Pic. 109. Parts of the gas distribution mechanism drive of the 4A-F/FE engine. 1. Timing belt upper protective cover; 2 Middle toothed belt protective cover; 3. Bolt. 120 Nm; 4. Crankshaft pulley; 5 Lower toothed belt protective cover; 6. Tension roller; 7. Bolt. 37 Nm; 8. Toothed belt guide washer; 9. Camshaft gear; 10. Bolt. 47 Nm; 11. Tension spring; 12. Crankshaft gear.
Both overhead camshafts are driven via a timing belt and gears on each camshaft and on the crankshaft. The timing belt is connected only to the exhaust camshaft, through which the intake camshaft is driven using gears. The gear wheel on the shaft is located behind the crankshaft pulley. To tension the toothed belt, a movable tension roller is used. By moving the tension roller, the tension of the toothed belt is adjusted. Under normal operating conditions, there is no need to tighten the belt. If the belt is not damaged, it has a long service life, but it is generally accepted that it should be replaced after 100,000 km.
Belt tension must be adjusted if the belt is removed or replaced, or the tension roller is removed. The removed belt, if it is to be reinstalled, should not be exposed to oil or grease. It should also not be bent, otherwise it may be damaged.
Removal and installation
Although the work was described when disassembling the engine, it should be described additionally for the case when only the timing belt needs to be replaced. The drawings associated with the description have already been given on the previous pages. A general view of the mechanism drive is shown here.
- Unscrew the water pump pulley nuts, loosen the adjusting bolt or new belt and remove the V-belt (Pic. 5). Unscrew the water pump pulley.
- Remove four spark plugs. This requires an extended spark plug wrench, which should be inserted into the holes as shown in Figure 6.
- Disconnect the crankcase ventilation hose from the ventilation valve.
- Unscrew the three cylinder head cover nuts and remove the cover along with the nut spacer rings and gasket.
- Rotate the crankshaft pulley until the marks align with the mark "0" on the timing belt cover. Check that the valve tappets of the first cylinder have clearance. If this is not the case, turn the engine one more revolution. Figure 7 shows how the crankshaft pulley should be positioned at the TDC position of the engine.
- Unscrew the crankshaft pulley from the crankshaft and remove it from the shaft using a puller. The belt pulley has two threaded holes for installing a puller, as shown in Figure 8.
- Unscrew the upper, middle and lower timing belt covers and remove the gaskets. A total of 9 bolts need to be removed.
- Remove the timing belt guide washer. It is mounted on the front side of the crankshaft and can be easily removed as shown in Figure 9.
- If the timing belt will be installed again, mark it with an arrow for the direction of movement and a mark for the position of the camshaft and crankshaft gears, as can be seen in Figure 10.
- Loosen the toothed belt tensioner bolt at the front of the engine, press the tensioner to the left using a screwdriver, as shown in Figure 11, and tighten it in the new position. The timing belt is now free and can be removed. If desired, you can remove the belt tension roller.
- Remove the timing belt wheel from the crankshaft. If necessary, use a powerful screwdriver or pry bar for this.
- Loosen the camshaft gear bolt. To prevent the shaft from turning, it should be held. In the place shown in Figure 12 on the shaft there is a hexagon where you can install a wrench. Be careful not to damage the cylinder head when pressing the wrench into it. A belt with broken teeth must be replaced. Other defects include cracks, wear on the sides, or rounding of some or all of the teeth. In this case, the teeth of the gear wheels should also be checked. Hold the belt tensioner with one hand and turn the pulley with the other hand. Rubbing when turning the roller requires replacing the belt tensioner. When installing the timing belt, set the marks as described when removing the cylinder head. This also includes belt tension.