6-cylinder petrol engine
Note: this is a description of the removal and installation of the cylinder head of the M52 engine, which was installed on cars up to 8/97. Instructions for the M52TU engine installed from 9/97 are given at the end of the chapter.
A cylinder head gasket defect is identified by one or more of the following symptoms:
- Loss of power.
- Loss of coolant. White exhaust gases when the engine is warm.
- Oil loss.
- The presence of coolant in the engine oil, the oil level does not decrease, but it becomes less.
- Gray color of engine oil, foamy emulsion on the oil level indicator, liquid oil.
- Engine oil in coolant.
Attention: In this case, after the repair, it is necessary to remove the radiator and wash it with a BMW cleaning agent to remove oil residues.
The coolant boils a lot.
There is no compression in two adjacent cylinders.
Withdrawal
Only remove the cylinder head from a cold engine. Do not remove the exhaust and intake manifolds from the head.
Disconnect ground wire (-) battery. The battery is located in the luggage compartment behind the right side trim.
Attention: This erases the contents of memory devices, such as the engine trouble code memory. Follow the instructions given in the chapter "Removing and installing the battery".
Raise the car.
Unscrew the front exhaust pipe from the exhaust manifold, see p. 66.
Drain the coolant, see handed out "Maintenance work".
Drain the engine coolant by unscrewing the drain plug on the side of the cylinder block under the exhaust manifold. After draining, immediately screw the plug back into place and tighten.
Loosen the clamps and remove the coolant hoses from the thermostat.
Remove spark plugs, see section "Maintenance work".
Remove intake manifold.
Compress the wire stoppers and disconnect the plug connectors:
- 1 - temperature sensor,
- 2 - remote thermometer,
- 3 - hydraulic switch,
- 4 - valves for regulating the speed of the crankshaft at idle.
Release screws on cylinder head cover -arrows-. Pay attention to the location of the rubber pads under the bolts for subsequent assembly.
Remove the side clips and remove the wiring conduit from the thermostat housing.
Remove the intake camshaft cover.
Unbolt engine lifting eye -arrows-.
Place the engine crankshaft in a position in which the piston of cylinder 1 is at TDC, while the tops of the intake and exhaust camshafts for cylinder 1 (from the side of the camshaft drive chain) should be equally directed upwards. The arrows on the sprockets of both camshafts must point upwards. Turning the crankshaft can be done in different ways:
- shift into 5th gear and drive the vehicle forward on level ground, or
- turn the crankshaft belt pulley with a socket wrench at the central mounting bolt in the direction of rotation (with neutral gear engaged.
Lock engine crankshaft at cylinder 1 TDC with special tool BMW 112 300 or other suitable pin. To do this, remove the plug and insert the pin through the hole in the cylinder block into the hole in the flywheel.
Unscrew the oil line from the VANOS actuator and close the holes with clean plugs.
Disconnect the electrical connector from the VANOS actuator solenoid valve.
Unscrew the pins.
Lock the camshafts in the TDC position for cylinder 1 with the BMW tool shown in the figure.
Caution: Do not damage the camshaft housing when doing this. If necessary, mill the key to make it narrower.
If at the same time the camshafts must be turned so that the valves of cylinders 1 and 8 begin to move, then the crankshaft must first be turned from the TDC position in the direction of rotation by about 30°and only after turning the camshafts return it back. This avoids contact between valves and pistons.
Unscrew the plugs from the actuator housing.
Loosen the exhaust camshaft sprocket bolts.
Press the upper chain tensioner downwards and lock in this position with the special tool from BMW.
Loosen nuts and remove cover.
Remove the VANOS actuator while turning the sprockets to the right as far as they will go. If the sprockets do not turn by hand due to the installed cup spring, to increase the turning force, attach a special tool from BMW to one sprocket, as shown in the figure.
Loosen the cylinder identification sensor. Disconnect the sensor connector.
Loosen the intake camshaft sprocket mounting bolts. Remove the shim from the sprocket.
Remove both sprockets along with the chain from the camshafts.
Remove the upper chain tensioner support bracket.
Unscrew the chain tensioner at the cylinder head.
Attention: Hold the tensioner as it is under the influence of the spring.
Remove the chain guide and then the sprocket from the exhaust camshaft.
Attention: Support the chain against slipping down with a wire hook.
Installation
Before installation, clean the contact surfaces of the head and cylinder block with a conventional seal remover and a suitable wooden scraper. Make sure that the remains of the seal do not get into the holes, for which the holes are closed with rags.
Thoroughly clean the holes of the cylinder block for the cylinder head bolts of oil and other deposits using compressed air or a rag wound around a thin screwdriver.
Attention: There must be no oil in the blind holes, otherwise the bolts cannot press the cylinder head with the required force, although they will be tightened to the prescribed torque. In addition, the cylinder block may crack in this case.
Check guide bushings -arrows- in cylinder block for damage and correct installation. The bushings serve to center the cylinder head.
Check the cylinder head for cracks, make sure that there are no marks on the working surface of the cylinders.
Check the cylinder head and cylinder block for lack of straightness in the longitudinal and transverse directions using a steel ruler. Finish parts if necessary (workshop work). The maximum allowable non-straightness is 0.03 mm.
Attention: In the case of a machined cylinder head, depending on the height of the head obtained after machining, a sealing gasket of both normal and increased thickness, which is 0.3 mm more than usual, can be installed. A thicker gasket avoids a decrease in the volume of the combustion chamber.
Seal the transitions to the cover of the sprocket niche with Drei Bond 1209 sealant that retains elasticity for a long time.
Be sure to lure the cylinder head gasket. Lay the cylinder head gasket flat and on a dry surface of the cylinder block so that the holes in the cylinder head and cylinder block do not close.
