Honda Accord/Prelude 1984-1995 Repair Guide

Pistons and Connecting Rods

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REMOVAL



See Figures 1, 2, 3, 4 and 5

This procedure requires removal of the head and oil pan. It is much easier to perform this work with the engine removed from the vehicle and mounted on a stand. These procedures require certain hand tools which may not be in your tool box. A cylinder ridge reamer, a numbered punch set, piston ring expander, snapring pliers and piston installation tool (ring compressor) are all necessary for proper piston and rod repair. These tools are commonly available from retail tool suppliers; you may be able to rent them from larger automotive supply houses.

  1. If the pistons and rods are being removed as part of a complete tear-down, follow the procedures described in Crankshaft and Main Bearings in this section. If you are removing the pistons and connecting rods without removing the crankshaft and main bearings, proceed from this point.
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  3. Remove the cylinder head(s), following the procedures given in this section.
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  5. Remove the oil pan.
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  7. On engines so equipped, it will be necessary to remove the main bearing cap bridge assembly. This is secured by a series of bolts. Loosen the bolts using the correct sequence (refer to the crankshaft procedures in this section).
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  9. The connecting rods are marked to indicate which surface faces front, but the bearing caps should be matchmarked before disassembly. Use a number punch set and a small hammer to mark the number (of the cylinder) over the seam so that each piece will be reused in its original location. Note that the rods and bearing caps may already have numbers stamped on them; these are indicators of original bearing thickness, not of location or sequence.
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  11. Remove the connecting rod cap nuts, pull the caps off the rods and place them on a bench in order.
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Fig. Fig. 1: Remove the nuts securing the cap ...



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Fig. Fig. 2: ... then remove the cap from the engine

  1. Inspect the upper portions of the cylinder (near the head) for a ridge formed by ring wear. If there is a ridge, it must be removed by first shifting the piston down in the cylinder and then covering the piston top completely with a rag soaked with clean engine oil. Use a ridge reamer to remove metal at the lip until the cylinder is smooth. If this is not done, the pistons may be damaged during removal. Remove the rag and all the metal chips; use a magnet if necessary.
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Fig. Fig. 3: Remove the ridge at the top of the bore with a ridge cutter

  1. Place pieces of rubber hose over the bolts to keep the ends from scoring the cylinder and journals. Use a piece of wood or a hammer handle under the piston to tap it upward. If you're working on an engine with the crankshaft still in place, turn the crankshaft until the crankpin for each cylinder is in a convenient position. Be careful not to subject the piston and/or rod to heavy impact and do not allow the piston rod to damage the cylinder walls on the way out. The slightest nick in the metal can cause problems after reassembly.
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Fig. Fig. 4: Place lengths of rubber hose over the connecting rod studs in order to protect the crankshaft and cylinders from damage



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Fig. Fig. 5: Carefully tap the piston out of the bore using a wooden dowel or hammer handle

  1. Clean the pistons, rings, and rods in parts solvent with a soft bristle brush. Do not use a wire brush even to remove heavy carbon. The metal may become damaged. Use a ring groove cleaner or a piece of a broken piston ring to clean the lands (grooves) in the piston.
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CAUTION
Wear goggles and gloves during cleaning. Do not spatter solvent onto painted surfaces.

CONNECTING ROD BEARING REPLACEMENT



See Figures 6 and 7

Connecting rod bearings on all Honda engines consist of two halves or shells which are not interchangeable in the rod and cap. When the shells are in position, the ends extend slightly beyond the rod and cap surfaces so that when the bolts are tightened, the shells will be clamped tightly in place. This insures positive seating and prevents turning. A small tang holds the shells in place within the cap and rod housings.

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

If a rod becomes noisy or is worn so that its clearance on the crankshaft is sloppy, a new bearing of the correct undersize must be selected and installed. There is no provision for adjustment. Under no circumstances should the rod end or cap be filed to compensate for wear, nor should shims of any type be used.

