Engine Mechanical - 2.5L: Overhaul Nissan Altima L31

DISASSEMBLY AND ASSEMBLY

Note. Flywheel removal may require use of special tool J-46531 (TP55 Torx Plus driver) for M/T flywheel bolts. See ESSENTIAL TOOL: TORX DRIVER FOR FLYWHEEL BOLTS for more information.

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1. Remove the engine and transaxle as an assembly from the vehicle, and separate the transaxle from the engine. Refer to «Removal and Installation»(ref-159291-S35168916562005042600000) .
2. Mount the engine on a suitable engine stand.
3. Drain any remaining engine oil and coolant from the engine.
4. Remove the following components and associated parts. Exhaust manifold and three way catalyst assembly. Refer to «Removal and Installation»(ref-159291-S31306336392005042600000) . Intake manifold collector. Refer to «Removal and Installation»(ref-159291-S11754672062005042600000) . Intake manifold and fuel tube assembly. Refer to «Removal and Installation»(ref-159291-S11754672062005042600000) . Ignition coils. Refer to «Removal and Installation»(ref-159291-S21443364292005042600000) . Rocker cover. Refer to «Removal and Installation»(ref-159291-S12621124542005042600000) . Front cover, timing chain, and balancer unit. Refer to «Removal and Installation»(ref-159291-S16683729202005042600000) . Cylinder head. Refer to «Removal and Installation»(ref-159291-S22497270452005042600000) .
5. Remove the knock sensor. CAUTION: Carefully handle the sensor and do not drop the sensor.
6. Remove crankshaft position sensor (POS). CAUTION: Avoid impacts such as a dropping. Do not disassemble. Keep it away from metal particles. Do not place sensor close to magnetic materials.
7. Remove the flywheel (M/T models) or drive plate (A/T models). Hold the crankshaft with a stopper plate and remove the mounting bolts. CAUTION: Be careful not to damage the flywheel contact surface for the clutch disc. NOTE: The flywheel two-block construction allows movement in response to transmission side pressure, or when twisted in its rotational direction, therefore, some amount of noise is normal.
8. Remove pilot converter using Tool (A/T models).
9. Remove the piston and connecting rod assemblies. Position the crankshaft and corresponding connecting rod, to be removed, to the bottom dead center stroke. Remove the connecting rod cap. Number the cap so it can be assembled in the same position. Using a hammer handle or similar tool, push the piston and connecting rod assembly out of the top of the cylinder block. Number the piston and rod so it can be assembled in the same position. Before removing the piston and connecting rod assembly, check the connecting rod side clearance. Refer to «CONNECTING ROD SIDE CLEARANCE»(ref-159291-S16406913872005042600000) .
10. Remove the connecting rod bearings. If reusing, number them so they can be assembled in the same position and direction. CAUTION: When removing them, note the installation position. Keep them in the correct order.
11. Remove the piston rings from the piston. Use a piston ring expander. CAUTION: When removing the piston rings, be careful not to damage the piston. Be careful not to damage piston rings by expanding them excessively, if reusing them. Before removing the piston rings, check the piston ring side clearance. Refer to «PISTON RING SIDE CLEARANCE»(ref-159291-S30504774302005042600000) .
12. Remove the piston from the connecting rod as follows. Using a snap ring pliers, remove the two snap rings. Heat the piston to 60° - 70°C (140° - 158°F) with a heat gun, or equivalent. Push out piston pin with a punch of an outer diameter of approximately 19 mm (0.75 in).
13. Remove the lower cylinder block mounting bolts. Before loosening the lower cylinder block mounting bolts, measure the crankshaft side clearance. Refer to «CRANKSHAFT SIDE CLEARANCE»(ref-159291-S27766096752005042600000) . Loosen them in the order shown to remove them.
14. Remove the lower cylinder block. Using Tool (seal cutter) cut the RTV Silicone Sealant and remove the lower cylinder block from the cylinder block. CAUTION: Be careful not to damage the mounting surface.
15. Remove the crankshaft.
16. Pull the rear oil seal out of the rear end of the crankshaft.
17. Remove the main bearings and thrust bearings from the cylinder block and lower cylinder block.

