Note: this describes the removal and installation of the M51S engine head (model 525tds) Instructions for the M47 engine model 520d are given at the end of the chapter.
Cylinder head gasket defect is determined by one or more features.
Withdrawal
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 directions given in the pave "Removing and installing the battery".
Drain into a container and save the coolant.
Release the clamp and disconnect the coolant hose coming from the radiator from the thermostat housing.
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.
unscrew the mount (left hand thread) And remove viscous fan.
Remove the engine covers from the intake manifold.
Loosen the intake manifold brackets and remove them.
Detach the following hoses from the holder on the cylinder head:
- 1 - brake booster vacuum hose,
- 2 - coolant hose for heater,
- 3 - fuel line to the high pressure fuel pump (injection pump).
Remove the vacuum hose from the intake port (at the exhaust gas recirculation valve).
Press the locking wire downwards and disconnect the electrical plug of the temperature sensor at the intake manifold.
Unbolt the exhaust gas recirculation pipe to the intake manifold.
Release the clamp and disconnect the air supply hose from the intake manifold.
Loosen intake manifold mount.
Loosen the union nuts of the high pressure fuel lines at the injectors and at the injection pump. This requires a special key from BMW or HAZET4550. Close all openings on fuel lines, injectors and injection pump with protective caps.
Loosen plug connectors and remove glow plug caps.
Disconnect the plug connector of the injector needle lift sensor.
Unfasten the EGR pipe to the exhaust manifold and retainer and remove the pipe.
Remove V-ribbed belt.
Unbolt the turbocharger to the exhaust manifold.
Loosen all cylinder head cover bolts uniformly, first by ½ turn, and then fully align. Remove cylinder head cover.
Loosen the hydraulic V-belt tensioner and remove the damper.
Attention: The removed tensioner must only be stored in the installation position, i.e. vertically, otherwise malfunctions may occur later in its operation.
Remove bolts -1- and -2- and remove vacuum pump. The bolt -2- is also a support for the camshaft drive chain guide rail. Since the bolt thread must be tight, a new bolt must be screwed in. After each release, the bolt must either be replaced with a new one or lubricated with a conventional liquid sealant before screwing.
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 in this position with BMW special tool 11 2 300 or other suitable pin. To do this, insert the pin through the hole in the cylinder block into the hole in the flywheel. If available, first remove the plug from the cylinder block bore.
Caution: Do not turn the crankshaft and camshaft again after removing the cylinder head.
Distribution led to stop with a device from BMW. The adaptation is not absolutely necessary, since when releasing the sprocket holder, you can hold the camshaft by the hexagon with a SW 27 key.
Attach a suitable lever to the chain tensioner bar and press it out.
Unscrew the plug and fix the tensioner in the depressed state with a suitable pin.
Holding the camshaft by the hexagon wrench SW 27, unscrew the fastener and remove the camshaft sprocket. Hold the chain against slipping down with a wire hook.
Unscrew the support pin of the tensioner bar from the cylinder head and remove it together with the sealing ring.
Unscrew the support pin of the guide bar and remove it together with the O-ring.
Loosen the fastening of the sprocket niche cover. Fastening -1- is made in the form of a stud with a nut.
Loosen bolt -arrow- and remove leaking fuel hose from injector.
Loosen the cylinder head bolts ½ turn in the sequence from 14 to 1. Then unscrew the bolts in the same sequence. Removing the bolts requires an E12 socket for male bolts.
Remove the cylinder head.
Attention: The cylinder head must not be placed directly on the worktable with the sealing surface, as the fully open valves may be damaged. Therefore, the cylinder head should be placed on 2 wooden stands.
Installation
Before installing, clean the cylinder head and cylinder block to remove seal residues with a suitable scraper. Make sure that the seal residues do not get into the holes, for which the holes are covered with rags.
Check the cylinder head and cylinder block for longitudinal and transverse straightness using a straightedge.
Warning: Cylinder head finishing is not permitted. Replace the cylinder head if it is not straight.
Check correct seating of guide bushings -arrows-. The bushings serve to center the gasket and the cylinder head.
Check that there is no oil or other deposits in the holes of the cylinder block for the cylinder head bolts - if there is, then remove it. If compressed air is not available, wrap a cloth around the screwdriver and wipe the holes dirty.
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.
Always replace the sealing gasket and cylinder head bolts with new ones.
Lay a new cylinder head gasket dry and on a dry surface so that the bores in the cylinder head and cylinder block do not close. The sealing gasket, depending on the thickness, is marked with a different number of holes. The new gasket must be the same thickness (with the same number of holes), which is the removed gasket.
If it is not clear how thick a new gasket should be, for example after an engine block has been repaired, the protrusion of the pistons from the cylinder block must be measured using a linear displacement indicator. The gasket thickness is selected according to the maximum protrusion of the pistons of all six cylinders. For measurement, set the indicator at point -A- and by slightly turning the crankshaft clockwise and counterclockwise determine the maximum protrusion of the piston from the cylinder block. Repeat measurement at point -B-. The piston protrusion is taken as the average value determined from the results of measurements at points -A- and B-. Carry out similar measurements of the protrusion of the pistons of the remaining cylinders.
Based on the obtained values, the average value of the protrusion of the pistons is determined. To do this, the values obtained are added together and the sum divided by B. If the average protrusion of the pistons is less than 0.76 mm, a seal with two marking holes must be used. If the protrusion is 0.76 mm or more, a three-hole gasket is installed.
