THE BIG FOUR >Contents
THE BIG FOUR >Contents
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THE BIG FOUR
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.

The 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.

 

The Big
Four

  • Oil
  • Valves
  • Timing
  • Cooling
1. Oil - Frequent checks & Oil Changes every 3000miles
More on Oil


2. Valves - Valve Adjustment every 3000miles
More on Valves

 

 

3. Timing - Regular Checks to avoid problems such as pre-ignition
More on Timing
4. Cooling - Cooling System & Cooling Tinware require checks
More on Cooling

Avoiding Unnecessary 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.
Therefore, 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.

  • Inefficient 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.
  • Insufficient Oil - VW engine contains a relatively small volume of oil (2.5 litres / 4 pints), this leaves little room for error. Even a small decrease in the volume of oil will have a marked effect on engine temperatures.
  • Oil 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.
  • Tight 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.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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