provides a direct, quantified reading of how much the crank can move along its axis when you apply a push and pull. This gives the exact value to compare against the spec. For bearing clearance, plastigauge is the standard direct method: lay a small piece on the journal, install the bearing cap and torque to spec, then remove the cap and measure the width of the flattened plastigauge. The width correlates to the actual clearance, which you compare to the engine’s specifications. Micrometers can help verify related dimensions (like journal diameter and bearing thickness), but plastigauge gives a straightforward clearance measurement under the cap’s clamped condition. Spinning the crank and listening for noises only hints at problems but doesn’t quantify tolerances. Checking end play by hand with a feeler gauge is not precise enough for the required axial and radial tolerances. Measuring crank diameter with a caliper alone won’t reveal the true bearing clearance once the cap is torqued. That’s why the combination of a dial indicator for end play and plastigauge (or equivalent precise clearance measurement) is the best practice.

Crankshaft end play and bearing clearance are measured to ensure the engine parts move and fit within the manufacturer’s tolerances under operating load. End play is the axial movement of the crankshaft in the main bearings, while bearing clearance is the radial gap between each journal and its bearing.

Using a dial indicator to check end play provides a direct, quantified reading of how much the crank can move along its axis when you apply a push and pull. This gives the exact value to compare against the spec. For bearing clearance, plastigauge is the standard direct method: lay a small piece on the journal, install the bearing cap and torque to spec, then remove the cap and measure the width of the flattened plastigauge. The width correlates to the actual clearance, which you compare to the engine’s specifications. Micrometers can help verify related dimensions (like journal diameter and bearing thickness), but plastigauge gives a straightforward clearance measurement under the cap’s clamped condition.

Spinning the crank and listening for noises only hints at problems but doesn’t quantify tolerances. Checking end play by hand with a feeler gauge is not precise enough for the required axial and radial tolerances. Measuring crank diameter with a caliper alone won’t reveal the true bearing clearance once the cap is torqued. That’s why the combination of a dial indicator for end play and plastigauge (or equivalent precise clearance measurement) is the best practice.