Timing belts are extremely difficult to successfully change unless you have experience in the area. The timing on the engine must be set exactly, or (unless non interference engine is present) the valves and the pistons would collide, which would cause call for very expensive engine repair.
i can explain you how to do it in 10 steps-
1.Disconnect the negative battery cable. Ensure you have your radio security code (if equipped) any preset radio stations and the time on a piece of paper to allow for quick resetting once repairs are made.
2.Remove the distributor cap, if so equipped. Most modern cars are "distributorless" electronic ignition types. They will have a cam (and crankshaft) position sensor instead. The important thing is to be able to determine "TDC" (Top Dead Center) on the #1 cylinder - techniques usually require consultation of the engine repair manual which all differs by model.
3.Using a wrench or socket on the crankshaft bolt rotate the engine until the timing mark on the crankshaft pulley is aligned with the 0° mark on the timing scale (This step assumes the timing belt is still intact). Under any circumstances do not do this on interference engines unless you are sure the belt is still in-tact. If you have not already bent your valves with a broken timing belt, you will likely do so if you spin the crankshaft without the camshaft spinning.
4.Verify the distributor rotor is aligned with the index mark on the distributor housing indicating the rotor is in position to fire the number one cylinder. If not, rotate the engine another full turn.
5.Remove any components or accessory drive belts that interfere with removing the timing belt cover. This varies by model; consult your service manual to determine which parts need to be removed from your vehicle. (This step involves removal of the crankshaft pulley, which may require a "pulley puller". See also comment below on special tools.)
6.Remove the bolts or screws holding the timing cover in place, and lift the cover off the engine. Some engines have a two-piece timing cover.
7.Check for proper alignment of the crank and camshaft timing marks. NOTE: Many engines have a dot or index line on the pulleys and/or sprockets that must be lined up with corresponding marks on the block, cylinder head, or accessory shaft. On some engines, the index mark on the camshaft sprocket aligns with the parting line of the first camshaft-bearing tower.
8.Check carefully the area around the belt for signs of oil leakage from the cam and crank seals, valve cover and oil pan. Check for coolant leaks from the water pump and water pump by-pass hose. Leaks must be repaired before the new belt is installed.
9.Loosen the timing belt tensioner.
10.Loosen the mounting bolt(s) holding the belt tensioner but do not remove it.
11.Pivot the spring loaded tensioner away from the belt and then retighten the mounting bolt(s)to hold the tensioner in the loose position.
12.Examine the tensioner pulley for damage such as dents or cracks.
13.Spin the tensioner pulley and listen for a rattle or humming noise that would indicate loose or worn bearings. Uneven wear at the rear of the old timing belt could indicate a misalignment between the tension pulley and timing belt due to worn bearings. If any indications of damage or worn bearings are found, replace the tensioner pulley.
Caution: The permanently lubricated tensioner pulley bearing can become dry, worn, loose, broken or can freeze up; so the best practice is to replace it, if it's not new!
14.With the tension on the timing belt relieved, the belt should slide easily off the sprockets. Timing belts that have been used for a long time may stick in the pulley grooves and require some gentle prying with a screwdriver to release.
15.When re-assembling, pay special attention to "torquing" specs on the engine manual, particularly the crankshaft pulley mounting bolt which usually has a very high torque spec.
16.If equipped with a hydraulic timing belt tensioner, removal may be required to compress the piston back into the cylinder. Place into a vise and compress until holes line up to allow the insertion of a holding pin. Once the pin is in place the tensioner can be re-installed.
i guess it was useful.
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