NOTE: The camshaft adjustment units can only be
changed as a complete set during servicing. They cannot
be repaired.
This system uses electro-hydraulically regulated
camshaft adjustment. The timing of the intake and
exhaust valves can be controlled independently of one
another using a pressurized engine oil supply which is
controlled by solenoids.
NOTE: When repairing parts of the timing gear which
operate under engine oil pressure, extreme cleanliness
is vital. Particles larger than 0.2 mm in diameter can
cause the valve adjustment to fail.
Upon starting the engine and during idling, both
camshafts are mechanically locked in their starting
positions. The exhaust camshaft is in the advanced
position and the intake camshaft is in the retarded
position.
The camshaft adjuster on the exhaust side has a torsion
spring which compensates the camshaft drive torque.
This ensures, under all operating conditions and when
the engine is turned off, that the assembly can return to
the starting position.
Internal exhaust gas recirculation can be realized through
continuous adjustment of the timings. The resulting
de-throttling of the engine results in better fuel
consumption and more favourable combustion
temperatures at which fewer pollutants are generated.
VCT can also optimise the camshaft timing to maximize
engine performance at wide open throttle.
The camshaft timing must be performed whenever either
the front camshaft bolts or the crankshaft pulley bolts
have been loosened. This must be done as the camshafts
and the crankshaft don’t have keyways for chain wheel
or pulley location. The friction washers must be replaced
whenever a camshaft chain wheel or crankshaft pulley
bolt has been loosened.
NOTE: If the crankshaft pulley or VCT unit bolts are
loosened, the camshaft timing procedure needs to be
performed.
When replacing the timing chain there are a number of
special tools which are required to ensure correct engine
timing:
If the crankshaft pulley or VCT unit bolts are loosened,
the camshaft timing procedure needs to be performed.
When replacing the timing chain there are a number of
special tools which are required to ensure correct
camshaft timing:
•
303-507 Crankshaft locking tool
•
303-1565 Camshaft alignment tool
•
303-1521 CKP alignment tool
E182334
303-507
E202225
303-1565
E137263
303-1521
1
2
x2
3
33
Service Training
Engine
Lesson 3 – Powertrain
