Chrysler Full-Size Trucks 1989-1996 Repair Guide

Pistons and Connecting Rods

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REMOVAL



See Figures 1, 2, 3 and 4

Engine In Vehicle
  1. Remove the cylinder head.
  2.  
  3. Remove the timing chain/gears.
  4.  
  5. Remove the oil pan.
  6.  

After removing the connecting rod cap and bearing, place a short length of rubber hose over the rod bolts to prevent cylinder wall and crank journal scoring when removing or installing the piston and rod assembly.

  1. Pistons should be removed following the firing order of the engine from the top of the cylinder block. Turn the crankshaft until the piston to be removed is at the bottom of its stroke.
  2.  


WARNING
Be careful not to nick the crankshaft journals. On V10 engines, DO NOT remove the black coating on the skirt. This is a factory applied dry lubricant.

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Fig. Fig. 1: Place rubber hoses over the connecting rod studs to protect the crankshaft and cylinders



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Fig. Fig. 2: Carefully tap the piston out of the bore using a wooden dowel


  1. Place a cloth on the head of the piston to be removed and, using a ridge cutter (reamer), remove the deposits from the upper end of the cylinder bore.
  2.  



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Fig. Fig. 3: Use a ridge cutter to remove the ridge from the cylinder bore



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Fig. Fig. 4: The ridge caused by cylinder wear gets thicker as mileage increases


WARNING
Never remove more than1/32in. (0.8mm) from the ring travel area when removing the ridges!

  1. Mark all connecting rod bearing caps so that they may be returned to their original locations in the engine. The connecting rod caps are usually marked. The marks must be matched when re-assembling the engine. Mark all pistons so they can be returned to their original cylinders.
  2.  

Engine Out Of Vehicle

GASOLINE ENGINES

See Figures 5 and 6

On the 5.2L and 5.9L engines, 0.001 in. (0.025mm) undersize journals are indicated by marks on the No. 8 crankshaft counterweight. If the R or M is followed by an X, all those journals are 0.010 in. (0.25mm) undersize. Upper and lower bearing inserts are not interchangeable on any of the V8 engines due to the oil hole and V-groove in the upper bearings. On the 5.2L and 5.9L engine lower bearing halves No. 1, No. 2 and No. 4 are interchangeable; No. 1, No. 2 and No. 4 upper bearing halves are interchangeable, No. 3 bearing is the thrust bearing and No. 5 is the wider rear main bearing. Remove main bearing caps one at a time and check clearance. Check number of cap for proper location.

  1. With the engine removed from the vehicle and placed on a workstand, disconnect the spark plug wires from the spark plugs, and remove the wires and bracket assembly from the attaching stud on the valve cylinder head cover(s), if so equipped. Disconnect the coil to distributor high tension lead at the coil. Disconnect the coil to distributor high tension lead at the coil. Remove the distributor cap and spark plug wires as an assembly. Remove the spark plugs to allow easy rotation of the crankshaft.
  2.  
  3. Remove the fuel pump and oil filter. Slide the water pump by-pass hose clamp (if so equipped) toward the water pump. Remove the alternator and mounting brackets.
  4.  
  5. Remove the crankshaft pulley from the crankshaft vibration damper. Remove the capscrew and washer from the end of the crankshaft. Install a universal puller on the crankshaft vibration damper and remove the damper.
  6.  
  7. Remove the cylinder front cover and crankshaft gear, refer to the cylinder front cover and timing chain procedures in this section.
  8.  
  9. Invert the engine on the workstand. Remove the clutch pressure plate and disc (manual shift transmission). Remove the flywheel and engine rear cover plate. Remove the oil pan and gasket. Remove the oil pump.
  10.  



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Fig. Fig. 5: Be careful to scribe-mark the connecting rods to their caps for correct reassembly

  1. Make sure all bearing caps (main and connecting rod) are scribe-marked so that they can be installed in their original locations. And number each rod and cap with its cylinder number for correct assembly. Turn the crankshaft until the connecting rod from which the cap is being removed is down, and remove the bearing cap. Push the connecting rod and piston assembly up into the cylinder. Repeat this procedure until all the connecting rod bearing caps are removed.
  2.  



