- a special template or a wide metalworking ruler;
- set of flat feeler gauges;
- valve grinding tool;
- lapping paste.
Examination
1. Remove the cylinder head (see "Cylinder head - removal and installation").
2. We clean the cylinder head and bearing housing from dirt and carbon deposits, wash it from oil deposits, and remove carbon deposits from the walls of the combustion chambers with a metal brush.
3. Carefully inspect the cylinder head and bearing housing. There should be no cracks on them. There should be no burrs or traces of metal drag on the working surfaces of the camshaft supports, bearing housings and walls of the hydraulic tappet mounting holes. The valve guides and seats must fit tightly in the head body, without any signs of displacement during the operation of the timing system. The valves and their seats must not have cracks or signs of burning.
4. Check the flatness of the cylinder head using a special template.
Note: If there is no template, then you can check the lower mating plane of the head with sufficient accuracy using a wide metalworking ruler. We apply the ruler with its edge diagonally to the plane of the head. We make sure that there is no gap between the edge of the ruler and the plane of the head. The gap can be observed both in the middle part of the plane and at its edges. We measure the gap along both diagonals using a set of flat feeler gauges.
The maximum allowable gap is 0.1 mm.
If the gap is greater than the permissible value, the head must have its mating surface milled or replaced.
Warning! The cylinder head should only be replaced together with the bearing housing.
5. Check the tightness of the cylinder head. To do this, we plug the window on the end surface of the head that supplies coolant to the thermostat (you can install the thermostat pipe by placing a gasket cut from sheet rubber underneath it). We turn the head over and fill its internal cavities for coolant with kerosene.
6. Make sure there is no kerosene leak from the cylinder head.
Recommendation. If a leak is detected, or if there are cavities on the mating surface, you can try to repair the cylinder head using cold welding or replace it.
7. To check the tightness of the cylinder head valves, place it on a horizontal surface with the mating surface facing up.
8. Fill the combustion chambers of the cylinder head with kerosene and wait a few minutes. If the kerosene level in any chamber drops, then one or both valves are leaking.
Recommendation. Valve leaks can be eliminated by grinding if there are no cracks, pits or mechanical damage on the valve plate and seat.
1. Remove the oil seal from the valve (see "Valve stem seals - replacement").
2. Remove the valve from the guide sleeve.
3. Apply lapping paste to the working edge of the valve.
4. Install the valve into the cylinder head and attach the valve grinding tool to its stem.
5. Pressing the valve against the seat, turn it from side to side. After 10-15 movements, turn the valve 90° and continue grinding.
6. We grind until a uniform ring-shaped rim is formed on the valve plate...
...and his saddle.
7. Remove any remaining lapping paste from the valve and its seat.
8. Install the valve in place in the reverse order of removal.
Recommendation. During assembly, we install new oil scraper caps.
9. We grind the remaining valves in the same way.