The 1997 Nissan Altima had only one engine, according to Auto Zone -- the 2.4-liter sequential fuel-injected double overhead cam engine. The timing chain, like timing belts, do stretch, but last much longer than a timing belt. The chain usually lasts closer to 100,000 to 120,000 miles. You can also hear the chain rattle if it gets too loose. Once you hear the rattle, you need to change the timing chain, as the engine will eventually stop running because it is out of time.
Disconnect the negative battery cable, using the appropriate wrench. Set it aside, ensuring that it does not touch metal. Slide one of the drain pans under the radiator petcock. Open the petcock and loosen the radiator cap to allow the coolant to drain.
Jack the vehicle up, using the floor jack, then support it with jack stands. Slide the other drain pan under the oil pan. Loosen the drain bolt, using the appropriate socket and allow the oil to drain.
Remove the engine undercover, using the appropriate socket. Lower the vehicle off the jack stands, using the floor jack. Label all vacuum lines and wiring harness connectors, using the tape and marker.
Loosen the lock nut on the adjusting bolt for the alternator. Loosen the adjusting bolt to relieve tension on the belt. Lift the belt off the alternator pulley. Unplug the wiring harness connector on the back of the alternator. Remove the power wire, using the appropriate wrench. Screw the nut back onto the stud, so you don't lose it. Unbolt and remove the alternator bracket, using the appropriate socket.
Loosen the clamp on the air duct, using the screwdriver, then pull the air duct off the air box. Remove the front exhaust tube, using the appropriate socket. Remove the intake manifold collector supports, the intake manifold collector and the exhaust manifold, using the appropriate sockets.
Pull the spark plug wire off the No. 1 spark plug. This is the plug closest to the front of the engine -- or the side with the belts. Remove the spark plug, using the spark plug socket. Pull the coil wire off the distributor. Stick the long screwdriver into the spark plug hole and rest it on the top of the piston. Turn the engine over using a socket on the crankshaft pulley while holding the screwdriver. When the piston comes up to the top of the bore, stop turning. When it gets to the top, the screwdriver stops moving, until it starts to go down again, in which case you've gone too far.
Remove the distributor cap. If the rotor is not pointing to the No. 1 cylinder, turn the engine over again, until you feel the piston come to the top of the cylinder. The rotor should be pointing at the No. 1 cylinder. Unplug the wiring harness connectors on the distributor. Remove the distributor, using the appropriate socket.
Place the block of wood on the floor jack. Slide the jack under the oil pan and jack it up until it supports the oil pan. Remove the passenger side engine mount, using the appropriate socket.
Remove the valve cover, using the appropriate socket. Hold the camshaft sprockets with a wrench, then unbolt them, using the appropriate socket. Remove the camshaft sprockets. Remove the cam bearing caps in the proper order (see Resources) and lay the cap out as you take them off. They must be reinstalled in the same place.
Remove the head bolts according to the diagram to the diagram (see Resources). Remove the cam sprocket cover, upper timing chain tensioner and upper chain guides, using the appropriate sockets. Remove the upper timing chain. Remove the idler sprocket bolt.
Lift the head and gasket off the engine. Remove the oil pan, using the appropriate socket. Remove the crankshaft damper, using the appropriate socket. Remove the front cover. Remove the oil pump drive spacer. Remove the lower timing chain tensioner, tensioner arm and lower timing chain guide, using the appropriate sockets. Remove the lower timing chain, lower sprocket, and idler sprocket.
Clean the gasket-mating surfaces on the head and cover, using the plastic scraper and shop rags. Install the crankshaft sprocket and oil pump drive spacer. Make sure the timing marks on the crankshaft sprocket are facing the front of the engine. Reinstall the idler sprocket and lower timing chain, ensuring the mating marks on the chain are lined up with the marks on the sprocket. The mating marks on the timing chain are usually silver.
Reinstall the chain tensioner and the chain guide. Reinstall the lower timing chain tensioner. Install a new front cover seal. Apply a 2 mm bead of RTV silicone on the timing cover and allow it to skin over. It is ready when it doesn't stick to your finger when you touch it.
Reinstall the front cover. Tighten the M6 bolts to 60 inch-pounds of torque. Tighten the M8 bolts to 13 foot-pounds of torque. Reinstall the crankshaft damper. Reinstall the oil strainer and the oil pan. Install the cylinder head. Coat the head bolt threads with engine oil. Insert the bolts, and temporarily tighten them snugly -- do not torque them.
Install the upper timing chain, upper timing chain tensioner and the chain guide. Set the upper timing chain on the idler sprocket, ensuring that the mating marks line up. Apply a 2 mm bead of RTV silicone on the cam sprocket cover. Allow it to skin over. Install the cover.
Tighten the head bolts in the proper order (see Resources). Reinstall the camshafts and bearing caps. Fit the chain onto the camshaft sprockets, then install the sprockets and chain as an assembly. Install the chain guide between both camshaft sprockets. Ensure that the alignment marks on the upper part of the timing chain are aligned.
Reinstall the distributor. Make sure the rotor is pointing at the No. 1 cylinder. Reinstall the valve cover and tighten the bolts firmly. Reinstall the rest of the parts in reverse order of removal. Refill the radiator and oil (refer to the owner's manual for the viscosity and amount of engine oil).
Reconnect the negative battery cable. Start the engine and allow it to come to operating temperature. Top off the coolant as needed.
