SKF Timing Belt Kits - SKF.com

Failure analysis overview
Timing belt
The material in the belt is sensitive to bending
(crimping) more than its maximum natural curve, and
should therefore be treated gently.
Common failure causes:
1. Incorrect tension.
2. Misalignment.
3. Foreign object in the drive system (oil, cooling liquid,
water, stone, etc).
4. Contamination or uneven surface between the
tensioner mounting plate and the engine block.
5. Tensioner/Idler failure.
6. Worn crankshaft or camshaft dampers.
2. Misalignment (incorrect centering of the belt)
The edge of the belt has been worn down to almost half its size. On
the tensioner, you can see clear marks indicating a misaligned belt.
4. Contamination on the belt
If the belt has been contaminated with oil or water, you will see this by
the glazing on the belt. You may feel it, as the belt will be soft and the
rubber coming away from the construction.
12
1. Incorrect tension
You can see on the tensioner that the surface has been colored blue/
brown from the heat. On the belt you see traces of wear in the middle.
This indicates that the tension is too high, i.e. bad mounting.
3. Foreign object in the timing drive system
You can see on the belt pictures, showing both sides, that a foreign
object, or perhaps a damaged tooth on the pulley, have made marks in
the belt that eventually cracked.
Engine type
Depending on the design of the engine, the piston
and valve paths may “interfere” with one another, and
incorrect timing in their movements may result in
the piston and valves colliding. (Such designs are also
called “interference head” or “interference engines”.
Conversely, non-interfering engines are called “freewheeling”
or “non-interference” engines.)