Attention: If one or more cylinders have a piston protrusion of more than 0.81 mm, a three-hole gasket must be used anyway.
Only for version with injection pump bracket: Replace shaped rubber seal. Clean the seal groove. Seal the groove ends with Drei Bond 1209.
Seal the gaps in the joints between the cover of the sprocket niche and the cylinder head with Drei Bond 1209 sealant.
Put the cylinder head together with the assistant on the cylinder block without allowing it to be skewed, otherwise the seal is damaged.
Attention: The camshaft and crankshaft must not be turned after removing the cylinder head, as the open valves will rest against the piston. If the shafts did turn, they must be placed in the correct position before installing the cylinder head, see Fig. "Withdrawal". The figure shows the high pressure fuel pump drive sprocket of a diesel engine. The star mark must be facing up.
New cylinder head bolts are easy to lubricate with engine oil and tighten by hand.
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. Or, put a torque wrench on the head of the bolt so that the wrench handle is located along the cylinder head, measure a 90°angle with a goniometer and make a mark on the cylinder head with chalk.
New cylinder head bolts are tightened in 6 steps. In each step, the bolts are tightened respectively in sequence from 1 to 14.
- Reception 1: using a torque wrench, tighten the bolts to a torque of BO Nm.
- Technique 2: Using the locked key, loosen the bolts again by 180° (½ turn).
- Reception 3: Using a torque wrench, tighten the bolts to 50 Nm.
- Technique 4: turn 90°using the locked key (¼ turn).
- Technique 5: Using a locked wrench, turn 90° (¼ turn).
- After warming up the engine for 25 minutes (after engine assembly): Technique 6: turn 90°with the locked key.
Fit the sprocket housing cover and tighten the fastening bolts to 10 Nm.
Tighten the fastener next to the injector and put on the injector hose to drain the leaked fuel, see picture W-10254 above.
Screw in 2 support pins with new O-rings for tensioner and guide films.
Screw the sprocket with the applied chain to the camshaft, do not overtighten the mounting bolt.
Caution: The contact surfaces of the mating parts must be free of grease and must be clean.
Remove the chain tensioner fixing pin to tension the chain. Screw the plug into the cylinder head into the locking pin hole.
Only when the camshaft is fixed with a BMW adjusting gauge: The gauge is designed to adjust chains up to approx. 20,000 km.
For chains with higher mileage, it is necessary to install a gasket on the intake side of the cylinder head (calibrated plate) thickness A = 4.5 mm. If no gauge is used, turn the camshaft 2°to the left and hold it in this position by the hexagon with a SW 27 wrench.
In this position, tighten the camshaft sprocket in 2 steps:
- Reception 1: Using a torque wrench, tighten the bolt to 20 Nm.
- Technique 2: Using the locked wrench, turn 35°further.
Caution: Remove the crankshaft locking pin from the hole in the flywheel and the camshaft locking tool. Turn the engine crankshaft several times by hand and check the valve timing.
Insert the vacuum pump with a new O-ring so that the pump driver fits into the sprocket notch on the camshaft.
Attention: The slotted head bolt for fastening the sprocket has a hole for supplying lubricant to the vacuum pump. Clean the hole from dirt.
Tighten the 2 screws securing the vacuum pump to 20 Nm. Either replace the inner bolt with a new one, or lubricate with liquid sealant before screwing in to ensure the tightness of the threaded connection.
Attach damper and V-ribbed belt tensioner bracket and screw them down.
Install poly V-belt.
Check the sealing gasket of the cylinder head cover for damage, replace the gasket if necessary.
Attach the cylinder head cover and tighten the mounting bolts in a crosswise manner in the sequence "from inside - outside" torque 15 Nm. Before tightening the bolts, pay attention to the incorrect position of the gasket in the recess in the cylinder head, see illustration.
Screw turbocharger with new gasket to exhaust manifold with new self-locking nuts. Lubricate bolts with high temperature grease. Tighten all bolts to 45 Nm.
Connect plug connectors for glow plugs.
Connect the plug to the injector needle lift sensor connector.
Attach the high pressure fuel lines, do not kink the fuel lines. Tighten the union nuts on the injector fittings and high pressure pump with a special wrench to a torque of 20 Nm.
Replace the intake manifold seals. Then attach the collector and tighten the fastening in a cross way to a torque of 25 Nm.
Tighten the intake manifold mounting bolts.
Route all hoses in the intake manifold holder and connect them, refer to "Withdrawal".
Tighten the EGR pipe to the exhaust manifold, screw on the retainer and the intake pipe.
Connect electrical wires.
Connect the mass wire of the battery, set the clock, tune the radio to transmitting radio stations.
Connect the coolant hose from the radiator to the thermostat housing and secure the hose with a clamp.
Fill with coolant.
screw viscous fan (left hand thread).
Check engine oil level, top up if necessary. If 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.
Attention: Warm up the engine for 25 minutes. Remove the cylinder head cover and turn the cylinder head bolts 90°in the direction of tightening using the locked wrench in the sequence shown above in fig. W-1097.
For accurate tightening of the cylinder head bolts, a protractor, for example, HAZET 6690 is required. Alternatively, a torque wrench is put on the bolt head like this. so that the key handle is located along the cylinder head, measure an angle of 90°with a goniometer and make a mark on the cylinder head with chalk.
Attach the cylinder head cover and tighten the mounting bolts in a crosswise manner in the sequence "from inside - outside" torque 15 Nm.
Install the engine cover.