It must be borne in mind that the failure of the timing belt (broken or sheared teeth) can lead to sticking of valves into pistons due to a mismatch of the angles of rotation of the crankshaft and camshafts and, as a result, to expensive engine repairs.
The surface of the toothed part of the belt must not have folds, cracks, undercutting of the teeth and delamination of the fabric from the rubber. The reverse side of the belt should not have wear, exposing the cord threads, and signs of burning.
On the end surfaces of the belt there should be no delaminations and fraying. If there is damage, the belt must be replaced.
The belt must also be replaced if traces of oil are found on it (before replacing the belt, the cause of its oiling must be eliminated) or when replacing a failed tensioner and belt support roller, coolant pump.
For clarity, we show most of the operations for checking the condition and replacing the timing belt on a dismantled engine.
Removing the air filter (see Removing the air filter).
To check the condition of the timing belt..
... we remove the hose for supplying coolant to the throttle assembly from the two holders of the upper front cover of the timing drive.
With the "10" head, we unscrew the three bolts securing the upper front cover of the timing drive.
Pressing the top..
... and two side (one on each side) cover latch..
...and take it off.
We turn on the fifth gear in the gearbox and hang out the right front wheel. Rotating the wheel clockwise, we turn the crankshaft and check the condition of the timing belt.
With proper belt tension..
... the movable roller pointer must match the fixed pointer on the tensioner bracket.
Timing belt tensioner: fixed pointer; bracket; eccentric roller; moving pointer.
If the movable pointer is displaced relative to the fixed one: - counterclockwise - the belt tension is not enough; - clockwise - the belt will be tightened.
In both cases, the belt tension must be adjusted (see below) Or replace the belt with a new one.
To replace the belt, remove the right front wheel and securely fix the car on a factory-made stand.
Remove the accessory drive belt (see Accessory drive belt replacement).
With the "17" head, we turn the crankshaft clockwise for the bolt securing the auxiliary drive pulley..
... until the alignment marks on the camshaft pulleys are aligned.
Loosen the accessory drive pulley bolt. To keep the crankshaft from turning, the assistant must engage fifth gear and depress the brake pedal.
We take out the bolt with the washer and remove the auxiliary drive pulley.
Once again, we check the coincidence of the installation marks on the camshaft pulleys. With correctly installed phases of the gas distribution mechanism..
... the mark on the crankshaft pulley should be located opposite the slot on the rear timing cover.
With the "10" head, we unscrew the three bolts securing the lower front timing cover..
... and remove the cover.
We substitute the emphasis under the engine crankcase pan and, having unscrewed the fastening bolts and nuts, remove the bracket of the right support of the power unit (see Replacing power unit supports).
To remove the belt from the pulleys, you need to reduce its tension. To do this, turn the coolant pump housing in the cylinder block seat counterclockwise while loosening the pump mounting screws.
Weaken the tightening of the three screws securing the coolant pump with a "5" hexagon.
To avoid leakage of coolant through the pump O-ring, loosen the screws only until the moment when the pump housing can be turned with a tool.
You can turn the pump with an open-end wrench "by 41" for the hexagon made on its body.
In the absence of such a key, we turn the pump housing..
... with sliding pliers for the hexagon..
... or with the help of a "12" open-end wrench and a wrench - by the rib on the pump housing.
Loosen the tension on the belt..
... remove it from the coolant pump pulleys, camshafts and crankshafts.
Before installing a new belt, check the condition of the coolant pump, tensioner roller and belt support roller.
When swinging and rotating by hand the pump pulley and rollers, there should be no play, jamming, or noise in the bearings. In the presence of these faults, we replace the damaged parts with new ones.
To replace the tensioner with the roller assembly, remove the bracket of the cylinder block, to which the bracket of the right support of the power unit is attached (see Removing the coolant pump).
With the "12" head, we unscrew the three bolts securing the tensioner to the cylinder block..
... and remove the belt tensioner.
With the "14" head, we unscrew the bolt of the support roller..
...and take it off.
We install the tensioner and the belt support roller in the reverse order. Tighten the bolts for fastening the tensioner and the support roller to the prescribed torques (see Tightening torques for critical threaded connections).
Before installing the belt, make sure that the alignment marks on the camshaft pulleys and the marks on the crankshaft pulley are aligned with the slot on the rear timing cover. In this position, we put the belt on the crankshaft pulley.
Pulling both branches of the belt, we start the front branch by the support roller, and the rear one, putting it on the coolant pump pulley, by the tensioner roller. We put the belt on the camshaft pulleys, eliminating the sagging of the belt branches.
We tighten the belt by turning the coolant pump clockwise until the movable and fixed pointers of the tensioner are aligned (see above). In this position, tighten the pump mounting screws.
With the fifth gear engaged, with the "32" head, we turn clockwise by the hub bearing fastening nut, the crankshaft two turns clockwise.
We check the belt tension and the coincidence of the alignment marks of the crankshaft and camshafts.
If the installation marks do not match, we repeat the operation to set the valve timing.
We make sure that there are no leaks from the coolant pump.
Otherwise, replace the sealing ring of the pump housing (see Removing the coolant pump).
If the valve timing is set correctly and the belt tension is normal, then install the lower front timing cover and the auxiliary drive pulley. Tighten the accessory drive pulley bolt to the prescribed torque (see Tightening torques for critical threaded connections).
Further assembly is carried out in the reverse order.