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Fig. Fig. 6: Number the rod, cap and cylinder so that the parts will be reassembled in their original positions

  1. Remove the main bearing caps.
  2.  
  3. Carefully lift the crankshaft out of the block so that the thrust bearing surfaces are not damaged. Handle the crankshaft with care to avoid possible damage to the finished surfaces.
  4.  
  5. Remove the rear journal seal from the block and rear main bearing cap.
  6.  
  7. Remove the main bearing inserts from the block and bearing caps.
  8.  
  9. Remove the connecting rod bearing inserts from the connecting rods and caps.
  10.  
  11. If the crankshaft main bearing journals have been refinished to a definite undersize, install the correct undersize bearings. Be sure the bearing inserts and bearing bores are clean. Foreign material under the inserts will distort the bearing and cause a failure.
  12.  

DIESEL ENGINES

For 1994-96 models, the turbocharged intercooler piston has a Ni-Resist insert with a keystone profile for the top compression ring. The new piston has a new design bowl and a 0.275 in. (7mm) longer piston ring than 1989-93 models. These pistons are not interchangeable with the earlier models.

  1. Remove the cylinder head from the block.
  2.  
  3. Remove the oil pan and suction pump.
  4.  
  5. If the cylinder bores have ridges, use a ridge reamer to remove them prior to piston removal. Do NOT remove more metal than is necessary to remove the ridge.
  6.  
  7. If the cylinders have ridges, they are oversize and will need boring.
  8.  
  9. Use a hammer and steel stamp to mark the cylinder number onto each connecting rod cap. Mark the cylinder number onto the top of each piston.
  10.  
  11. Remove the connecting rod bolts and rod caps. Use care so the cylinder bores and connecting rods are not damaged.
  12.  
  13. Use a hammer handle or similar wooden object to push the piston and rod through the cylinder bore.
  14.  
  15. Store the piston/rod assemblies in a suitable rack.
  16.  
  17. If a piston must be replaced, replace with the same part number (grading) that was removed.
  18.  

CLEANING AND INSPECTION



See Figures 7 through 19

This procedure is for the pistons and their cylinder bores. For rod bearings, see the rod bearing replacement procedure.



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Fig. Fig. 7: Take the top measurement 1/2 in. (13mm) below the top.Take the bottom measurement 1/2 in. (13mm) above the top of the piston at BDC

WARNING

Do not use a wire brush or caustic solvent (acids, etc.) on pistons. Inspect the pistons for scuffing, scoring, cracks, pitting, or excessive ring groove wear. If these are evident, the piston must be replaced. The piston should also be checked in relation to the cylinder diameter.



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Fig. Fig. 8: Use a ring expander tool to remove the piston rings



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Fig. Fig. 9: Clean the piston grooves using a ring groove cleaner



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Fig. Fig. 10: You can use a piece of an old ring to clean the piston grooves, BUT be careful, the ring is sharp

  1. Using a telescoping gauge and micrometer, or a dial gauge, measure the cylinder bore diameter perpendicular (90%) to the piston pin, 2 1 / 2 in. (64mm) below the cylinder block deck (surface where the block mates with the heads). Then, with the micrometer, measure the piston perpendicular to its wrist pin on the skirt. If the difference between these measurements is within specifications or slightly below (after the cylinders have been bored or honed), finish honing is all that is necessary.
  2.  
  3. With a cylinder bore gauge, measure the cylinder bore for out-of-round and taper. Taper is the difference in wear between two bore measurements in any cylinder.Allowable out-of-round for the 2.5L engine is 0.002 in. (0.050mm) or less, and allowable taper is 0.005 in. (0.125mm) or less. For V6, V8 and V10 engines, maximum out-of-round is 0.005 in. (0.127mm), and maximum taper is 0.010 in. (0.254mm). If these specifications are exceeded, the cylinder block must be honed or re-bored and fitted with new pistons and rings.
  4.  

If one cylinder bore is rebored to a given oversize, all other sleeves must be rebored to the same oversize.

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Fig. Fig. 11: A telescoping gauge may be used to measure the cylinder bore diameter



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Fig. Fig. 12: Measure the piston's outer diameter using a micrometer

  1. If the clearance is excessive, try to obtain a slightly larger piston to bring clearance to within specifications. If this is not possible, obtain the first oversize piston and hone (or if necessary, bore) the cylinder to size.
  2.  