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1. Using compressed air, clean out the coolant and oil passages in the cylinder block, the cylinder bore and the crankcase to remove any foreign material. CAUTION: Use approved safety glasses to protect your eyes.
2. Install the drain plugs on the cylinder block. Apply RTV Silicone Sealant. Use Genuine RTV Silicone Sealant, or equivalent. Refer to RECOMMENDED CHEMICAL PRODUCTS AND SEALANTS . Replace the copper washers with new ones.
3. Install the main bearings and the thrust bearings. Remove dust, dirt, and oil from the bearing mating surfaces of the cylinder block and lower cylinder block. Install the thrust bearings to both sides of the No. 3 main bearing journal on the cylinder block. Install the thrust bearings with the oil groove facing the crankshaft arm (outside). Install the main bearings paying attention to their position and direction. The main bearing with an oil hole and groove goes on the cylinder block. The one without them goes on the lower cylinder block. Only the main bearing (on the cylinder block) for No. 3 journal has different specifications. Before installing the bearings, apply engine oil to the bearing friction surface (inside). Do not apply oil to the back surface, but thoroughly clean it. When installing, align the bearing stopper to the notch. Make sure that the oil holes on the cylinder block and those on the corresponding bearing are aligned.
4. Install the signal plate to the crankshaft. Signal plate bolts : 12 - 14 N.m (1.22 - 1.43 kg-m, 9 - 10 ft-lb) Position the crankshaft and signal plate using a positioning dowel pin, and tighten the mounting bolts to specification. Remove the dowel pin. CAUTION: Be sure to remove dowel pin before installing the crankshaft. NOTE: Dowel pins for the crankshaft and signal plate are supplied as a set for each.
5. Install the crankshaft onto the cylinder block. While turning the crankshaft by hand, check that it turns smoothly.
6. Install the lower cylinder block. Apply RTV Silicone Sealant to positions shown in the figure. NOTE: Cylinder block and lower cylinder block are machined together. Neither of them can be replaced separately. CAUTION: After the RTV Silicone Sealant is applied, the lower cylinder block installation must be finished within 5 minutes.
7. Tighten lower cylinder block mounting bolts in the numerical order shown and according to the following steps: Apply new engine oil to threads and seat surfaces of the mounting bolts. Tighten bolts No. 1 - 10 only in the order shown, to specification below. First tightening, bolts 1 - 10 only : 36.3 - 42.2 N.m (3.7 - 4.3 kg-m, 27 - 31 ft-lb) Tighten bolts No. 1 - 10 only in the order shown, to specification below. CAUTION: Use an angle wrench (special service tool) or protractor to check tightening angle. Do not make judgment by visual inspection. Second tightening, bolts 1 - 10 only : 60° - 65° degrees rotation (target: 60° degrees) Tighten bolts No. 11 - 22 only in the order shown, to specification. Third tightening, bolts 11 - 22 only : 19.6 - 24.5 N.m (2.0 - 2.5 kg-m, 15 - 18 ft-lb) Wipe off completely any protruding RTV Silicone Sealant on the exterior of engine. Check crankshaft side clearance. Refer to «CRANKSHAFT SIDE CLEARANCE»(ref-159291-S27766096752005042600000) . After installing the mounting bolts, make sure that the crankshaft can be rotated smoothly by hand.
8. Install the rear oil seal. Press the oil seal between cylinder block and crankshaft with a suitable drift. Be careful not to touch the grease on the oil seal lip. Be careful not to cause scratches or burrs when pressing in the rear oil seal. Press in rear oil seal to the position shown in the figure.
9. Install the piston to the connecting rod. Assemble the components in their original positions. Using a snap ring pliers, install the snap ring to the grooves of the piston's rear side. Insert the piston pin snap ring fully into groove. Install the piston to the connecting rod. Using a heat gun, heat the piston [approximately 60° - 70 C° (140° - 158 °F)] until the piston pin can be pushed in by hand without excessive force. From the front to the rear, insert the piston pin into the piston and the connecting rod. Assemble so that the front mark on the piston crown and the oil holes and the cylinder No. on the connecting rod are positioned as shown in the figure. Install the piston pin snap ring into the front of the piston. Check that the connecting rod moves smoothly.
