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JOB SHEET 139
Inspecting and Measuring the Crankshaft, Main Bearings, and Saddle Bores Name:
Station:
Date:
NATEF Correlation This Job Sheet addresses the following NATEF task(s): 1.C.7
1.C.8
Inspect crankshaft for end play, straightness, journal damage, keyway damage, thrust flange and sealing surface condition, and visual surface cracks; check oil passage condition; measure journal wear; check crankshaft sensor reluctor ring (where applicable); determine necessary action. (P-2) Inspect main and connecting rod bearings for damage and wear; determine necessary action. (P-2)
Performance Objective(s) Upon completion of this Job Sheet, you will be able to properly inspect and measure the crankshaft.
Tools and Materials Service manual Dial indicator Plastigauge® Outside micrometer Feeler gauge set Straight edge Torque wrench
Protective Clothing/Equipment Goggles or safety glasses with side shields Describe the vehicle being worked on: Year
With the crankshaft still installed, measure the end play by placing a dial indicator on the end of the crankshaft and use a prybar to move the crankshaft back and forth. What is your reading and what is the specification? End Play Measured
End Play Specification
2.
Check if there are any identifying marks placed on the main bearing caps. Describe any marks you see.
3.
If there are no identifying marks, use a hammer and number-punch set to label them. Task Completed
4.
Draw the bolt removal sequence for the crankshaft below.
5.
Remove the crankshaft by following the manufacturer’s service procedure. Note: Make
sure to keep the main bearings in order. A bent crankshaft may be indicated when one bearing wears more than the others. Task Completed
The greatest amount of wear occurs on the middle bearings
Axis of bent crankshaft Axis of crankshaft Figure 53.34 Crankshaft misalignment. Main bearing wear caused by a bent crankshaft or a misaligned crankcase.
After removing the crankshaft, visually inspect it in the following places.
Area
Visual Description
Main journal surface Connecting rod journal surface Keyway Woodruff key Thrust flange Oil passages Crankshaft sensor ring 7.
Place the crankshaft on a set of vee blocks. Using the dial indicator, check each main journal for out of round by measuring on both sides of the journal and reporting the maximum.
Main Journal #
Maximum Out-Of-Round
1 2 3 4
5 8.
Are any of your measurements outside of the manufacturer’s specifications?
9.
Describe the wear patterns on the crankshaft main bearings. Do the wear patterns match any visual marks on the crankshaft?
With the crankshaft still resting on the vee blocks, use the outside micrometer to measure vertical taper and horizontal taper. Report only the maximum taper for each journal.
Main Journal #
Maximum Taper
1 2 3 4 5
Connecting Rod Journal #
Maximum Taper
1 2 3 4
5 A vs. B = vertical taper C vs. D = horizontal taper A vs. C and B vs. D = out-of-round Check for out-of-round at the end of each journal
A C
B D
Figure 53.39 Crankshaft journal measurements. 11.
There are a few different methods of checking for crankshaft cracks. List one method that could be used to check your crankshaft for cracks.
12.
Place the crankshaft to the side for now. Stand the crankshaft on end to prevent warping. Task Completed
13.
What is the manufacturer’s specification for the maximum amount of saddle bore misalignment?
Using a straightedge and feeler gauge, measure each of the block’s main journals and report the maximum amount of misalignment.
Figure 53.6 Checking main bearing bore alignment.
Centerline of warped crankcase
True centerline of crankcase Figure 53.7 The crankcase can be warped. (Courtesy of Dana Corporation) 15.
Based on your measurements from this Job Sheet, what services (if any) would you recommend for the engine block and crankshaft?
16.
Reinstall the old main bearings and the crankshaft. Place a strip of Plastigauge® on each of the main journals of the crankshaft. Task Completed Place plastigage full width of journal about 1/4" off-center
Check width of plastigage 0.002" clearance
321.51
Installing plastigage
321.51
321.5 1
Measuring plastigage
Figure 53.43 Checking bearing oil clearance with plastigage.
Torque the main bearing caps to the correct specification and use the correct tightening sequence. Task Completed
18.
Now, remove the crankshaft main bearing caps using the removal sequence and check the Plastigauge® on each of the journals. Record the oil bearing clearances in the chart below.
Main Journal #
Oil Bearing Clearance
1 2 3 4
5 19.
Are the oil bearing clearance measurements more than the specification?
20.
What service/machining procedures need to be taken if the oil bearing clearance measurements were out of specification?
21.
Based on your measurements, does this engine need different sized be arings?
INSTRUCTOR EVALUATION 4 3 2 1 0
Mastered Task Able to Perform Task Independently; Some Additional Training Suggested Able to Perform Task with Close Supervision; Requires Additional Training Unable to Perform Task Not Attempted