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Fig. Fig. 13: Checking the ring-to-ring groove clearance

  1. If the used piston is not acceptable, check the service piston size and determine if a new piston can be selected. Service pistons are available in standard, high limit and standard oversize.
  2.  



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Fig. Fig. 14: Critical dimensions of the stock factory piston-3.9L V6 engine



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Fig. Fig. 15: Critical dimensions of the stock factory piston-5.2L V8 engine

  1. If the cylinder bore must be reconditioned, measure the new piston diameter, then hone the cylinder bore to obtain the preferred clearance (refer to cylinder honing in this section).
  2.  



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Fig. Fig. 16: Critical dimensions of the stock factory piston-5.9L V8 engine



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Fig. Fig. 17: Diesel piston markings show which way faces front

  1. Select a new piston and mark the piston to identify the cylinder for which it was fitted. On some vehicles, oversize pistons may be found. These pistons will be 0.010 in. (0.254mm) oversize.
  2.  
  3. If the cylinder bore is in satisfactory condition, check the ring end-gap as follows:
    1. Compress the piston rings to be used in a cylinder, one at a time, into that cylinder.
    2.  
    3. Squirt clean oil into the cylinder, so that the rings and the top 2 in. (51mm) of cylinder wall are coated.
    4.  
    5. Using an inverted piston, press the rings approximately 1 in. (25mm) below the deck of the block. Measure the ring end-gap with the feeler gauge, and compare to the Ring Gap chart in this section.
    6.  
    7. If necessary, carefully pull the ring out of the cylinder and file the ends squarely with a fine file to obtain the proper clearance.
    8.  

  4.  
  5. Before checking the ring side clearance, be sure that the ring grooves are clean and free of carbon, sludge, or grit. Check the ring side clearance by installing rings on the piston, and inserting a feeler gauge of the correct dimension between the ring and the lower land. The gauge should slide freely around the ring circumference without binding. Any wear will form a step on the lower land. Remove any pistons having high steps.
  6.  



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Fig. Fig. 18: Check the piston ring side clearance with a feeler gauge as shown

  1. On diesels, insert the gauge between the ring and the upper land. If the piston grooves have worn to the extent that relatively high steps exist on the lower land, the piston should be replaced, because these will interfere with the operation of the new rings and ring clearance will be excessive.
  2.  

Piston rings are not furnished in oversize widths to compensate for ring groove wear.

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Fig. Fig. 19: Checking the piston ring gap

CYLINDER HONING



See Figures 20, 21 and 22

Unless you have experience and access to the proper equipment, cylinder honing and/or boring should be performed by a reputable, professional mechanic who has the know-how to do this critical job correctly. In some cases, clean-up honing can be done with the cylinder block in the vehicle, but most excessive honing and all cylinder boring must be done with the block stripped and removed from the vehicle.



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Fig. Fig. 20: Removing cylinder glazing using a flexible hone



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Fig. Fig. 21: A properly cross-hatched cylinder bore

  1. When cylinders are being honed, follow the manufacturer's recommendations for the use of the hone.
  2.  



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Fig. Fig. 22: The cylinder bore cross-hatch pattern should be at an approximately 50-60 degree angle as shown

  1. Occasionally, during the honing operation, the cylinder bore should be thoroughly cleaned and the selected piston checked for correct fit.
  2.  

Do not grind more than necessary to obtain specifications.

  1. When finish-honing a cylinder bore, the hone should be moved up and down at a sufficient speed to obtain a very fine uniform surface finish in a cross-hatch pattern of approximately 45-65° included angle. The finish marks should be clean but not sharp, and free from imbedded particles, torn or folded metal.
  2.  
  3. Permanently mark the piston for the cylinder to which it has been fitted and proceed to hone the remaining cylinders.
  4.  


WARNING
Handle the pistons with care. Do not attempt to force the pistons through the cylinders until the cylinders have been honed to the correct size. Pistons can be distorted through careless handling.

