Signs of a defective cylinder head gasket are:
- loss of engine power.
- low coolant level, white exhaust smoke when the engine is hot.
- coolant in engine oil. The oil level does not decrease, but rather increases. Gray oil in the engine, foam on the oil dipstick. Oil liquefaction.
- engine oil in the coolant, oil loss.
- strong seepage of the coolant.
- lack of compression in two adjacent cylinders.
Withdrawal
Attention: Some works are described in more detail in the section "Removal and installation of the engine", therefore, it is recommended that you also read this section in advance. The description refers to the M20 engine. Additional instructions and tightening torques for M30 and M21 motors are given at the end of the section.
Remove the engine compartment hood.
Drain coolant
Disconnect the wires from the battery.
Disconnect the cables from the throttle lever. Unscrew bracket.
Disconnect the air intake hose.
Disconnect the air mass meter and idle air control connectors.
Disconnect the water hoses from the thermostat.
Mark with adhesive tape and disconnect fuel hoses.
If present, disconnect the connectors under the intake pipe and remove the hose.
Unbolt the engine wiring harness and set it aside.
Remove fan.
Disconnect the heater hose under the idle speed control, after releasing and pulling back the clamps.
Pull out the oil dipstick and unscrew the guide tube from the air manifold.
Remove toothed belt.
Disconnect heater hose from cylinder head.
Remove cylinder head cover.
Press down, overcoming the force of the spring, the crankcase ventilation tube under the intake manifold and fix it with the tool BMW-111290. For fixing, you can also use the appropriate metal or wire clip.
Remove cylinder head bolts in reverse order, i.e. from 14 to 1.
Attention. The cylinder head can also be bolted with Torx heads.
Remove cylinder head.
Attention: After removal, do not place the cylinder head on the contact surface, otherwise fully open valves may be damaged. Therefore, the cylinder head should be placed on 2 wooden blocks.
Installation
Before installing, clean the cylinder head and cylinder block from the remnants of the old seal. Do not allow seal residues to enter cylinder bores.
Close the cylinder bores with rags.
Measure the flatness of the cylinder head and engine block with a steel ruler in the longitudinal and transverse directions and, if necessary, mill (service station work). See Table 1.
Check the cylinder head for cracks and its running surfaces for scratches.
Thoroughly clean the holes for the cylinder head bolts from oil and other objects.
Attention: There must be no oil in the recesses, otherwise the bolts will not completely tighten the cylinder head, despite the fact that they are tightened to the required torque. In addition, the motor block may crack.
Be sure to replace the cylinder head gasket.
Apply a new gasket without sealing compound so that it does not block the holes.
Attention: With a milled cylinder head, a cylinder head gasket of normal thickness or 0.3 mm thicker, depending on the height of the modified cylinder head, can be installed. By installing a thicker gasket, a decrease in the volume of the combustion chambers is prevented.
Before installing the cylinder head, check that the camshaft is at top dead center.
Install the cylinder head. To guide the head, you can use 2 old cylinder head bolts, having previously cut their heads and cut through the slots for a screwdriver.
Be sure to replace and lightly lubricate the cylinder head bolts with engine oil.
Attention: On M20 engines, ordinary hex bolts could be installed, which must be replaced with bolts with hex socket heads.
Insert and hand tighten the cylinder head bolts lubricated with engine oil.
Caution: Be very careful when tightening the cylinder head bolts. Before tightening the bolts, check the accuracy of the torque wrench. In addition, a protractor, such as HAZET 6690, is required to tighten the cylinder head bolts. If a protractor is not available, place the key on the bolt head, attach a square to the key handle and mark the desired angle with chalk. Subsequently, turn the key handle in one pass to the line marked with chalk.
M20 engine (Torx cylinder head bolts)
(Pattern W - 1091)
- 1st pass: with a torque wrench until the tightening torque is 30 Nm.
- 2nd pass: 90°hard wrench (¼ turn).
- 3rd pass: 90°hard wrench.
Check the vent tube for damage or cracks and replace if necessary. Remove tool BMW-111209 and make sure that the tube returns to the correct starting position.
Install toothed belt.
Slide the heater hose onto the cylinder head and secure with a clamp.
Screw on the oil dipstick guide tube and insert the dipstick.
Install the heating hose.
Install the fan, making sure that the fan shroud is correctly positioned in the lower guide rails.
Install and screw the cable gland.
Connect the round connector, tighten the knurled nut.
Connect the water hoses to the thermostat housing and secure with clamps.
Install and tighten the V-belt.
Connect all water, fuel and vacuum hoses and secure with clamps.
Connect the electrical wires according to the markings made.
Connect the throttle cables, screw the bracket.
Screw the front muffler pipe to the exhaust manifold.
Install the cylinder head cover.
Install the engine compartment hood.
Connect the wires to the battery.
Fill with coolant.
Check engine oil level, top up if necessary. If the cylinder head was removed to replace a blown cylinder head gasket, it is recommended to change the oil with an oil filter change, as coolant may have entered the oil.
