Where is the oil check valve located on an Audi A6?

[IrisFitz]

The check valve on an Audi A6 is located in the oil passage from the oil filter to the cylinder head, mostly on the oil filter base. The pressure relief valve is on the oil pump, and the overflow valve is inside the oil filter. Classification of oil check valves: An oil check valve is a device in the automotive hydraulic system that prevents reverse flow of oil, divided into straight-through check valves and right-angle check valves. Introduction to check valves: A check valve allows fluid to flow only from the inlet to the outlet, preventing backflow of the medium, commonly known as a one-way valve. Check valves are also called non-return valves or backflow preventers. They are used in hydraulic systems to prevent reverse oil flow or in pneumatic systems to prevent reverse flow of compressed air. There are two types of check valves: straight-through and right-angle. Straight-through check valves are installed on pipelines with threaded connections. Right-angle check valves come in three forms: threaded connection, plate connection, and flange connection.