Engine Maintenance: Timing Belt Replacement on Lexus GS 300s - Page 2 of 2

Engine Maintenance: Timing Belt Replacement on Lexus GS 300s

Recommended replacement intervals for timing belts are all over the map these days. Mileage and time suggestions can vary widely, so examine accessory belts and factor in the use of the car and its maintenance history. In this article, we'll discuss timing belt replacement on a 2001 Lexus GS 300 model with the 2JZ-GE engine.

Once the main timing marks are located and aligned, turn the crankshaft counterclockwise to align the sub-timing marks (see Photo 5) with the same reference points used for the main timing marks. At this point, if you were planning on reusing the timing belt for some unusual reason, put an arrow on it to indicate the direction of travel. You could also paint reference marks on the belt to speed reinstallation.

While again holding the crankshaft pulley, remove the retaining bolt. A pulley puller may be necessary to remove the pulley without moving the crankshaft. Then remove the lower number 1 timing cover (see Photo 6). Loosen the tensioner (damper) bolts evenly and take the tension off the belt. Remove the outer belt guide (concave side goes out), and the little finger retainer that restricts movement of the belt away from the crank sprocket at the lower right side (5 o’clock position). Then remove the belt after marking the belt and sprocket, if you’re reusing the belt.

INSPECTION
As with all timing belt replacement procedures, inspect for damage to or from the belt, oil leaks or mechanical problems (loose parts) that would shorten the life of the replacement belt. Also, inspect the old belt for cracks, uneven wear, oil or coolant saturation, or impact wear from the guides or foreign objects that might have made their way into the covers. Inspect the tensioner damper for oil leakage that would reduce the tension that it applies.

photo 5: turn the crankshaft counterclockwise to align the sub-timing marks.A small amount of oil may be present at the seal, but nothing more than a little seepage is acceptable. If you can depress the push rod into the housing by hand, replace the tensioner. If the rod does not stick out of the body at least 8.0 to 8.8 mm, replace it. Make sure the tensioner pulley spins freely and that the retaining bolt is tight. Specifications call for Loctite on the retaining bolt and torquing to the proper specification. The pulley bracket should move freely; if not, make sure the spacer washer is in place between the bracket and the engine block on the retaining bolt.

If the camshaft pulleys need to be removed for seal replacement, be aware that to remove the intake variable timing pulley, only the center bolt should be removed. Do not loosen the five bolts that hold the timing mechanism together. If there is any sign of oil leakage at the variable timing sprocket (not the camshaft seal), then the variable timing pulley may need to be replaced. Variable valve timing codes may indicate leakage or other component failure.

photo 6: you may need a puller to get the pulley off without moving the crankshaft.Service bulletins and tech assistance reports indicate that the crankshaft sprocket can be easily damaged, and cause timing and driveability problems and codes. There are reports of even small scratches on the reluctor wheel causing problems as well as missing teeth.

The standard procedure for hydraulic damper retraction is used to depress and pin the damper push rod in a vise or press. Make sure even and straight pressure are applied, and install a 1.5 mm hex wrench or pin to hold the pushrod in the retracted position. The engine should be cold by this time; if not, take a break until it is so the proper tension can be put on the new belt.

BELT INSTALLATION
Photo 7: Make sure the crankshaft is aligned with the mark on the oil pump housing. The crankshaft shouldn’t have moved from its proper position, but double-check and adjust the timing mark alignment on the crank sprocket and the oil pump housing, if necessary (see Photo 7).

Make sure the front of the engine is clean and dry, and slide the new belt onto the crankshaft sprocket and over the idler/tensioner pulley. If you are reusing an old belt, make sure that you have reinstalled it in the same position and direction. Install the little restrictor to hold the belt onto the crank sprocket. Install the lower belt guide onto the crankshaft and install the number 1 timing cover.

Install the crankshaft pulley and make sure that the crankshaft sub-timing mark is still aligned with the “O” on the cover. Install the pulley retaining bolt hand tight (do not move the crankshaft). Recheck the timing marks on the camshafts and adjust if necessary, remembering that the camshaft sub-timing marks should be the ones that are lined up with the marks on the number 4 cover (inner timing cover). Slide the timing belt onto the camshaft sprockets with slack on the tensioner side and no slack between the camshaft sprockets. Install the tensioner damper by alternately tightening the bolts after making sure the dust boot is in position.

Remove the hex wrench or pin from the tensioner body and allow a few minutes for the tensioner to stabilize pressure on the belt. After checking that all the proper timing marks are aligned, turn the engine over by hand, clockwise only, at least two full turns and recheck timing mark alignment. There should not be any restrictions, except the compression of the engine. If it wasn’t such a chore, having the spark plugs out makes this step easier and more conclusive that there is no valve-to-piston contact. If the timing marks are off, redo the procedure rather than take the chance that a mistake was made. Having the marks color-coded makes verifying proper timing easier.

Tighten the crankshaft pulley bolt to the proper torque and reinstall all removed accessories, covers, radiator and fans. Use a vacuum-type cooling system filler to prevent air locks and overheating (not good for a new belt).

FINISHING UP
Even if you haven’t seen or serviced one of these cars yet, they are going to be around for a long time, like most Toyota products. Being prepared for routine maintenance and the peculiarities of the engine and drivetrain will put you ahead of the game when service opportunities come along. These Lexus models are superbly comfortable, extremely well made and performance is on par with the competition.

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