Timing Chain Tensioner and Drive Gears

Fig 1: Hydraulic Tensioner Mechanism

Courtesy of BMW OF NORTH AMERICA, INC.

Fig 2: Timing Chain In Service Position

Courtesy of BMW OF NORTH AMERICA, INC.

Workshop Hint 

Before reinstalling the timing chain tensioner the plunger must be placed in the "transit" position. This is achieved by pushing the plunger fully in until it locks in place.

This moves the mechanical ratchet mechanism to the start position. When the tensioner has been installed in the engine, the chain guide is pushed towards the tensioner to release the plunger ratchet mechanism to apply the correct amount of tension to the timing chain.

Fig 3: Crankshaft Gear

Courtesy of BMW OF NORTH AMERICA, INC.

Fig 4: Camshaft Gear

Courtesy of BMW OF NORTH AMERICA, INC.

A key way locates the crankshaft gear (23 Teeth). The camshaft timing gear (46 Teeth) is located by a key way and is retained by a central bolt. The camshaft gear is driven by a roller timing chain.