Abstract: A cover assembly is provided to be secured to the upper end of an exhaust pipe of an internal combustion engine maintained outdoors in such a manner such that a cap forming part of the assembly will cover the end of the exhaust pipe when the engine is quiescent. When exhaust gases exert pressure in the pipe during operation of the engine the cap will be raised against gravity off the end of the pipe to permit the gases to escape. The movement of the cap between open and closed positions is a rocking movement about a pivot and normally results in considerable clatter as the parts strike metal. Means are provided by the invention to reduce the clatter.