Inspect the rod bearings while the rods are out of the engine. If the shells are scored or show flaking they should be replaced. ANY scoring or ridge on the crankshaft means the crankshaft must be replaced. Because of the metallurgy in the crankshaft, welding and/or regrinding the crankshaft is not recommended.

Replacement bearings are available in standard sizes, usually marked either on the bearing shell or possibly on the rod cap. Do not confuse the mark on the bearing cap with the cylinder number. For example, it is quite possible that the No. 3 piston rod contains a number 1 size bearing. The rod cap may have a "1" marked on it (stamped at the factory indicating the bearing size). You should have stamped a "3" or other identifying code on both halves of the rod during disassembly to indicate the cylinder number.

Measuring the clearance between the connecting rod bearings and the crankshaft (oil clearance) is done with a plastic measuring material such as Plastigage® or similar product.

  1. Remove the rod cap with the bearing shell. Completely clean the cap, bearing shells and the journal on the crankshaft. Blow any oil from the oil hole in the crank. The plastic measuring material is soluble in oil and will begin to dissolve if the area is not totally free of oil.
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  3. Place a piece of the measuring material across the crank journal. Install the cap and shell and tighten the bolts in three passes to the correct torque.
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Fig. Fig. 6: Place a piece of the measuring material across the crank journal, then install and torque the cap

Do not turn the crankshaft with the measuring material installed.

  1. Remove the bearing cap with the shell. The flattened plastic material will be found sticking to either the bearing shell or the crank journal. DO NOT remove it yet.
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  3. Use the scale printed on the packaging for the measuring material to measure the flattened plastic at its widest point. The number within the scale which is closest to the width of the plastic indicates the bearing clearance in thousandths of an inch. Note this measurement, then remove the gauging material.
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Fig. Fig. 7: After the bearing cap has been removed, use the gauge supplied with the material to check the clearance

  1. Check the specifications chart in this section for the proper clearance. If there is any measurement approaching the maximum acceptable value, replace the bearing.
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  3. When the correct bearing is obtained, oil the bearing thoroughly on its working face and install it in the cap. Install the other half of the bearing into the rod end and attach the cap to the rod. Tighten the nuts evenly, in three passes to the proper value.
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  5. With the proper bearing installed and the nuts properly tightened, it should be possible to move the connecting rod back and forth a bit on the crankshaft. If the rod cannot be moved, either the bearing is too small or the rod is misaligned. Check the connecting rod side-play (refer to the crankshaft and main bearing procedures in this section).
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INSPECTION



See Figures 8, 9, 10, 11, 12, 13, 14 and 15

  1. Measure the bore of the cylinder at three levels and in two dimensions (fore-and-aft and side-to-side). That's six measurements for each cylinder. By comparing the 3 vertical readings, the taper of the cylinder can be determined and by comparing the front-rear and left-right readings the out-of-round can be determined. The block should be measured: at the level of the top piston ring at the top of piston travel; in the center of the cylinder; and at the bottom. Compare your readings with the specifications in the chart.
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Fig. Fig. 8: Six measurements are required for each cylinder

  1. If the cylinder bore is within specifications for taper and out-of-round and the wall is not scored or scuffed, boring of the cylinder is not needed. If not within specifications. it should be bored oversize, as necessary, to insure elimination of out-of-round and taper. Under these circumstances, the block should be taken to a machine shop for proper boring by a qualified machinist using specialized equipment.
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If the cylinder is bored, oversize pistons and rings must be installed. Since all pistons must be the same size, all cylinders must be rebored if any one is out of specification.

