The LS400 used the same 4.0L engine from 1995 through 2000. It is an interference engine, which means that because of the close tolerances, should the timing belt stretch past the scope of the tensioner, the valves will most likely hit the pistons and cause extensive damage. Lexus recommends changing the timing every 60,000 miles for model years 1995 through 1997, and every 90,000 miles for model years 1998 through 2000. Several special tools are needed to complete the job, and all are available at any Lexus dealership.
Disconnect the battery negative cable and lay it aside, ensuring that it does not touch metal. Remove the engine splash guard using the appropriate socket. Place the drain pan under the radiator drain plug. Loosen the drain plug and allow the radiator to drain. If the drain pan is clean, you can reuse the antifreeze.
Remove intake air trunking (the hose on the air filter) using the appropriate sockets. Loosen the accessory drive belt tensioners, relieving tension on the accessory drive belts. Lift the belts off the pulleys. Remove the fan, coupling, fan pulley and drive belt tensioner pulley using the appropriate sockets. Pull the wiring out of its holder on the upper-right timing belt cover.
Remove the right and left distributors, paying particular attention to which distributor goes where, and which bolts go with each distributor. The bolts are different lengths.
Unbolt and remove the left ignition coil using the appropriate sockets. Unscrew the oil cooler pipe and remove it. Unbolt the air compressor, but do not remove the hoses. Move it to the side. Remove the left and right upper timing belt covers, centre timing belt cover and the fan bracket using the appropriate sockets.
Loosen the crankshaft pulley bolt using the holder and the handle. Turn the crankshaft clockwise until the crankshaft timing mark lines up at the 11 o’clock position. Check the timing marks on the camshafts. If both are not lined up, turn the crankshaft one more turn, then the camshaft timing marks will line up at the 12 o’clock position.
Turn the crankshaft an additional 50 degrees until the pulley timing mark (a notch in the pulley) lines up with the guide pulley bolt. The camshaft sprocket timing marks will move forward by 25 degrees.
Remove the crankshaft pulley bolt, the auto tensioner bolts, the auto tensioner and the auto tensioner dust boot using the appropriate sockets. Unhook the timing belt from the camshaft sprockets. Remove the crankshaft pulley using the puller, taking care not to turn the crankshaft and disturb the timing marks.
Remove the alternator, lower timing belt cover and the timing belt guide washer using the appropriate sockets. Lift the timing belt off the sprockets and pulleys. Check the auto tensioner for oil leakage. If oil is leaking, replace the tensioner. Keeping the tensioner upright, press it against a wall or other hard surface. If you can move the pushrod, replace the tensioner. Measure the pushrod protrusion. If the measurement is not between 0.413 and 0.453 inches, replace the auto tensioner.
Insert the tensioner in the press. Using a force of 220 to 2,205 pounds, push the pushrod into the auto tensioner until the hole in the pushrod lines up with the hole in the auto tensioner body. Insert an Allen wrench to hold the pushrod in place. Install the dust boot on the auto tensioner.
Install the timing belt on the crankshaft sprocket, ensuring the “CR” mark on the timing belt lines up with the timing mark on the sprocket. Bring the belt up and behind the tensioner pulley and the guide pulley. Make sure the direction of rotation markings is pointing clockwise.
Install the timing belt guide washer, lower timing belt cover and the crankshaft pulley, making sure that the timing mark on the crankshaft pulley lines up with the guide pulley bolt. Install the alternator.
Install the timing belt on the right camshaft sprocket (as you are looking down at the engine), keeping tension on the belt between the crankshaft sprocket, guide pulley and the camshaft sprocket. The camshaft is marked L-CAM. Route the timing belt over the left camshaft sprocket (R-CAM), making sure the timing mark on the belt lines up with the mark on the sprocket. Keep the belt taut between the sprockets.
Install the auto tensioner. Tighten the bolts to 19 foot-pounds of torque. Remove the Allen wrench from the auto tensioner, allowing the auto tensioner to put tension on the belt. Temporarily install the crankshaft pulley bolt. Turn the crankshaft slowly for almost two turns until the crankshaft timing mark lines up with the timing mark at the 11 o’clock position. Check that all three timing marks (cams and crank) are lined up. If the marks do not line up, remove the belt and repeat the installation process.
Hold the crankshaft pulley with the holding tool and handle. Tighten the crankshaft pulley bolt to 181 foot-pounds of torque. Install the rest of the parts in reverse order of removal.