Valve seats (BMW X5 E53)

Valve seats are made of austenitic steel obtained by powder metallurgy and are not replaceable. If traces of burning or wear are detected that cannot be removed by grinding, the cylinder head is replaced entirely. In this case, it is necessary to maintain the maximum permissible size. If this size is exceeded, then the reliability of gap compensation during operation of hydraulic tappets is impaired. The valve seat is ground until a reliable valve spot is obtained. Valve seats have an additional narrowing - the angle of external correction and during processing it is necessary to maintain it - 15° (Fig. 3.5).



The technology for grinding valve seats is identical for all engines. The valves are ground to the seat using only fine-grained grinding paste. The valve seats are ground using a rotary motion with frequent separation of the valve from the seat and its rotation. To hold the valve, use the device "00.3.520" or "00.3.580" (Fig. 3.6). Traces of grinding paste must be carefully removed after grinding.





The quality of lapping should be checked by the contact patch and by filling the valve plate with kerosene. Fuel leakage through the valve guide is not allowed; repeated lapping is required.