  1. Even if the cylinders do not require boring, they must be fine-honed for proper break-in. A deglazing tool may be used in a power drill to remove the glossy finish on the cylinder walls. Use only the smooth stone-type hone, not the beaded or "bottle brush" type.
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Fig. Fig. 9: Use only a smooth stone-type hone

  1. The cylinder head top deck (gasket surface) should be inspected for warpage. Run a straightedge along all four edges of the block, across the center and diagonally. If you can pass a feeler gauge of 0.004 in (0.1mm) under the straightedge, the top surface of the block should be machined or trued.
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Fig. Fig. 10: Inspect the deck of the engine block for warpage

  1. The rings must be removed from the pistons with a ring expander. Keep all rings in order and with the piston from which they were removed. The rings and piston ring grooves should be cleaned thoroughly as deposits will alter readings of ring wear.
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Fig. Fig. 11: Use a ring expander to remove the rings from the pistons



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Fig. Fig. 12: Clean the grooves using a ring groove cleaner

  1. Before any measurements are begun, visually examine the piston (a magnifying glass is helpful) for any signs of cracks, particularly in the skirt area. Anything other than light surface scoring disqualifies the piston from further use. The metal will become unevenly heated and the piston may break apart during use.
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  3. Piston diameter should be measured at the skirt, at right angles to the piston pin. Compare the measurement either with the specified piston diameter or subtract the diameter from the cylinder bore dimension to get clearance. If clearance is excessive, the piston should be replace. If a new piston still does not produce piston-to-wall clearance within specifications, select an oversize piston and have the cylinders bored accordingly.
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Fig. Fig. 13: Measure the piston skirt diameter

  1. Compression ring side clearance should be measured by using a ring expander to put cleaned rings back in their original positions on the pistons. Measure side clearance on one side by attempting to slide a feeler gauge of the thickness specified between the ring and the edge of the ring groove. If the gauge will not pass into the groove, the ring may be re-used although new rings are always recommended. If the gauge will pass, but a gauge of slightly greater thickness representing the wear limit will not, the piston may be reused, but new rings must be installed.
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Fig. Fig. 14: Check the ring side clearance with a feeler gauge

  1. Ring end gap must be measured for all three rings in the cylinder by using a piston to (upside down) to press the ring squarely into the cylinder. The rings must be between 0.6-0.8 in. (15-20mm) from the bottom of the cylinder. Use a feeler gauge to measure the end-gap and compare it with specifications. If the gap is too great, the ring should be checked with a gauge representing the wear limit. If cylinder bore wear is very slight, you may use new rings to bring the end-gap to specification without boring the cylinder. Measure the gap with the ring located near the minimum dimension at the bottom of the cylinder, not near the top where wear is greatest.
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Fig. Fig. 15: Install the ring near the bottom of the cylinder to measure the end gap

  1. The connecting rods must be free from wear, cracking and bending. Visually examine the rod, particularly at its upper and lower ends. Look for any sign of metal stretching or wear. The piston pin should fit cleanly and tightly through the upper end, allowing no sideplay or wobble. The bottom end should also be an exact 1 / 2 circle with no deformity of shape. The bolts must be firmly mounted and parallel. The rods may be taken to a machine shop for exact measurement of twist or bend. This is generally cheaper and easier than purchasing a seldom-used rod alignment tool.
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PISTON PIN REPLACEMENT



The piston pins or wrist pins are press fitted into place. Special tools including an adjustable pin driver, pilot collar, and spring loaded piston pin assembly jig are required as well as access to a hydraulic press. The piston pins cannot be removed by any common method in the average garage. If the pins must be removed, take the pistons to a reputable machine shop.

INSTALLATION



See Figures 16, 17, 18 and 19

  1. Remember that if you are installing oversize pistons, you must also use new rings of the correct oversize.
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  3. Install the rings on the piston, lowest ring first. This requires the use of a ring expander. There is a high risk of ring breakage or piston damage if the rings are installed without the expander. The correct spacing of the ring end gaps is critical to oil control. No two gaps should align; they should be evenly spaced around the piston with the gap in the oil ring expander facing the front of the piston (aligned with the mark on the top of the piston). Once the rings are installed, the pistons must be handled carefully and protected from dirt and impact.
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Fig. Fig. 16: The rings must be installed in their correct locations



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Fig. Fig. 17: Align the ring gaps as shown

