Cylinder head gasket
The cylinder head gasket (ZKD) is an important component in almost every combustion engine between the crankcase and cylinder head . It fulfills the task of sealing the combustion chamber as well as the cooling water and engine oil ducts. It also serves to transmit power between the two components and therefore has a decisive influence on the distribution of power within the system.
The first internal combustion engines in the history of Étienne Lenoir , Nikolaus Otto and Gottlieb Daimler were built with sack cylinders and therefore did not require a cylinder head gasket. Sack cylinders were in use until the 1930s. The V4 engine of the 1898 Mor was one of the first known engines with a removable cylinder head . The first mass-produced automobile with a removable cylinder head was the Ford Model T , which came onto the market in 1908. With the separation of the components cylinder and cylinder head, the requirement of the sealing and thus the concept of the cylinder head gasket, also called head gasket for short, arose.
Importance of the cylinder head gasket
A defective cylinder head gasket is one of the most common types of engine damage and can have the following effects:
- The combustion gases enter the cooling water room. Consequences: Steam escapes at the pressure relief valve of the expansion tank. The cooling capacity is reduced due to the high gas content in the cooling water. Accumulations of combustion gases in the cooler further reduce the cooling performance. There is a risk of overheating.
- The engine oil passes into the cooling water. Consequence: brownish deposits in the water circuit, small cooling water channels (e.g. in the radiator) can clog.
- Cooling water penetrates the lubricating oil circuit. Consequence: deteriorated lubricity of the engine oil, risk of bearing damage or similar.
- The cooling water enters the combustion chamber. Possible consequence: white steam, increased corrosion in the combustion chamber and exhaust system. With larger accumulations of cooling water in the combustion chamber there is a risk of water hammer .
- The combustion gases get into the ambient air. Consequence: smoke development, risk of engine fire, risk of toxic exhaust gases in the interior ventilation.
Types of cylinder head gaskets
In the early days of engine construction up to the 1960s, cylinder head gaskets were cut out of thin sheets of cork . Even today, engines with air cooling only need comparatively simple cylinder head gaskets, since they only have to be sealed against combustion gases and not the cooling water.
Today the cylinder head gasket is mostly a very complex component that is subject to high thermal and mechanical loads. Their production is complex because of the expensive tools required. It consists of a carrier plate or a metal grid that is embedded in a heat-resistant plastic compound. The surface is often provided with an anti-stick layer. The recesses in the combustion chamber and the other holes are crimped .
Ferrolastic soft material ZKD
The ZKD made from asbestos-free Ferrolastic soft materials came into use at the end of the 1980s when the company switched to asbestos-free materials. The flat seal made of serrated sheet metal with soft material applied on both sides requires high screw forces and has only low elasticity, which means that sealing gap vibrations and changes in thermal pressure cannot be compensated for. The high combustion pressures and the need for a lighter design in modern engines and thus smaller sealing surfaces has pushed this type of seal to its limits and triggered the development of more powerful systems.
The metal- elastomer seal is characterized by the separation of the sealing systems from the combustion chamber and fluid channels. While the combustion chamber is sealed by means of plastic beads or elastic systems, this is done in the case of the liquid channels with elastomer sealing lips that adapt optimally and are highly elastic. However, the elastomer material must be adapted to the media flowing in the channels. The screw forces required for the sealing effect are significantly lower.
Metal layer ZKD
They represent the latest development and have been used in large-scale production since 1992 as metal layer steel seals (MLS = Multi Layer Steel). The seals, which are made of spring steel, are matched to the required sealing effect by differently forming the beads. Since the metal surfaces of the engine block, gasket and cylinder head do not achieve the necessary tightness against each other, these surfaces are sealed against each other by very thin layers of elastomer. These layers are partly flat, partly carried out and must be resistant to the media and temperatures that occur.
Engines without a cylinder head gasket
There are also engines that can do without a cylinder head gasket. The engine of the VW Beetle has precisely machined fits on the individual cylinders, which ensure the necessary sealing.
Even air-cooled diesel engines rarely have a proper cylinder head gasket. Instead, the cylinder and the cylinder head are ground in. In order to obtain the correct gap , foot gaskets (between the cylinder and engine block) or steel washers between the cylinder and the cylinder head are used. An example of this construction method are the FL engines from Deutz , which until the 1980s, the truck of Magirus-Deutz drives and still widely used for. B. are in construction machinery . Large diesel engines which are installed in ships, for example, have a soft iron ring instead of a classic cylinder head gasket for the purpose of sealing between the cylinder liner and cylinder head. This is a wearing part and can only be used once.
Crosley engines have blind cylinders and therefore no cylinder head gasket either.
- Kurt-Jürgen Berger, Michael Braunheim, Eckhard Brennecke: Technology automotive engineering. 1st edition, Verlag Gehlen, Bad Homburg vor der Höhe, 2000, ISBN 3-441-92250-6 .
- Peter Gerigk, Detlev Bruhn, Dietmar Danner: Automotive engineering. 3rd edition, Westermann Schulbuchverlag GmbH, Braunschweig, 2000, ISBN 3-14-221500-X .
- Hans Jörg Leyhausen: The master craftsman's examination in the automotive trade part 1. 12 edition, Vogel Buchverlag, Würzburg, 1991, ISBN 3-8023-0857-3 .
- Peter A. Wellers, Hermann Strobel, Erich Auch-Schwelk: Vehicle technology expertise. 5th edition, Holland + Josenhans Verlag, Stuttgart, 1997, ISBN 3-7782-3520-6 .
- ^ Anthony Bird: Antique Automobiles (1984), 37.