Cometic’s Multi-Layer Steel (MLS) head gaskets are widely regarded as a premium solution for sealing high-performance and stock engines in BMW inline 4 and 6-cylinder models. Proper installation is essential to ensure longevity, prevent leaks, and maintain engine integrity. This guide draws directly from manufacturer documentation, product manuals, and technical installation instructions provided by Cometic and its official partners.
The following instructions apply to Cometic MLS head gaskets used in BMW M40, M42, M43, M44, M50, M52, S50, and S52 engines. These gaskets are specifically engineered for the unique tolerances and requirements of BMW’s inline engines and are not suitable for use in engines with O-rings or receiver grooves around the cylinder bores.
Cometic MLS head gaskets are constructed from multiple layers of stainless steel, some of which are coated with proprietary high-temperature materials. The number of layers varies depending on the application and is designed to compensate for cylinder head lift, provide even clamping force, and create a chemical bond on the first heat cycle. This bonding process is critical for forming a durable and reliable seal between the engine block and cylinder head.
The installation process requires meticulous attention to detail, particularly in ensuring that the mating surfaces are flat, clean, and free from oil, debris, and coolant residue. Cometic explicitly advises against the use of sealants, as the gaskets are pre-coated with Viton rubber and are designed for dry installation. The following steps outline the best practices for installing Cometic MLS head gaskets in BMW engines.
Pre-Installation Preparation
Before beginning the installation process, it is crucial to prepare the engine block and cylinder head surfaces to meet the required specifications. According to Cometic and the accompanying installation instructions, the mating surfaces must:
- Be smooth with a surface finish of 50 Ra or finer.
- Be completely flat, with no warping or deformation.
- Be free from oil, coolant, or old gasket material.
- Be visually inspected for nicks, scratches, or imperfections that could compromise the seal.
The engine block and cylinder head should be cleaned using a degreaser or solvent to remove all traces of oil and residue. A flatness check is also recommended using a straight edge and feeler gauge. If the surfaces are not within acceptable tolerances, resurfacing may be necessary before proceeding with the installation.
The Cometic PRO2037T-845-030 Thick Ex/Head/Intake/WP Gasket Kit, for example, is designed for high-performance applications and includes a variety of gasket components. The installation manual for this kit emphasizes the importance of ensuring that all mating surfaces are clean and undamaged before proceeding. It also recommends that installation be performed by a qualified professional, given the precision required.
Step-by-Step Installation Instructions
Position the Gasket on the Clean Surface
Carefully place the Cometic MLS head gasket onto the clean and dry engine block surface. Ensure that the gasket is properly aligned with the bolt holes and intake/exhaust ports. Avoid twisting or bending the gasket during this step.Align the Cylinder Head
Once the gasket is in place, position the cylinder head on top of the gasket. Ensure that the head is aligned with the gasket and the engine block. Avoid forcing the head into place, as this can damage the gasket or misalign components.Install Head Bolts or Studs
Insert the head bolts or studs into their respective positions. If using new bolts or studs, ensure they are of the correct type and specification for the engine. Cometic recommends the use of aftermarket fasteners for improved performance and reliability.Tighten Fasteners According to Manufacturer Specifications
Follow the recommended torque sequence and values as specified in the vehicle’s service manual. The use of a calibrated torque wrench is essential to ensure even clamping force across the gasket. Failure to follow these specifications can lead to gasket failure or engine damage.Re-Torque After Initial Startup
After the initial tightening, it is recommended to re-torque the head bolts or studs once the engine has been started and allowed to cool to room temperature. This step ensures that the gasket is properly seated and compressed.Avoid Use of Sealants
Cometic MLS head gaskets are pre-coated with Viton rubber and are not intended to be used with additional sealants. The use of sealants can interfere with the gasket’s ability to conform to the mating surfaces and may reduce its effectiveness.
Technical Considerations and Customization
Cometic MLS head gaskets are available in a wide range of thicknesses, typically from 0.027 inches to 0.140 inches. The thickness of the gasket can be adjusted based on the specific engine build and desired compression ratio. For example, the M40 and M42 engines use a 0.070-inch-thick gasket with an 84mm bore, while the M43 and M44 engines use a similar 0.070-inch-thick gasket with an 85mm bore. The M50 and M52 engines use a 0.070-inch gasket with an 84mm bore, while the S50 engine uses an 86mm bore and the S52 engine uses an 86.4mm bore.
Cometic also offers MLX head gaskets, which include an additional “stopper” layer designed for more sensitive applications. These gaskets feature a fold-over layer that forms a torque-limiting surface to help reduce the risk of combustion seal issues. An additional high-temperature polymer is paired with specialized embossments to form a micro seal against fluids.
For complete engine builds, Cometic provides StreetPro Gasket Kits, which include all necessary gaskets and seals for a given application. These kits are designed to simplify the ordering process and ensure that all required components are included in a single package.
Compatibility and Application Specifics
Cometic MLS head gaskets are compatible with a wide range of BMW inline 4 and 6-cylinder engines, including:
- M40B16, M40B18, M42B18, and M44B19 inline 4-cylinder engines used in the E30 and E36 3 Series and E34 5 Series.
- M50, M52, S50, and S52 inline 6-cylinder engines found in the E34 5 Series and E36/E36/7 Z3 models.
Each gasket is designed to match the factory specifications of the respective engine, including bore size and thickness. For example, the M40 and M42 engines use a 0.070-inch gasket with an 84mm bore, while the M43 and M44 engines use a 0.070-inch gasket with an 85mm bore.
It is important to note that Cometic MLS head gaskets are not suitable for use in engines with O-rings or receiver grooves around the cylinder bores. These gaskets require smooth and flat surfaces to function properly, and using them in engines with such features can lead to sealing issues.
Post-Installation Checks and Maintenance
After installation, it is essential to monitor the engine for any signs of leaks or performance issues. This includes checking for oil, coolant, or exhaust gas leaks around the gasket area. During the first few operating cycles, it is recommended to closely monitor engine temperature and fluid levels.
Some applications may require a re-torque of the fasteners after a specific break-in period or after several temperature cycles. It is advised to consult the vehicle’s service manual for specific recommendations regarding post-installation maintenance and re-torquing procedures.
Cometic gaskets are designed for durability and long-term sealing. Regular maintenance of the engine and associated systems will contribute to the longevity of the gasket. General maintenance tips include:
- Regularly checking and changing engine oil.
- Ensuring proper coolant levels and quality.
- Monitoring for any signs of overheating or misfiring.
Conclusion
Cometic MLS head gaskets offer a reliable and durable sealing solution for BMW inline 4 and 6-cylinder engines. The installation process requires careful preparation, precise alignment, and adherence to manufacturer torque specifications. By following the outlined steps and technical recommendations, users can ensure a successful installation that enhances engine performance and reliability.
The use of Cometic’s MLS head gaskets in high-performance and stock applications demonstrates the brand’s commitment to quality and innovation. Whether used in a daily driver or a modified engine, these gaskets provide a consistent and dependable seal when installed correctly.