  1. Install the number two compression ring next and then the top compression ring using the ring expander. Note that these rings have the same thickness but different cross-sections or profiles; they must be installed in the proper locations. Make sure all markings face upward and that the gaps are all staggered. Gaps must also not be in line with either the piston pin or thrust faces of the piston.
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  3. All the pistons, rods, and caps must be reinstalled in the correct cylinder. Make certain that all labels and stamped numbers are present and legible. Double check the piston rings; make certain that the gaps do NOT line up and are properly spaced around the piston (refer to the illustration). Double check the bearing insert at the bottom of the rod for proper mounting. Reinstall the protective pieces of rubber hose on the rod bolts.
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  5. Liberally coat the cylinder wall and the crankshaft journals with clean, fresh motor oil. Also apply oil to the bearing surfaces on the connecting rod and the cap.
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  7. Identify the FRONT mark on each piston and rod. Position the piston and rod assembly loosely in each cylinder with the marks facing the front or timing belt end of the engine. Make certain the number stamped on each piston corresponds to the number of the cylinder.
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WARNING
Failure to observe the marking and its correct placement can lead to sudden and catastrophic engine failure.

  1. Install the ring compressor around one piston and tighten it gently until the rings are compressed almost completely.
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Fig. Fig. 18: A ring compressor must be used to install the piston in the block

  1. Gently press down on the piston top with a wooden hammer handle or similar soft faced tool; drive the piston into the cylinder bore. Once all three rings are in the bore, the piston will move with some ease.
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WARNING
If any resistance or binding is encountered during the installation, DO NOT apply force. Tighten or adjust the ring compressor and/or reposition the piston. Brute force will break the ring(s) or damage the piston.

  1. From underneath, pull the connecting rod into place on the crankshaft. Remove the rubber hoses from the bolts. Check the rod cap to confirm that the bearing is present and correctly mounted, then install the rod cap (observing the correct number and position and its nuts. Leaving the nuts finger-tight will make installation of the remaining pistons easier.
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  3. With all the pistons installed and the bearing caps secured finger-tight, the retaining nuts may be tightened to their final setting. Refer to the torque specifications chart in this section. For each pair of nuts, make 3 passes alternating between the two nuts on any given rod cap. The three tightening steps should be about one third of the final torque; for example, if the final torque is 36 ft. lbs., draw the nuts tight in steps to 12, 24 and then 36 ft. lbs. The intent is to draw each cap up to the crank straight and under even pressure.
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Fig. Fig. 19: Always use a torque wrench to tighten the bearing cap nuts

  1. Turn the crankshaft through several rotations, making sure everything moves smoothly and there is no binding. With the piston rods connected, the crank may be stiff to turn. Try to turn it in a smooth continuous motion so that any stiff spots may be felt.
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  3. If equipped with a main bearing cap bridge, loosen the main bearing cap bolts, then tighten the cap and bridge bolts using the proper sequence (refer to the crankshaft procedures in this section).
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  5. Reinstall the oil pan. Even if the engine is to remain apart for other repairs, install the pan to protect the bottom end. Install all the pan bolts and tighten them to the correct tightness; this eliminates one easily overlooked item during future reassembly.
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  7. If the engine is to remain apart for other repairs, pack the cylinders with crumpled newspaper or clean rags to keep out dust and grit; cover the top of the cylinders with a large rag. If the engine is on a stand, the entire block can be covered with a large trash bag.
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  9. If no further work is to be performed, continue reassembly by installing the head, timing belt, etc.
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  11. When the engine is restarted after assembly, the exhaust will be very smoky as the oil within the cylinders burns off. This is normal; the smoke should clear quickly during warm up. Depending on the state of the spark plugs, it may be wise to check for any oil fouling on the spark plugs after the engine is shut off.
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  13. A reminder: once the engine is assembled and driveable, remember that you are breaking in an essentially new engine-follow the break-in interval as you would for a new car.
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