The Infiniti has several models, most of which have different procedures for replacing the timing belt. For the 1993 Infiniti J30, Infiniti recommends replacing the timing belt every 105,000 miles. The engine is an interference engine, which means that if the belt stretches past the scope of the tensioner, the valves will most likely hit the pistons and cause extensive engine damage. The job requires two special tools, available at any Infiniti dealership.
Place the drain pan under the radiator drain plug. Loosen or remove the drain plug and let the radiator drain. If you use a clean drain pan, you can reuse the coolant. Loosen the clamps on the air ducts with the appropriate socket or a screwdriver. Remove the air ducts.
Remove the radiator and radiator hoses. Remove the cooling fan and its coupling. Loosen the tensioners for the accessory drive belts to relieve the tension on the belts. Lift the belts off the pulleys.
Disconnect the negative battery cable and lay it to the side. Remove the wiring from the starter motor. Unbolt and remove the starter motor.
Remove the crankshaft pulley bolt. Remove the crankshaft pulley using the special puller. Remove the upper and lower timing belt covers.
Turn the crankshaft until the crankshaft sprocket timing marks line up. The dot on the sprocket lines up with the mark at the 4 o'clock position. Label the camshafts starting from the left, looking down at the engine, as C1, C2, C3 and C4. If the timing marks are not lined up on all the camshafts, turn the crankshaft one more time, and they will all line up. C1 and C2 timing marks are at 11 o'clock, and C3 and C4 timing marks are at the 1 o'clock position.
Screw the M6 x 0.63-inch bolt into the tensioner, thus locking the tensioner. Remove the tensioner securing nut and bolts, and the tensioner. Lift the timing belt off the sprockets and pulleys.
Remove the locking bolt from the tensioner. Compress the tensioner in a vise until the clearance between the arm and the casing is 0.16 inch. Reinstall the locking bolt to hold the arm inside the casing. Check that all five of the timing marks are still lined up.
Install the timing belt, working in a counterclockwise position, starting at the crankshaft, and making sure that the marks on the belt line up with the marks on the crankshaft sprocket. Work your way up behind the idler pulley, over C4 and C3, under the idler pulley between the cams, over the top of C2 and C1, then down behind the tensioner. Keep the timing belt taut on the right side of the engine, between the crankshaft and C4.
Count the teeth on the timing belt between the camshaft sprockets--there should be 24 teeth between the C2 and C3 and 59 teeth between C4 and the crankshaft sprocket.
Install the tensioner. Tighten the securing nut and bolts by hand. Push the tensioner against the timing belt. Turn the crankshaft clockwise 10 degrees. Tighten the tensioner securing nut and bolts to 13 foot-pounds of torque.
Turn the crankshaft counterclockwise 120 degrees. Loosen the tensioner securing nut and bolts. Push the tensioner away from the belt. Turn the crankshaft clockwise until the five timing marks are lined up.
Push the tensioner against the belt with a force of 13.2 pounds, using the push pull tool. Tighten the tensioner securing nut and bolts to 14 foot-pounds of torque. Turn the crankshaft clockwise 120 degrees. Turn the crankshaft counterclockwise 120 degrees until the timing marks line up again.
Push on the timing belt one-third of the way between C1 and the tensioner using a plate that measures 0.31 to 0.39 inches by 0.10 inches, with a force of 11 pounds. Measure the deflection. Repeat the procedure between C4 and the lower idler pulley. Measure the deflection (the distance the belt is pushed in). If the deflection is not between 0.24 and 0.28 inches, repeat the tensioning procedure (Step 10 through 13).
Ensure the tensioner securing nut is torqued to 14 foot-pounds of torque. Remove the tensioner locking bolt. Wait for five minutes. Check the clearance between the tensioner arm and the casing to ensure it is 0.16 inches. Check that the teeth in the belt are seated securely in the sprocket teeth. Install the rest of the parts in reverse order of removal.
Tighten the timing belt cover bolts to 30 inch-pounds of torque. Tighten the crankshaft pulley bolt to 165 foot-pounds of torque. Tighten the radiator drain plug. Refill the radiator.
