Make sure the blind holes in the cylinder block are clean, paying particular attention to the absence of traces of oil on their bottom, since oil compression when tightening the mounting bolts can cause cracks in the cylinder block.
Install the cylinder head gasket (it can only be installed in one position). Lubricate the front of the gasket (from the drive side of the gas distribution mechanism) sealant such as Curil or Atmosit.
Note. On the model «520i» a cylinder head gasket with a reinforced metal lining was used. It can be used for BMW carbureted engines «518» And «520», but the reverse substitution is not possible.
When installing the camshaft, its flange must be in the following position:
- models «518» And «520»: The dowel pin hole must face down and the groove on the top must line up with the boss on the cylinder head (see photo);
- models «525» And «528»: The locating pin on the flange must be at an angle of about 45°downwards and to the left. The upper threaded hole of the flange must be against the tide on the cylinder head (see photo).
In both cases, the piston of the 1st cylinder (counting from the drive of the gas distribution mechanism) must be at TDC. The mark on the bottom cover of the timing gear should be against the second mark on the crankshaft pulley.
Install the cylinder head and gradually tighten the bolts of its fastening in three steps in the order indicated by the moments of 3.5-4.5 kgf·m and 6.0-6.5 kgf·m.
Install the camshaft sprocket with the chain put 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 top cover of the timing mechanism, the plunger and the spring of the chain tensioner; at the same time, the plunger head should enter all the way into the tensioner body.
Adjust valve clearances.
Set ignition timing (cm. Here or Here).
Further installation of a head of cylinders is carried out in an order, the return to removal.
Fill the cooling system with fluid, start the engine and check for leaks.
From model year 1978 installation of the cylinder head of BMW engines «525», «528» And «528i» performed with the following in mind:
- on «528i» fasten the hose clamp that goes to the dispenser-distributor in such a way that the fastening screw is on the side of the throttle switch;
- when installing hoses 15 and 16 of the interior heater, do not rearrange them - hose 15 is connected to the drain line at the top, and hose 16, coming from the cylinder head, at the bottom.
By BMW «520» And «520i» with a 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 bolts and lightly lubricate their threads with engine oil;
- make sure that there is no oil in the blind holes of the cylinder block;
- tighten the head mounting bolts with rolled torques in the order shown in the photo in three steps,
- check the condition of the sealing rings of the compensating tube and, if necessary, replace them;
- make sure that the piston of the 1st cylinder, the camshaft and the ignition distributor are in the TDC position;
- put on the timing belt of the camshaft drive and adjust its tension;
- make sure the camshaft is in the correct position;
- install the toothed belt guard while attaching the engine lifting lug;
- install the TDC sensor, providing a gap of 0.2-2.0 mm between its end and the 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 clearance in the valve drive and install the cylinder head cover with a new gasket;
- adjust the idle speed of the engine;
- after 1000 km of run tighten bolts of fastening of a head of cylinders. Never loosen the cylinder head bolts.
Replacing the cylinder head gasket on «520» And «520i» with 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 the new head gasket, paying attention to its correct position over the coolant passage holes
Turn the camshaft 1-2 turns against the direction of rotation of the crankshaft using a 1/2 drive square" (1 inch equals 25.4 mm) and ratchet so as to tension the toothed belt (this operation is performed with the spark plugs turned out)