Measuring With Plastigage
CRANKSHAFT MAIN BEARING CLEARANCEEngine crankshaft bearing clearances can be determined by use of Plastigage, or equivalent.The following is the recommended procedure for the use of Plastigage:
1. Remove oil film from surface to be checked. Plastigage is soluble in oil.
2. The total clearance of the main bearings can be determined only by removing the weight of the crankshaft. This can be accomplished by either of two methods:
1mMETHOD-1 (PREFERRED)
Shim the bearings adjacent to the bearing to be checked. This will remove the clearance between upper bearing shell and the crankshaft. Place a minimum of 0.254 mm (0.010 inch) shim between the bearing shell and the adjacent bearing cap. Tighten the bolts to 18 Nm (13 ft. lbs.) torque.
^ CHECK NO. 1 BEARING: Shim No. 2 main bearing.
^ CHECK NO. 2 BEARING: Shim No. 1 and No. 3 main bearing.
^ CHECK NO. 3 BEARING: Shim No. 2 and No. 4 main bearing.
^ CHECK NO. 4 BEARING: Shim No. 3 main bearing (3.9L). Shim No. 3 and No. 5 main bearing (5.2L and 5.9L).
^ CHECK NO.5 BEARING: Shim No. 4 main bearing (5.2L and 5.9L).
NOTE: Remove all shims before assembling engine.
METHOD-2 (ALTERNATIVE)
Support the weight of the crankshaft with a jack placed under the counterweight adjacent to the bearing being checked.
Placement Of Plastigage In Bearing Shell:
1. Place a piece of Plastigage across the entire width of the bearing cap shell. Position the Plastigage approximately 6.35 mm (1/4 inch) off center and away from the oil holes. In addition, suspect areas can be checked by placing the Plastigage in that area. Tighten the bearing cap bolts of the bearing being checked to 115 Nm (85 ft. lbs.) torque. DO NOT rotate the crankshaft or the Plastigage may be smeared, giving inaccurate results.
Clearance Measurement:
2. Remove the bearing cap and compare the width of the flattened Plastigage with the scale provided on the package. Plastigage generally comes in two scales (one scale is in inches and the other is a metric scale). Locate the band closest to the same width. This band shows the amount of clearance. Differences in readings between the ends indicate the amount of taper present. Record all readings taken. Refer to Engine Specifications.
3. Plastigage is available in a variety of clearance ranges. The 0.025-0.076 mm (0.001-0.003 inch) range is usually the most appropriate for checking engine bearing clearances.
CONNECTING ROD BEARING CLEARANCE
Engine connecting rod bearing clearances can be determined by use of Plastigage, or equivalent. The following is the recommended procedure for the use of Plastigage:
1. Remove oil film from surface to be checked. Plastigage is soluble in oil.
2. Place a piece of Plastigage across the entire width of the bearing cap shell. Position the Plastigage approximately 6.35 mm (1/4 inch) off center and away from the oil holes. In addition, suspect areas can be checked by placing the Plastigage in the suspect area.
3. The crankshaft must be rotated until the connecting rod to be checked starts moving toward the top of the engine. Only then should the rod cap, with Plastigage in place, be assembled. Tighten the rod cap nut to 61 Nm (45 ft. lbs.) torque. DO NOT rotate the crankshaft or the Plastigage may be smeared, giving inaccurate results.
4. Remove the bearing cap and compare the width of the flattened Plastigage with the scale provided on the package. Plastigage generally comes in two scales (one scale is in inches and the other is a metric scale). Locate the band closest to the same width. This band shows the amount of clearance. Differences in readings between the ends indicate the amount of taper present. Record all readings taken. Refer to Engine Specifications.
5. Plastigage is available in a variety of clearance ranges. The 0.025-0.076 mm, (0.001-0.003 inch) range is usually the most appropriate for checking engine bearing clearances.