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| Crankshaft Diagnosis |
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A crankshaft will make a clunking noise or a sharp knock if the clearance
between the bearing and the crankshaft journal is excessive. Excessive
crankshaft end play will cause a series a problems including flywheel or torque
converter damage, belt misalignment, and a leaking rear main seal just to
mention a few.
When removing a crankshaft its important to mark the bearing caps for re
installation. Crankshaft end play is measured with a dial indicator mounted on
the engine and the indicator on the crankshaft flange. Use a pry bar or a large
screwdriver to move the crankshaft back and forth. Its important to check the
specifications and clearance should be minimal a few thousandths at the most.
An outside micrometer is used to check for crankshaft journal wear. Check both
around and along the journals for taper and out of round. Journals can wear at
the ends or in the middle. Check for roundness at least two different points, they
usually wear a one place (TDC).
When replacing the bearings make sure the oil holes in the block line up with
holes in the bearing. If the block or journal have been machined it may require
over sized bearings. Always check the clearances with plastigage. Insert the
plastigage in the center of the bearing and then properly torque the cap.
Measure the thickness with the gauge on the package for specifications and
note an uneven thickness indicates taper.
In summary if there is a sharp rapping noise especially at idle its probably the
crankshaft and it should be checked for crankshaft end play. In most cases this
can be achieved by mounting a dial indicator on the timing cover and the tip of
the gauge on the harmonic balancer.
between the bearing and the crankshaft journal is excessive. Excessive
crankshaft end play will cause a series a problems including flywheel or torque
converter damage, belt misalignment, and a leaking rear main seal just to
mention a few.
When removing a crankshaft its important to mark the bearing caps for re
installation. Crankshaft end play is measured with a dial indicator mounted on
the engine and the indicator on the crankshaft flange. Use a pry bar or a large
screwdriver to move the crankshaft back and forth. Its important to check the
specifications and clearance should be minimal a few thousandths at the most.
An outside micrometer is used to check for crankshaft journal wear. Check both
around and along the journals for taper and out of round. Journals can wear at
the ends or in the middle. Check for roundness at least two different points, they
usually wear a one place (TDC).
When replacing the bearings make sure the oil holes in the block line up with
holes in the bearing. If the block or journal have been machined it may require
over sized bearings. Always check the clearances with plastigage. Insert the
plastigage in the center of the bearing and then properly torque the cap.
Measure the thickness with the gauge on the package for specifications and
note an uneven thickness indicates taper.
In summary if there is a sharp rapping noise especially at idle its probably the
crankshaft and it should be checked for crankshaft end play. In most cases this
can be achieved by mounting a dial indicator on the timing cover and the tip of
the gauge on the harmonic balancer.