10. Using a piston ring expander, install the piston rings. Assemble the components in their original positions. CAUTION: Be careful not to damage the piston. Position each ring with the gap as shown in the figure, referencing the piston front mark as the starting point. Install the top ring and the second ring with the stamped surface facing upward. Stamped mark : A (top ring) : 2A (second ring)
11. Install the connecting rod bearings to the connecting rod and the connecting rod cap. Assemble the components in their original positions. When installing the connecting rod bearings, apply engine oil to the bearing friction surface (inside). Do not apply oil to the back surface, but thoroughly clean the back. When installing, align the connecting rod bearing stopper protrusion with the notch of the connecting rod to install. Check the oil holes on the connecting rod and those on the corresponding bearing are aligned.
12. Install the piston and connecting rod assembly to the crankshaft. Assemble the components in their original positions. Rotate the crankshaft so the pin corresponding to the connecting rod to be installed is at the bottom dead center position. Apply engine oil sufficiently to the cylinder bore, piston, and crankshaft pin. Match the cylinder position number with the cylinder No. on the connecting rod for installation. Using a piston ring compressor, install the piston with the front mark on the piston crown facing the front of the engine. CAUTION: Be careful not to damage the crankshaft pin, resulting from an interference of the connecting rod big end.
13. Install the connecting rod caps. Assemble the components in their original positions. Match the stamped cylinder number marks on the connecting rod with those on the cap to install.
14. Tighten the connecting rod bolt as follows: Apply engine oil to the threads and seats of the connecting rod bolts. CAUTION: Always use either an angle wrench or protractor. Avoid tightening based on visual check alone. Stage 1 : 18.6 - 20.6 N.m (1.9 - 2.1 kg-m, 14 - 15 ft-lb) Stage 2 : Rotate bolts 85° - 95° degrees (target 90° degrees) Check the connecting rod side clearance. Refer to «CONNECTING ROD SIDE CLEARANCE»(ref-159291-S16406913872005042600000) . After tightening the bolts, make sure that the crankshaft rotates smoothly.
15. Install flywheel (M/T Models), or drive plate (A/T Models). Install drive plate, reinforcement plate and pilot converter as shown in figure. Using a drift with 33 mm (1.30 in) diameter, push pilot converter into the end of the crankshaft.
16. Install the knock sensor. Make sure that there is no foreign material on the cylinder block mating surface and the back surface of the knock sensor. Install the knock sensor with the connector facing lower left by 45° as shown. Do not tighten the mounting bolts while holding the connector. Make sure that the knock sensor does not interfere with other parts. Knock sensor bolt : 15.7 - 26.5 N.m (1.6 -2.7 kg-m, 12 - 19 ft-lb) CAUTION: If the knock sensor is dropped, replace it with new one.
17. Install the crankshaft position sensor (POS). Crankshaft position sensor bolt : 5.4 - 7.3 N.m (0.55 - 0.75 kg-m, 48 - 65 in-lb)
18. Remaining installation is in the reverse order of removal.

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1. The identification grade stamped on each part is the grade for the dimension measured in new condition. This grade cannot apply to reused parts.
2. For reused or repaired parts, measure the dimension accurately. Determine the grade by comparing the measurement with the values of each selection table.
3. For details of the measurement method of each part, the reuse standards, and the selection method of the selective fitting parts, refer to the text.

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1. Check the cylinder bore grade on rear left side of cylinder block, and select a piston of the same grade.
2. If there is a corrected stamp mark on the cylinder block, use it as a correct reference.