If the gap is too small, the valve timing changes, compression worsens, engine power decreases, the engine runs unevenly. In extreme cases, valves can be deformed or valve seats burned.
With increased clearances, strong mechanical knocks occur, the valve timing changes, due to a decrease in the valve opening time and thereby deterioration in cylinder filling, engine power decreases, the engine runs unevenly.
Valve clearance adjustment is only successful when there is sufficient valve sealing, there is no unacceptable play in the valve guide, and the ends of the valve stems are not broken.
The four-cylinder engines of the 318i and 318is since September 1987 and the 316i since September 1988 have hydraulic valve clearance compensators. They do not work on adjusting valve clearances.
Checking and adjusting valve clearances is carried out as part of the service every 20,000 km.
Checking and adjusting valve clearances can be done both on a cold and hot engine.
Examination
Remove air filter (see section «Removal and installation of the air filter»).
Remove cylinder head cover (see section «Removal and installation of a cover of a head of cylinders»).
Engage transmission in neutral (tighten the handbrake).
Turn the engine with a 27/30 mm wrench at the center bolt of the crankshaft pulley in the direction of engine rotation. At the same time, the camshaft also rotates.
Align the camshaft. that the cam be on the opposite side of the valve rocker to be checked; in this case, the generatrix of the cam is adjacent to the rocker arm.
It is advisable to start the test with the valves of the 1st cylinder located in front of the engine, setting this cylinder to the top dead center position. After that, the engine turns over (on a four-cylinder engine, half a turn) and check the valves of the next cylinder, according to the ignition sequence. Ignition sequence on a four-cylinder engine: 1-3-4-2; on a six-cylinder engine: 1-5-3-6-2-4.
Another option for adjusting valve clearances: engage 4th gear, release the handbrake. Move the car slightly until the cam moves away from one of the valves. The cam is set at an angle downwards. In this case, the cam does not press on the rocker (see drawing). In this position, measure the valve clearance and adjust if necessary.
Mark the rocker with a felt-tip pen.
Move the car a little more until another cam moves away from the rocker arm. In this case, the sequence of adjusting the valve clearances is indifferent. The rocker arms are marked so as not to double-check the valve clearance by mistake.
Petrol engines: Measure valve clearance with feeler gauge -F- inserted between eccentric -E- and end of valve stem.
Diesel engines models 324d, 324td: Measure valve clearance with feeler gauge -F- between cam and rocker arm.
The valve clearance is set correctly if the feeler gauge is tight.
For a sample, take a probe with an excess of a given size (see table) by 0.05 mm. The ohm must not go between the valve and the rocker arm. If it enters, reduce the valve clearance. Attention: The specified clearance values for intake and exhaust valves are the same.
«cold» the engine is called when the coolant temperature is below 35°C. When adjusting valve clearances to «warmed up» engine coolant temperature should be around 80°C. sign «heated» engine is the warm lower radiator water hose. The thermostat just opens a large coolant circuit.
Adjustment
If the valve clearance differs from the specified value, insert the BMW pin 113070 into the hole in the eccentric, loosen the nut -M- and turn the eccentric with the pin until the specified valve clearance is reached. If a BMW tool is not available, a thin screwdriver of the appropriate diameter can be used.
Tighten locknut to approx. 10 Nm (estimated value), while holding the eccentric.
Check the valve clearance again and crank the engine further.
In the same way, check or adjust the clearances of the remaining valves.
Install cylinder head cover (see section «Removal and installation of a cover of a head of cylinders)
Install air filter, see (chapter «Removal and installation of the air filter»).
Adjustment of the moment of the beginning of giving of the fuel pump of a high pressure on the diesel engine
The test requires a dial gauge with the appropriate adapter to be screwed into the pump.
Disconnect the ground wire from the battery.
Raise the front of the car.
Remove the middle plug on the high pressure fuel pump. Screw in an adapter instead of a plug (BMW 135330) and dial indicator and slightly tighten.
Turn the crankshaft clockwise towards the top dead center of cylinder 1 until the indicator needle shows the minimum value for some time. Turning should be 60-90°before top dead center. The piston of the 1st cylinder is in the position of top dead center when both of its cams of the 1st cylinder on the side of the toothed belt are facing upwards. To check, unscrew the oil filler cap and observe the camshaft.
To crank the engine, engage 5th gear, release the handbrake and move the vehicle or apply the handbrake and turn the crankshaft pulley with the key head on the central bolt.
Set dial indicator scale to «ABOUT».
Remove the plug from the motor block.
Turn the crankshaft until the support rod BMW 112300) will be able to enter the flywheel hole (top dead center position).
Attention: Do not turn the crankshaft against the direction of engine rotation. This will distort the measurements.
In this case, the indication of the pointer indicator should be 1.05±0.02 mm. Otherwise, adjust the high pressure fuel pump. On the 324d up to November 1988 (without DDE) the set value is 0.74+0.02mm.
Loosen the 2 rear bolts -3- without unscrewing them (the second bolt -3- is not visible in the figure).
Loosen nuts -1- and -2-.
Caution: Do not loosen the nuts too much to avoid changing the toothed belt tension.
Turn the high pressure fuel pump until the specified value on the dial indicator scale is reached.
Tighten nuts and bolts in sequence 1 - 3 to 25 Nm.
Check the adjustment again. To do this, remove the pin and first turn the crankshaft back 90°.
Remove dial gauge.
Screw in the central plug with a new gasket with a tightening torque of 15 Nm.
Caution: Remove the support rod from the engine flywheel. Put a stopper.
After the test drive, check the tightness of the central plug and, if necessary, tighten it to a maximum tightening torque of 20 Nm.