Properties of Sealing Surfaces
Also in future, MLS head gaskets will represent the leading sealing concept. Already today, sealing between cylinder head and engine block is achieved almost exclusively by means of multi-layer steel head gaskets. However, it is not only the head gasket‘s quality that is responsible for perfect sealing. An equally important role is played by the surface qualities of cylinder head and engine block.
The demands placed on the surface finish are a decisive factor for reliable sealing results. Therefore, it is essential that the specified values are observed when installing head gaskets. Hereby, there is no difference between composite gaskets and MLS gaskets.
The following surface deviations lead to reduced surface qualities of cylinder head and engine block:
- Component unevenness
- Component distortion
- Waviness (deviations in parallelism)
- Roughnesses (grooves and scores)
Example of influences of surface quality due to surface deviations on an engine block.
The standards for the surface texture are defined in DIN EN ISO 4287. The corresponding values are Rz ≤ 15 μm for roughness, and Pt ≤ 22 μm for profile depth. Consequently, cylinder head gaskets must provide comprehensive macro and micro sealing properties.