Make sure that the blind holes in the cylinder block are clean, paying particular attention to the absence of traces of oil on their bottom, since the compression of oil when tightening the mounting bolts can lead to cracks in the cylinder block.
Install the cylinder head gasket (its installation is possible only in one position). Lubricate the front of the gasket (from the timing drive side) sealant such as Curil or Atmosit.
Note. On the "520i" model, a cylinder head gasket with a reinforced metal lining is used. It can be used for BMW "518" and "520" carburetor engines, but the reverse replacement is not possible.
When installing the camshaft, its flange must be in the following position:
- models "518" and "520": the hole in the dowel pin must be facing downwards and the groove in the upper part must match the lug on the cylinder head (see photo);
- models "525" and "528": the dowel pin on the flange should be at an angle of about 45° downwards and to the left. The upper threaded hole of the flange should be against the lug on the cylinder head (see photo).
In both cases, the piston of the 1st cylinder (counting from the timing mechanism drive) should be at TDC. The mark on the lower cover of the timing mechanism drive should be opposite the second mark on the crankshaft pulley.
Install the cylinder head and gradually tighten its mounting bolts in three stages in the specified order to torques of 3.5-4.5 kgf·m and 6.0-6.5 kgf·m.
Install the camshaft sprocket with the chain on it, aligning the holes for the sprocket mounting bolts on the sprocket and flange. Tighten the camshaft sprocket mounting bolts and lock them by bending the locking plates.
Install the upper timing cover, plunger and chain tensioner spring; in this case, the plunger head should enter the tensioner body until it stops.
Adjust the valve clearances.
Set the ignition timing (see here or here).
Further installation of the cylinder head is carried out in the reverse order of removal.
Fill the cooling system with fluid, start the engine and check for leaks.
Since model year 1978, installation of cylinder head for BMW engines "525", "528" and "528i" is performed taking into account the following:
- on the "528i", attach the clamp for the hose going to the metering unit so that the mounting screw is on the throttle switch side;
- when installing hoses 15 and 16 of the interior heater, do not swap them - hose 15 is connected to the drain line at the top, and hose 16, coming from the cylinder head, is at the bottom.
On BMW "520" and "520i" with 6-cylinder engine, installation of the cylinder head is carried out in the reverse order of removal, taking into account the following:
- clean the cylinder head mounting bolts and lightly lubricate their threads with engine oil;
- make sure there is no oil in the blind holes of the cylinder block;
- tighten the head mounting bolts to the specified torques in the order shown in the photo, in three steps,
- check the condition of the expansion tube sealing rings and replace them if necessary;
- make sure that the piston of the 1st cylinder, the camshaft and the distributor are in the TDC position;
- install the timing belt and adjust its tension;
- make sure the camshaft is in the correct position;
- install the timing belt cover while securing the engine lifting eye;
- install the TDC sensor, ensuring a gap of 0.2-2.0 mm between its end and the torsional vibration damper;
- install the generator and adjust the tension of the V-belt of its drive. The normal deflection of the belt when pressed with the thumb should be 5-10 mm;
- adjust the valve clearance and install the cylinder head cover with a new gasket;
- adjust engine idle speed;
- after 1000 km of running, tighten the cylinder head mounting bolts. Do not loosen the cylinder head mounting bolts under any circumstances.
Replacing the cylinder head gasket on the "520" and "520i" with a 6-cylinder engine
Remove the cylinder head.
Thoroughly clean the mating surfaces of the cylinder head and cylinder block.
Check the flatness of the mating surface of the cylinder head and, if necessary, grind it.
Install a new head gasket, making sure it is correctly positioned over the coolant passage holes
Turn the camshaft 1-2 turns counterclockwise to the crankshaft using a 1/2 inch drive square (1 inch equals 25.4 mm) and the ratchet mechanism in such a way as to tighten the toothed belt (this operation is performed with the spark plugs removed)