Those engines with
the shortest lifespan are those poor engines which are driven hard and
given little servicing. One of the most famous and well-known features
of the Volkswagen engine throughout its life has been the fact that it
is air-cooled. However, there are certain disadvantages of an air-cooled
system. There is greater engine noise, more engine power is required to
drive the cooling fan and there is a less precise control of engine temperatures.
Heat is the air-cooled engine's greatest enemy, efficient cooling is vitally
important and efforts must always be made to avoid unnecessary additional
sources of heat. In addition the engine oil also plays a significant part
in assisting engine cooling, therefore, the lubrication system should
not be neglected. Oil must be in good condition if it is to cool and lubricate
the engine efficiently. As the engine has no adequate form of oil filtration,
frequent oil changes are absolutely mandatory for long engine life.
only way to assist engine longevity and efficiency is through, frequent
oil changes, regular tune ups and servicing at the correct intervals.
The following procedures are considered as being the "Big Four"
with regards to an engine's life expectancy.
Oil - Frequent checks
& Oil Changes every 3000miles
Valves - Valve Adjustment
Timing - Regular Checks
to avoid problems such as pre-ignition
Cooling - Cooling System
& Cooling Tinware require checks
Additional Sources of Heat
The usual cause of an
engine failure, even remotely maintained, is due to some part of the engine
becoming overheated past
the temperature where oil retains its ability to lubricate.
Overheating can cause components to over expand, reducing internal tolerances
to such an extent that oil can no longer get between moving parts to lubricate
them, leading eventually to seizure. Overheating will place excessive
thermal forces on components or simply melt them. Overheating within the
cylinder head or components may result in a secondary source of ignition
in the combustion chamber, it may ignite the fuel-air mixture instead
of the spark plug, this can cause pre-ignition and detonation which in
turn lead to more overheating and damage.
any unnecessary additional sources of heat need to be eliminated or reduced.
It is important to appreciate that the operation of the cooling and lubrication
systems along with the setting of valve clearances and ignition timing,
are all inter-dependent. If one or the other is fractionally adrift, it
can cause excess heat and will effect the remainder, the overall efficiency,
performance and lifetime of the engine will suffer.
Cooling System - Cooling Tinware, Grommets and Seals damaged
or missing, preventing cooling air from being directed over the cylinder
heads. The cylinder heads may then overheat.
- VW engine contains a relatively small volume of oil (2.5 litres
/ 4 ½ pints), this leaves little room for error. Even a small decrease
in the volume of oil will have a marked effect on engine temperatures.
in poor condition - Oil holds in suspension the unwanted
by-products of fuel combustion, such as silica (silicon oxide) and
acids, whilst also cleaning the engine of these by-products. It must
do all of these things whilst under tremendous heat and pressure.
The oil will eventually become saturated with unwanted material and
succumb to fatigue, no longer performing its duties efficiently. Engine
wear and overheating of internal components increases.
Timing too advanced
- If the timing is too advanced, pre-ignition can result. The spark
plug fires too soon, the fuel-air mixture will eventually detonate("ping")
instead of burning , causing excessive heat and pressure to the piston
top and cylinder head, resulting in expensive damage.
Valves - If a valve's clearance is too small the valve
will be unable to close completely, this will prevent the valve being
able to dissipate its heat efficiently through the valve seat into
the cylinder head. The valve will be in danger of burning or overheating,
which may provide a secondary source of ignition resulting in pre-ignition
and detonation causing engine damage.