2.5L, 4.0L and 4.2L Engines
See Figures 1, 2, 3, 4, 5 and 6
- Remove the engine from the vehicle and mount it on a work stand.
- Drain the oil.
- Remove the flywheel or torque converter, match marking the pieces for installation.
- Remove all drive belts.
- Remove the fan and hub assembly.
- Remove the crankshaft pulley and vibration damper.
- Remove the timing case cover.
- Remove the oil pan.
- Remove the oil pump and pickup.
- Remove the rod bearing caps, marking them for installation.
The main bearing caps are numbered from front to rear and have an arrow to indicate the forward position. The upper main bearing inserts are grooved to provide oil channels while the lower inserts are smooth.
Remove the main bearing caps and lower inserts, marking them for installation as follows:
- Remove the lower insert from the bearing cap.
- Remove the upper insert by loosening all the other bearing caps and inserting a small cotter pin tool in the crankshaft journal oil hole. Bend the cotter pin as illustrated to fabricate the tool.
- With the cotter pin tool in place, rotate the crankshaft so that the upper bearing insert will rotate in the direction of its locking tab.
Because there is no hole in the No. 3 main journal, use a soft-faced tool, such as a tongue depressor, to remove the bearing insert. After withdrawing the insert approximately one inch (25mm), it can be removed by applying pressure under the tab.
- Lift out the crankshaft.
A replacement oil pickup tube must be used. Do not attempt to install the original. Make sure the plastic button is inserted in the bottom of the pickup screen. Always use a new rear main seal. If new bearings are installed, check clearances with Plastigage®.
- Check the crankshaft for wear or damage to the bearing surfaces of the journals. Crankshafts that are damaged can be reconditioned by a professional machine shop.
- Using a dial indicator, check the crankshaft journal run-out. Measure the crankshaft journals with a micrometer to determine the correct size rod and main bearings to be used. Whenever a new or reconditioned crankshaft is installed, new connecting rod bearings and main bearings should be installed.
- Clean all oil passages in the block (and crankshaft if it is being reused).
A new rear main seal should be installed any time the crankshaft is removed or replaced.
- Wipe the oil from the crankshaft journal and the outer and inner surfaces of the bearing shell.
- Place a piece of plastic gauging material in the center of the bearing.
- Use a floor jack or other means to hold the crankshaft against the upper bearing shell. This is necessary to obtain accurate clearance readings when using plastic gauging material.
- Install the bearing cap and bearing. Place engine oil on the cap bolts and install. Torque the bolts to specification.
- Remove the bearing cap and determine the bearing clearance by comparing the width of the flattened plastic gauging material at its widest point with the graduations on the gauging material container. The number within the graduation on the envelope indicates the clearance in millimeters or thousandths of an inch. If the clearance is greater than allowed, REPLACE BOTH BEARING SHELLS AS A SET. Recheck the clearance after replacing the shells.
Main bearing clearances must be corrected by the use of selective upper and lower shells. UNDER NO CIRCUMSTANCES should shims be placed behind the shells to compensate for wear!
- Install new bearing upper halves in the block. If the crankshaft has been turned to resurface the journals, undersized bearing must be used to compensate. Lay the crankshaft in the block.
- Install the lower bearing halves in the caps.
- Use Plastigage® to check bearing fit.
- When the bearings are properly fitted, install and torque the bearing caps.
- Check crankshaft end-play to determine the need for thrust washers.
- While you're at it, it's a good idea to replace the rear main seal at this time.
- Install sufficient oil pan bolts in the block to align with the connecting rod bolts. Use rubber bands between the bolts to position the connecting rods as required. Connecting rod position can be adjusted by increasing the tension on the rubber bands with additional turns around the pan bolts or thread protectors.
- Position the upper half of main bearings in the block and lubricate them with engine oil.
- Position crankshaft keyway in the same position as removed and lower it into block. The connecting rods will follow the crank pins into the correct position as the crankshaft is lowered.
- Lubricate the thrust flanges with clean engine oil or engine rebuilding oil. Install caps with the lower half of the bearings lubricated with engine oil. Lubricate the cap bolts with engine oil and install, but do not tighten.
- With a block of wood, bump the shaft in each direction to align the thrust flanges of the main bearing. After bumping the shaft in each direction, wedge the shaft to the front and hold it while torquing the thrust bearing cap bolts.
In order to prevent the possibility of cylinder block and/or main bearing cap damage, the main bearing caps are to be tapped into their cylinder block cavity using a wood or rubber mallet before the bolts are installed. Do not use attaching bolts to pull the main bearing caps into their seats. Failure to observe this information may damage the cylinder block or a bearing cap.
- Torque all main bearing caps to specification. Check crankshaft end-play, using a flat feeler gauge.
- Remove the connecting rod bolt thread protectors and lubricate the connecting rod bearings with engine oil.
- Install the connecting rod bearing caps in their original position. Torque the nuts to specification.
- Install all parts in reverse order of removal. See related procedures in this section for component installation.