Timng belts are made from reinforced rubber that rotate around the camshaft sprockets, idlers, tensioners and the crankshaft sprocket. In many engines the belt also drives the water pump. You should always replace the belt and tensioner if you notice any wear, damage or noise coming from an idler or tensioner. You must also replace these items when recommend by the vehicle manufacturers service schedule. All engine has a different replacement interval and you should follow these guidelines. Failure to replace the belt kit will result in a catastrophic engine failure which may lead to bent valves, cracked guides, broken cam train, damaged pistons and much more. It is is crucial that you have this checked regularly. 

We keep Timing belt kits in AE, Dayco, FAI, INA & Gates

Trouble Tracer Chart 

Timing belt cross section


Noise prior to failure: Whining from over tightness. Failing belt whipping the enclosure. Slapping noises from a slack belt.

Failure: A few popular engines are designed such that the valves when fully open will not contact the piston at top dead centre. Cam belt breakage will stop the engine but should not cause any damage. However, on most engines, timing belt failure results in major damage. These are called "interference engines". Valve to piston contact often occurs requiring replacement of valves, valve guides, camshaft pistons, and possibly cylinder head and block repair.


Do not refit a timing belt. Engine manufacturers specify the tension to which a new belt should be set. In operation however, the tension will relax slightly to a lower value. If a used belt was refitted, and tensioned to the manufacturer‘s figure for a new belt, it would run too tight in use. As it is almost impossible to refit a belt to the tension it ran at before removal, it is recommended that belts should never be refitted. Change your belt at the interval specifi ed by the vehicle manufacturer. Due to the constant flexing the fibres of the tension cords eventually fatigue, and break. The life of a belt depends upon many factors including: the tensile forces it transmits, its width, its overall length, the design of the cords, the size of the pulleys and the torsional vibration characteristics in the engine. The manufacturers replacement period has been established so that a belt is renewed before the fatigue may cause it to fail, and should be adhered to.

Storage of timing belts. Timing belts are rubber composite products and as such should be stored away from sunlight, oil, water and solvents. They should not be crushed or bent tightly, for example by hanging on a peg.


All failures require the engine to be rebuilt to the manufacturers specification replacing all damaged components. In particular, ensure that:

• The belt is correctly tensioned.
• The tensioner mechanism operates correctly and is properly secured.
• All idler wheels and auxiliary shafts rotate freely.
• The gears are clean, undamaged, and in alignment.
• The enclosure is in good order.
• Any oil leakage into the enclosure has been stopped.
Foreign Body Entrapment
edge wear on timing belt

Symptom: Belt breakage, in a
curved or ragged tear.
Cause: A foreign body has become
trapped in the drive and
has over-stretched and broken
the tensile cords.
Remedy: Attempt to locate and
identify foreign body (nut, bolt,
washer etc). Ensure belt enclosure
is effective. Set new belt
tension and ensure tensioner
mechanism is tight.

Edge Wear
edge wear on timing belt

Symptom: Excessive wear and
damage to the belts edge.
Cause: Damaged gear flange,
or misaaligned gears.
Remedy: Replace damaged
gears and ensure correct belt
Set new belt to correct tension
an ensure tensioner mechanism
is right.


Land Wear
edge wear on timing belt

Symptom: Wear, or polishing,
on the lands between the teeth,
possibly wearing down to the
tension cords‘ with polishing on
the tooth crests of trapezoidal
Cause: Excessive tension,
causing the belt to wear on the
gear lands. Rough gears abrading
the belt.
Remedy: Replace gear(s) if required.
Set new belt to correct
tension and ensure tensioner
mechanism is tight.

Tooth Peel
edge wear on timing belt

Symptom: Teeth peeling, emanating
from root cracks. Often
is present together with tooth
Cause: Very low tension allowing
the belt to jump teeth.
Remedy: Set new belt to correct
tension and ensure tensioner
mechanism is tight.

Tooth Sheer
edge wear on timing belt
Symptom: Six or more teeth
missing, often with cracking in
roots of a number of teeth.
Cause: May be due to sudden
overload of the drive from the
seizure of a driven part, such as
a water pump.
Also may be due to low tension,
which allows the belt to ride
high on the gear, producing
excessive bending moments,
and defl ection of the teeth until
cracks form.
Remedy: Ensure all driven
items rotate smoothly.Set new belt to correct tension
and ensure tensioner mechanism
is tight.
Tooth Wear
edge wear on timing belt
Symptom: Hollows through
the facing fabric.
Cause: Extremely low tension
allows the belt to ride out on
the gear, causing localised
wear on edge of the thrust face.
Sometimes excessive tension,
pulling the belt up the land,
may wear the tooth face, before
a tensile failure.
Remedy: Set new belt to correct
tension and ensure tensioner
mechanism is tight.

Oil Contamination
edge wear on timing belt
Symptom: Dirty or smelly belt,
with a ragged decomposing
Cause: Contamination from a
failed oil seal, or an oil or diesel
leak, breaks down the adhesion
of the rubber. Swelling
can also occur and cause mismeshing
leading to other types
of failure.
Remedy: Ensure oil leak is
stopped. Check belt enclosure
and dust shields. Set new belt
to correct tension and ensure
tensioner mechanism is tight.

Tensile Failure
edge wear on timing belt
Symptom: Tensile breakage,
with a straight break between
two teeth.
Cause: Some of the tensile
cord‘s fi bres have broken due
to crimping (folding) before
or during assembly, creating
a weak point. A belt running
over-tensioned may sometimes
cause teeth to ride up onto gear
lands, resulting in vast over
stretching and tensile failure.
Remedy: Replace belt carefully,
without pinching or levering.
Set new belt to correct tension and ensure tensioner mechanism
is tight.
Back Cracks
edge wear on timing belt
Symptom: A series of cracks
across the back of the rubber
Cause: The rubber has been
over-heated and has degraded,
possibly from friction on a
seized idler or water pump. Extreme
cold may have the same
Remedy: Ensure all spindles
driven off the back of the belt,
including water pumps, rotate
freely. Set new belt to correct
tension and ensure tensioner
mechanism is tight.


Timing Belt kit supplier


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