General information
Top dead center (TDC) is the highest point of the piston stroke in its cylinder. Strictly speaking, in 4-stroke engines, during the rotation of the crankshaft, this position is reached by each of the pistons twice: once at the end of the compression stroke and the second time at the end of the exhaust stroke. When adjusting the valve timing and setting the ignition timing angle, in the vast majority of cases, the TDC position of the end of the piston compression stroke is used (usually the first cylinder).
The need to bring the piston to the TDC position arises when performing many procedures, in particular such as removing/installing camshafts, timing drive components and ignition distributor.
Some engines are designed in such a way that when the crankshaft or camshaft(s) is turned with the timing belt/chain removed, the valves may come into contact with the piston crowns, which carries the risk of damage to the corresponding internal components, including destruction of the cylinder head casting.
Do not allow the shaft position to change after removing the belt!
Procedure execution order
The arrangement of timing marks of the gear wheels of the camshaft (1) and crankshaft (2) in the TDC position of the end of the compression stroke of the piston of the first cylinder
Bringing any of the pistons to the TDC position is done by turning the engine crankshaft. If you look at the engine from the timing drive side, the normal direction of rotation of the crankshaft is clockwise. Remember that trying to turn the shaft counterclockwise can lead to a violation of the valve timing adjustments. The first is the cylinder, the outermost on the timing drive side.
1. Disconnect the negative battery cable. To make it easier to turn the engine, remove all spark plugs.
2. To gain access to the TDC mark on the camshaft gear, remove the timing belt cover (see Removal and installation the timing belt cover).
3. Using a wrench placed on the crankshaft pulley mounting bolt, turn the latter in the direction of normal rotation until the timing mark on the camshaft gear aligns with the corresponding mark on top of the rear timing belt cover. The mark on the rim of the crankshaft gear should align with the mark on the oil pump housing (see illustration The arrangement of timing marks of the gear wheels of the camshaft (1) and crankshaft (2) in the TDC position of the end of the compression stroke of the piston of the first cylinder).
When the listed conditions are met, the engine will be brought to the TDC position at the end of the compression stroke of the piston of the first cylinder.
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