Caution: The cylinder head bolts must not be tightened.
M30 engine
Withdrawal
Unbolt intake manifold support.
See figure W - 1082
Unscrew the top cover 1 of the gear box. Additional details shown:
Remove the chain tensioner piston.
Unscrew the chain sprocket from the camshaft. At the same time, put the key and remove the bolts with light blows on the key handle.
See figure W - 1030
Insert locking pins 6 (BMW 111063), so that the rocker shafts do not rotate when the cylinder head bolts are loosened. Additional details shown:
- 1 spring
- 2 Washer
- 3 rocker
- 4 Distance ring
- 5 spacer ring
- A Exhaust rocker shaft
- E Inlet rocker shaft
Ansaugkrummer - intake manifold
Abgaskrummer - intake manifold
In sequence 14 to 1, first loosen the cylinder head bolts ½ turn and then back out.
1 Lid
6 Thread insert
7 Left spacer
8 Right gasket
9 Shaft seal
Installation
Attention: The cylinder head bolts are tightened in sequence from 1 to 14 in several passes:
- 1st pass: tighten bolts 1 to 6 to 60 Nm: remove locking pins tighten bolts 7 to 14 to 60 Nm. After that, wait 20 minutes.
- 2nd pass: tighten the bolts with a torque wrench to a torque of 80 Nm.
After 25 minutes of engine operation:
- 3rd pass: 35 degree hard wrench tightening.
Fasten the chain sprocket to the camshaft flange with a tightening torque of 7 Nm,
Attention: Apply the chain so that the centering pin on the sprocket is at the bottom left with the threaded holes vertical.
Install tensioner piston. In this case, tighten the M6 bolts with a tightening torque of 10 Nm, and the M8 bolts with a tightening torque of 22 Nm.
Screw on intake manifold support.
M21 engine
Withdrawal
Drain engine oil.
Remove expansion tank.
Remove turbocharger.
Remove the support from the air collector and loosen the fastening on the motor block.
Remove bracket from cylinder head.
Disconnect wires from glow plugs.
Open the oil separator.
Loosen the union nuts of the injection pipes on the injectors and remove the high pressure fuel pump. This requires a special key HAZET 4550.
Close the openings with protective caps.
Remove cylinder head cover.
Set the engine to top dead center. To do this, put the gearbox in neutral, tighten the handbrake. Turn the crankshaft pulley in the direction of engine rotation until the top dead center mark is opposite the notch on the toothed belt housing. In this case, the valves of cylinder 6 must intersect. Cylinders are numbered from 1 to 6 from front to back. The valves intersect when the camshaft is in such a position that both cams corresponding to cylinder 6 are facing up.
Lock the crankshaft at top dead center with an appropriate pin. To do this, insert the rod through the hole -arrow- in the engine block into the hole in the flywheel.
Unscrew the toothed belt cover, after removing the water hose.
Loosen the toothed belt tension and remove it from the camshaft pulley.
Loosen the camshaft sprocket bolt.
Loosen the tensioner nut and bolt.
(Drawing W 1097) In sequence 14 to 1, first loosen the cylinder head bolts ½ turn and then back out.
Installation
Install a new cylinder head gasket.
Attention: Depending on the height of the protrusions of the pistons above the surface, three gaskets of different thickness are installed. When replacing the gasket, pay attention to its marking and install a new gasket only with the same marking. Marking holes serve as markings for the gasket.
Check pistons and valves for wear and replace if required. If the signs of wear are small, then a thicker gasket is sufficient. To do this, you need to measure the protrusions of the pistons with a pointer indicator.
Cylinder head thickness:
- 1 hole thickness 1.55mm
- 2 holes thickness 1.68mm
- 3 holes thickness 1.87mm
Attention: The cylinder head bolts are tightened in sequence from 1 to 14 (Pattern W - 1097) in three passes:
- 1st pass: tightening the bolts with a torque wrench to a torque of 50 Nm
- 2nd pass: hard wrench tightening bolts 1 to 10 by 90°, bolts 11 to 14 by 73°.
After 15 minutes of engine operation:
- 3rd pass: 90 degree hard wrench tightening.
Adjust valve clearances.
Check the injection timing of the high pressure fuel pump.
Fit and tighten toothed belt.
Screw on the toothed belt guard without tightening the screws. Tighten the bolts only after installing the cylinder head cover.
Install the cylinder head cover.
Attention: Pull out the fixing rod.
Install fuel pipes, tighten cap nuts to 20 Nm. In case of leaks, tighten the nuts to 25 Nm.
Screw on the oil separator with a tightening torque of 17 Nm, having previously checked the integrity and, if necessary, replacing the sealing ring.
Screw bracket to cylinder head.
Screw the wires to the glow plugs.
Screw the support to the air collector and motor block.
Install turbocharger.
Install expansion tank.
Pour oil into the engine.