Valve cover
The valve cover , and cylinder head cover called, is the chief conclusion of an (upright) four-stroke - combustion engine .
It houses the upper actuating elements of the valve train and prevents the lubricating oil from escaping into the environment and air from entering the engine: modern engines have a slight negative pressure inside to prevent combustion gases and vapors from entering the environment reach. The valve cover often also contains the filler opening for the engine oil including the toggle cap, see pictures of a TDI engine.
If the valve train is equipped with an overhead camshaft and this is driven by a timing chain (all engines from Daimler-Benz, many engines from BMW, some engines from Audi, etc.), the valve cover also includes the camshaft sprockets.
The valve cover is often sealed against the cylinder head with a U-shaped plastic gasket, the so-called valve cover gasket. For decades, the valve cover was sealed with a circumferential cork or pressed material seal, as was the case with the two valve covers of a VW Beetle engine (see picture). In the meantime, however, rubber or plastic seals are used almost exclusively. Most older engines can be exchanged for a plastic seal without any problems.
With advanced mileage, valve cover gaskets often leak and have to be replaced, otherwise engine oil can get into the environment and onto hot engine parts. If engine oil drips onto parts of the warm exhaust system, there is even a risk of fire in extreme cases.
A valve cover is missing from many very old engines. Then the valve train of the engine runs open and clearly visible; you can watch the valve springs etc. "at work". Any lubricating oil that may escape here has access to the environment.
Engine compartment of a Passat TDI from 1996, plastic cover removed, oil filler neck is part of the valve cover
Detail view
Valve cover of a Honda CB 450 S Bj. 1987; a camshaft ( SOHC ) is also covered
Valve cover of a Honda CB 750 Four F2 Super Sport Bj. 1978 ( OHC ) with valve clearance adjustment openings
Valve cover of a VW Beetle from 1975 with wire spring clip
literature
- Richard van Basshuysen , Fred Schäfer: Handbook internal combustion engine. Basics, components, systems, perspectives. 3rd completely revised and expanded edition. Friedrich Vieweg & Sohn Verlag / GWV Fachverlage GmbH, Wiesbaden 2005, ISBN 3-528-23933-6 .