  1. Thoroughly clean the bores with hot water and detergent. Scrub well with a stiff bristle brush and rinse thoroughly with hot water. If is extremely essential that a good cleaning operation be performed. If any of the abrasive material is allowed to remain in the cylinder bores, it will rapidly wear the new rings and cylinder bores.
  2.  
  3. The bores should be swabbed several times with light engine oil and a clean cloth and then wiped with a clean dry cloth. CYLINDERS SHOULD NOT BE CLEANED WITH KEROSENE OR GASOLINE! Clean the remainder of
  4.  

the cylinder block to remove the excess material spread during the honing operation. PISTON PIN REPLACEMENT

See Figure 23

All of the gasoline engines covered in this guide utilize pressed-in wrist pins which can only be removed by an arbor press. The diesel piston pins are removed in the same way, except the pistons must be heated before the wrist pins are pressed out.



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Fig. Fig. 23: Use needlenosed or snapring pliers to remove the piston pin clip prior to pressing out the pin, and again after pin replacement

PISTON RING REPLACEMENT



See Figures 24, 25, 26, 27, 28, 29 and 30



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Fig. Fig. 24: A common factory top compression ring-1994-96 engines



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Fig. Fig. 25: A common factory second compression ring-1994-96 engines

A piston ring expander is necessary for removing the piston rings without damaging them; any other method (screwdriver, blades, pliers, etc.) usually results in the rings being bent, scratched or distorted, or the piston itself being damaged. When the rings are removed, clean the ring grooves using an appropriate ring groove cleaning tool, using care not to cut too deeply. Thoroughly clean all carbon and varnish from the piston with solvent.



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Fig. Fig. 26: Most rings are marked to show which side should face upward



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Fig. Fig. 27: Install chamfered rings as shown in this cross-sectional view

WARNING

The piston ring end-gap should also be checked while the rings are removed from the pistons. Incorrect end-gap indicates that the wrong size rings are being used, and ring breakage could occur again.



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Fig. Fig. 28: Piston ring gap positioning-V6 and V8 engines



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Fig. Fig. 29: Make sure the gap spacing is correct for each ring

Piston rings should be installed using a piston ring expander so that their ends are at three equal spacings. Avoid installing rings with their ends in-line with the piston pin bosses and the thrust direction. When installing new rings, refer to the installation diagram furnished with the new parts. Position the rings on the piston as illustrated; spacing of the various piston ring gaps is crucial to proper oil retention and even cylinder wear.



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Fig. Fig. 30: Piston ring gap locations on the V8 engine-V6 engine is similar

ROD BEARING REPLACEMENT



See Figures 31 and 32

Connecting rod bearings for the engines covered in this guide consist of two halves or shells which are interchangeable in the rod and cap. when the shells are placed in position, the ends extend slightly beyond the rod and cap surfaces so that when the rod bolts are torqued the shells will be clamped tightly in place to insure positive seating and to prevent turning. A tang holds the shells in place.

The ends of the bearing shells must never be filed flush with the mating surfaces of the rod and cap.

If a rod bearing becomes noisy or is worn so that its clearance on the crank journal is sloppy, a new bearing of the correct undersize must be selected and installed since there is no provision for adjustment.

WARNING

Under no circumstances should the rod end or cap be filed to adjust the bearing clearance, nor should shims of any kind be used.

Inspect the rod bearings while the rod assemblies are out of the engine. If the shells are scored or show flaking, they should be replaced. If they are in good shape, check for proper clearance on the crank journal (see the following). Any scoring or ridges on the crank journal means the crankshaft must be reground and fitted with undersized bearings, or replaced.

Make sure connecting rods and their caps are kept together, and that the caps are installed in the proper direction.

Replacement bearings are available in standard size, and in undersizes for a reground crankshaft. Connecting rod-to-crankshaft bearing clearance is checked using Plastigage® or an equivalent gauging material at either the top or bottom of each crank journal. the Plastigage® has a range of 0 to 0.003 in. (0.076mm).

  1. Remove the rod cap with the bearing shell. Completely clean the bearing shell and the crankshaft journal, and blow any oil from the oil hole in the crankshaft.
  2.  

The journal surfaces and bearing shells must be completely free of oil, because Plastigage® is soluble in oil.

