Warning: A removable toothed belt cannot be reinstalled and if it has just become loose, it must be replaced regardless of mileage.
Withdrawal
Remove engine compartment hood (see section «Removal and installation of a cowl of a motor compartment»).
Remove air filter (see section «Removal and installation of the air filter»).
Using a screwdriver, pry out the left and right expansion rivets, having previously knocked out the expansion pins.
Pull up the fan shroud.
Remove all spark plugs. To facilitate removal, a HAZET 1849 puller is available.
Remove cover -1- for ignition distributor. To do this, lift the left and right clamping bars with a screwdriver.
Move cable duct -2- up. To do this, insert a screwdriver into the slots (arrow).
Unscrew the cover of the ignition distributor and remove together with the ignition wires. This requires an 8mm bent key.
Unscrew the slider -4- of the ignition distributor and remove the trim ring -3-.
Remove V-belt from alternator. To do this, unscrew bolt -1- and nuts of bolts -2- and -3-. Turn bolt -3- in direction of arrow to loosen V-belt.
Loosen the water pump pulley. At the same time, tension the V-belt to keep the pulley from turning.
Unbolt vibration damper from crankshaft. At the same time, engage 1st gear, tighten the handbrake to keep the pulley from turning.
Drain coolant (see section «Coolant replacement»).
Unbolt thermostat housing under ignition distributor and set aside. Pull out the thermostat.
Loosen the 5 bolts securing the lower toothed belt cover. Remove cover.
Loosen the 4 screws securing the top toothed belt guard. Do not lose the centering bushings of the upper bolts.
Set cylinder 1 to top dead center (see section «Removal and installation of the distributor of ignition»).
Block the crankshaft at top dead center with a suitable pin. To do this, insert the rod through the hole (arrow) in the engine block into the flywheel hole.
Loosen the camshaft drive sprocket bolt without removing it. This requires a Torx key head.
Loosen tensioning roller nut -2-. Pull the tension roller inward, while unloading the toothed belt. Details shown in the figure: 1 - camshaft pulley; 3 - bypass roller; 5 - oil pump; 6 - oil pressure control valve; 7 - cover of the crankcase of the gas distribution mechanism.
Remove toothed belt.
Attention: With the toothed belt removed, do not change the position of the engine if possible.
Installation
Attention: When applying a toothed belt, the position of neither the distribution, nor the intermediate, nor the cranked ox should change. Failure to do so may result in severe engine damage or failure to develop full power. After tensioning the toothed belt, check the installation of the camshaft and crankshaft again.
Unscrew the cylinder head cover, pull out the camshaft cover.
Check that the camshaft is at top dead center. At the workshop, the camshaft is locked at top dead center using tool BMW 1131190. The camshaft is at top dead center when the lobes of cylinder 4 intersect. The intersection of the cams is their position, in which they are symmetrically turned to the left and right relative to the inclined engine.
Slightly (tightening torque 1-3 Nm) tighten the camshaft sprocket bolt. Turn the toothed pulley in the direction of rotation of the motor until it stops, so that the lug enters the recess.
Slightly tighten the nut of the tension roller so that it can still be moved.
Place the toothed belt with interference from the crankshaft toothed pulley on the tension roller.
Center the toothed belt on the camshaft pulley.
Set the scale of the toothed belt tension gauge to 0.
Place a measuring tool between the tensioning roller and the camshaft sprocket so that both outer rollers of the tool rest on the back of the toothed belt.
Turn the tensioning pulley to the left with a hexagon socket head wrench, thus tensioning the toothed belt. Specified value measured with BMW 112080: 32±2 scale divisions.
Tighten the tension roller to 22 Nm.
Tighten the camshaft sprocket to 60±5 Nm.
Install the camshaft cover and cylinder head cover.
Attention: Pull out the engine blocking rod.
Screw on the upper toothed belt cover, ensuring a secure fit of the bushings.
Screw on the lower toothed belt cover, after checking and, if necessary, replacing the gasket.
Insert the thermostat into its housing. Check the integrity of the O-ring and replace if necessary.
Screw on the thermostat housing.
Pour coolant into the cooling system, remove air from the cooling system (see section «Coolant replacement»).
Place the vibration damper on the crankshaft, while aligning the hole in the vibration damper exactly with the dowel pin. Tighten vibration damper mounting to 23 Nm.
Screw on the water pump pulley, while holding the pulley with a V-belt from turning.
Apply and tighten the V-belt (see section «Removing and installing alternator V-belt. V-belt replacement»).
Tighten nuts and bolts 1-3 in figure W-1056.
Insert the camshaft sprocket cover, while checking the integrity of the O-ring and. if necessary, replace the ring.
Tighten the ignition distributor.
Screw on the ignition distributor cap.
Insert the ignition wires into the insulator guides.
Insert the cable duct into the cylinder head cover.
Put on spark plugs.
Insert the fan shroud with the left and right strips into the holders. Insert spacer rivets from top left and right and drive plastic cores into them.
Install air filter (see section «Removal and installation of the air filter»).
Install engine compartment hood (see section «Removal and installation of a cowl of a motor compartment»).
Attention: If there is no adjusting and measuring tool (abroad, in an accident on the road), temporarily tighten the toothed belt so that between the tension roller and the camshaft toothed pulley, the belt can bend 5-10 mm. Belt tension should be checked at the earliest opportunity using a measuring device. Until then, avoid high engine speeds.