The camshafts must be fixed in the correct position using the BMW tool shown in picture W-1030B.
Together with an assistant, attach the cylinder head, avoiding its distortion, because. otherwise the new gasket will be damaged.
Caution: Always use new cylinder head bolts. New parade bolts are easy to lubricate with engine oil. The washers for the bolt heads of the serial cylinder head do not fall out, because they are underlined. When installing a new cylinder head, insert new washers by caulking.
Tighten the cylinder head bolts in sequence from 1 to 14 in three stages:
- Reception 1: using a torque wrench with a torque of 40 Nm.
- Reception 2. Using the locked wrench, tighten by an angle of 90°.
- Technique 3: Using the locked wrench, tighten by 90°.
Caution: Cylinder head bolts must be tightened very carefully. The torque wrench must be checked for accuracy before tightening. In addition, a protractor, for example, HAZET 6690, is required to tighten the cylinder head bolts. If there is no protractor, a torque wrench is put on the bolt head, a ruler with a right angle is attached to the key lever and a mark is made small on the cylinder head corresponding to turning the key by 90°. Then, with one effort, turn the key handle until it is aligned with the marked mark.
Tighten the sprocket bay cover bolts.
Slide the sprocket onto the camshaft flange. The arrow on the asterisk should point up. The threaded holes on the camshaft flange must be located on the left side of the longitudinal slots for the bolts on the sprocket, since when installing the chain tensioner, the sprocket turns to the left.
Install the chain guide and upper chain tensioner.
Screw the BMW special tool 11 4220 into the threaded hole -1- for the chain tensioner.
This tool presses on the camshaft drive chain and is pre-tensioned so that the threaded holes on the shaft flanges are located in the middle of the longitudinal slots in the sprockets. With some skill, a similar device can be made independently. Without a tool, correct installation of the camshaft drive chain is not possible.
Install the shim on the intake camshaft and tighten to 20 Nm.
Slide the sprockets onto the camshaft flanges together with the upper camshaft drive chain. The flat side of the intake camshaft sprocket should face outward and its shoulder should face the camshaft.
The arrow on the exhaust camshaft sprocket points up. The sprocket mounting bolts must be located in the middle of the longitudinal slots in the sprocket.
Variation of cup spring bases: Place shim -3- on intake camshaft sprocket and tighten to 20 Nm.
Belleville version: Fit shim to intake camshaft sprocket (about 2 mm thick), then install disc spring -2-.
Attention. Ensure the correct mounting position of the Belleville spring. The larger diameter spring should be against the camshaft sprocket. After that, install the adjusting washer (about 4 mm thick). Apply an anti-tightening agent to 3 fastening nuts and tighten the nuts to a torque of 20 Nm.
Screw on the exhaust camshaft sprocket, but do not overtighten the bolts.
Before installing the VANOS actuator, turn both sprockets as far as they will go (as far as the longitudinal slots in the sprockets allow) to the right.
Before installing the VANOS actuator, press its splined shaft with hydraulic piston -1- into the actuator housing -2- as far as it will go.
Make sure guide bushings -1- are in correct position. Seal the corner joints of the sealing surfaces between the mechanism case and the cylinder head with Drei Bond 1209 liquid sealant.
Insert the VANOS actuator so that the splined shaft of the actuator engages in the sprocket. To secure the sprocket by hand (and in the version with a disc spring - with the help of a tool) turn counterclockwise.
Attention: Fixation must be done with the first tooth, otherwise the valve timing will be shifted.
Slide the VAIMOS actuator towards the cylinder head, the sprocket turns to the left due to the helical gearing. Use your hand to help the star turn.
Tighten nuts for VANOS actuator.
Remove special tool 11 3 292 to relieve upper chain tensioner, see "Withdrawal".
Tighten the camshaft timing chain tensioner by turning the tensioning bolt of the special tool to 1.3 Nm.
In this position, tighten the exhaust camshaft sprocket evenly in 3 steps in a diagonal pattern to 20 Nm.
Remove special devices for locking camshafts and pre-tensioning their drive chain.
Attention: The BMW workshop then checks the functioning of the VANOS system using a special tool. If after installing the VANOS system there is no deterioration in the dynamic properties of the vehicle, the test can be omitted, otherwise contact a BMW workshop.
Screw the oil line with a new seal to the VANOS actuator housing. Connect electrical plug.
Screw in the lower chain tensioner with a new O-ring and tighten to 35 Nm. Pay attention to the position of the groove on the tensioner piston during installation: the groove must be vertical to the tensioner bar. Unload upper chain tensioner when installing.
Install the sprocket housing cover with a new seal. In this case, tighten the M6 bolts to a torque of 10 Nm, and the M8 bolts to a torque of 22 Nm. Don't forget the guide bushings on both outer bolts.
Screw in 3 studs to secure the cylinder head cover.
Install the cylinder head cover. Replace damaged gaskets, see illustration. When applying the outer sealing gasket of the cylinder head cover, pay special attention to the correct installation of the gasket in the recesses of the cylinder head from its end face. Tighten cover bolts evenly to 10 Nm.
Insert and screw on the cylinder identification sensor. If the O-ring is damaged, it must be replaced with a new one.
Install spark plugs, see section "Maintenance work".
Install the intake manifold, see p. 10.
Connect electrical wires, see "Withdrawal".
Screw the front exhaust pipe with a new gasket to the exhaust manifold, see p. 66.
Attention: Before starting the engine, remove the locking pin from the hole in the flywheel.
Fill with coolant.
Check engine oil level, top up if necessary. In the event that the cylinder head was removed due to a defective gasket, it is recommended to change the oil and oil filter, as there may be coolant in the engine oil.