Cylinder head repair (BMW 5 Series E12)

Replacing valve guide bushings

If one of the valve guide bushings is heavily worn (see wear limits in subsection "Detailed technical specifications") replace it.

On a cold engine, press out the guide bushing using tool 609, moving the bushing from the top of the cylinder head to the combustion chamber.

Check the dimensions of the guide bushing seat in the cylinder head. If the seat diameter is larger than the specified (see "Detailed technical specifications"), bore the socket to one of the larger sizes and install a bushing of the corresponding repair size.

Heat the cylinder head uniformly to a temperature of about 200°C (no more), lubricate the valve sleeve with consistent grease and press it in with mandrel 610 in the direction from the top of the cylinder head to the combustion chamber until the mandrel stops against the cylinder head. Using mandrel 610 ensures proper protrusion "A" of the valve sleeve relative to the plane of the cylinder head, which should be within 15±0.5 mm (see photo).




After the cylinder head has completely cooled, ream the hole in the guide bushing to ensure the correct size is obtained.



Make sure the new guide bushing and valve seat are perfectly aligned. Resurface the valve seat if necessary.

Since model year 1978 on BMW "525", "528" and "528i" replacement of valve guide bushings is carried out taking into account the following:

• press out the guide bushing with mandrel 111100;
• the length of the guide bushings has been changed. The length of the old bushings is 52 mm. The new bushings can be installed in place of the old ones.
• press the guide bushing into the heated cylinder head in the direction from the camshaft to the combustion chamber;
• the hole in the mandrel 111120 provides the required pressing depth (protrusion "A" of the sleeve);
• for a valve sleeve of a modified length, the protrusion "A" is 13.5±0.5 mm. Insert a 1.5 mm thick washer into the hole of the mandrel.

Replacing valve seats

Replacement of valve seats must be carried out at a service station.

Drill out the valve seat to be replaced, paying attention to precise centering of the drill and avoiding removing metal from the valve seat seat.

Ream the valve seat, maintaining the specified value of the valve seat interference in the cylinder head seat (see subsection "Detailed technical specifications").

Heat the cylinder head uniformly to 200°C and cool the valve seat to minus 70°C by immersing it in liquid nitrogen.

Press the valve seat until it rests against the bottom of the cylinder head socket.

Grind the working chamfer of the valve seat.

Grinding of valve seats and valves

Check the condition of the valve working chamfer. In case of minor damage, it can be ground down, maintaining the proper chamfer angle.



Grind the working chamfers of the valve seats by hand or with a grinding machine.

Grind the valves to the seats and check the tightness of the valves to the seats.

After grinding and lapping the seats and valves, thoroughly wash the seats, valves and cylinder head channels, blow them out with compressed air.

Check the tightness of the valves' fit to the seats by filling the combustion chambers with kerosene, after screwing in the spark plugs.