  1. Place a strip of Plastigage® lengthwise along the bottom center of the lower bearing shell, then install the cap with shell and tighten the bolt or nuts to specification. DO NOT TURN the crankshaft with the Plastigage® installed in the bearing.
  2.  
  3. Remove the bearing cap with the shell. The flattened Plastigage® will be found sticking to either the bearing shell or crank journal. Do not remove it yet.
  4.  
  5. Use the printed scale on the Plastigage® envelope to measure the flattened material at its widest point. The number within the scale which most closely corresponds to the width of the Plastigage® indicated bearing clearance in thousandths of an inch.
  6.  
  7. Check the specifications chart in this section for the desired clearance. It is advisable to install a new bearing if clearance exceeds 0.003 in. (0.076mm); however, if the bearing is in good condition and is not being checked because of bearing noise, bearing replacement is not necessary.
  8.  
  9. If you are installing new bearings, try a standard size, then each undersize in order until one is found that is within the specified limits when checked for clearance with Plastigage®. Each under size has its size stamped on it.
  10.  



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Fig. Fig. 31: Apply a strip of gauging material to the bearing journal, then install and tighten the cap



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Fig. Fig. 32: After the cap is removed again, use the scale supplied with the gauging material to check clearances

  1. When the proper size shell is found, clean off the Plastigage® material from the shell, oil the bearing thoroughly, reinstall the cap with its shell and tighten the rod bolt nuts to specification.
  2.  

With the proper bearing selected and the nuts torqued, it should be possible to move the connecting rod back and forth freely on the crank journal as allowed by the specified connecting rod end clearance. If the rod cannot be moved, either the rod bearing is too far undersize or the rod is misaligned.

INSTALLATION



See Figures 23, 33, 34, 35, 36 and 37



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Fig. Fig. 33: Most pistons are marked to indicate their positioning in the engine



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Fig. Fig. 34: Position the valve cutouts in the piston head toward the manifold side of the engine-2.5L engine

If they were separated, install the connecting rod to the piston, making sure the piston installation notches and any marks on the rod are in proper relation to one another. Lubricate the wrist pin with clean engine oil and install the pin into the rod and piston assembly by using an arbor press as required. Install the wrist pin snaprings if equipped, and rotate them in their grooves to make sure they are seated.

Install the pistons in their original bores, if you are reusing the same pistons. Using a wooden hammer handle, push the rod into the bore while guiding the rod onto the journal.

On the 2.5L engine, position the valve cutouts in the piston head toward the manifold side of the engine. On all V6, V8 and V10 engines, the notch on the top of each piston must face the front of the engine. On diesel engines, position the piston in the cylinder with the front mark facing forward.

To position the connecting rod correctly, the larger chamfer of the lower connecting rod bore must face to the rear on the right bank and to the front on the left bank.



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Fig. Fig. 35: Piston and connecting rod assembly-2.5L engine



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Fig. Fig. 36: Make sure the piston and connecting rod assemblies are correctly positioned-V8 engine pistons shown

  1. Make sure the connecting rod bearings (including the end cap) are of the correct size and properly installed.
  2.  
  3. Fit rubber hoses over the connecting rod bolt to protect the crankshaft journals, as in the piston removal procedure. Coat the rod bearings with clean oil.
  4.  
  5. Using the proper ring compressor, insert the piston assembly into the cylinder so that the notch in the top of the piston faces the front of the engine (this assumes that the dimple or other markings on the connecting rods are in correct relation to the piston notch).
  6.  
  7. From beneath the engine, coat each crankshaft journal with clean oil. Pull the connecting rod, with the bearing shell in place, into position against the crankshaft journal.
  8.  
  9. Remove the rubber hoses. Install the bearing cap and cap nuts and tighten to specification.
  10.  



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Fig. Fig. 37: Installing the piston into the block using a ring compressor and the handle of a hammer

When more than one rod and piston assembly are being installed, the connecting rod cap attaching nuts should only be tightened enough to keep each rod in position until all have been installed. This will ease the installation of the remaining piston assemblies.

  1. Check the clearance between the sides of the connecting rods and the crankshaft using a feeler gauge. Spread the rods slightly with a screwdriver to insert the gauge. If clearance is below the minimum tolerance, the rod may be machined to provide adequate clearance. If clearance is excessive, substitute an unworn rod, and recheck. If clearance is still outside specifications, the crankshaft must be welded and reground, or replaced.
  2.  
  3. Install the oil pump if removed, and the oil pan.
  4.  
  5. Install the cylinder head(s) and intake manifold.
  6.  

 
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