Although small in number in comparison to the number of engines actually built, engines do fail. In this article, Ivor Searle, the UK's leading engine remanufacturer, takes a look at the primary causes of engine failure.
The engine is the heart of a vehicle and, just as with human beings, it needs to be properly cared for in order for it to function properly. A neglected engine will ultimately fail, resulting in the need for repair, replacement or, in the worst-case scenario, the vehicle being scrapped should the cost of repair or replacement become economically unviable.
If we examine the causes of failure in both petrol and diesel engines, it’s clear that there are several causes and most likely combination of causes, that lead to failure. These include a lack of maintenance, component wear, contamination of the fuel, lubrication and exhaust system issues, head gasket failure, insufficient lubrication, misfuelling and overheating. The symptoms of these problems are equally varied and include poor running, excessive emissions, high oil consumption, knocking sounds from the engine and low oil pressure, as well as low compression and oil mixing with coolant. Other common causes of engine failure include ‘hydraulic’ contamination when a vehicle is driven into water which is then ingested into the engine, or when a timing belt or chain breaks.
Contamination is a root cause of engine failure and is not just confined to within the engine itself, but also to components beyond the combustion chamber, such as problems with the vanes sticking on the variable geometry turbochargers fitted to diesel engines. Today’s engines are equipped with various technologies to ensure they produce low emissions and the best possible fuel economy. This, paired with the increasing use of biodiesel and ethanol based fuels, has led to increased levels of contamination in the fuel, lubrication and exhaust systems. Filters, such as DPFs (Diesel Particulate Filters) in the exhaust system, add a restriction and therefore increase back pressure and the potential for contamination to flow upstream into the engine and create problems in the fuel and lubrication systems, as well as the exhaust. The latest cars still produce the same amount of soot and carbon deposits as their predecessors emitted two decades ago. The difference now is that these deposits are not released into the atmosphere which can lead to inlet manifold, fuel system, EGR valve and oil system contamination.
Head gasket failure
Head gaskets are designed to prevent unwanted oil and coolant from entering the combustion chamber. When a head gasket fails, oil mixes with the coolant, causing the pistons to compete against fluids that are not designed to combust. Left untreated, this will result in the cylinder head warping and damage to the pistons and piston rings.
Oil is essential for the smooth running of an engine, lubricating moving parts to reduce friction, as well as playing a key role in engine efficiency through its heat transfer properties. Oil degrades over time, with contamination in the form of sludge, varnish and lacquer building up in the crankcase. Over time, this contamination results in the lubrication pathways within the engine getting blocked, restricting oil flow to critical moving components. This creates a ‘perfect storm’ which can lead to engine failure.
Despite the best efforts of the car manufacturers and oil companies, vehicle misfuelling continues to be a major cause of engine failure. This is particularly dangerous for diesel engines that have been filled with petrol, as the gasoline effectively acts as a high-power solvent throughout the diesel injection system, stripping out the lubrication which is crucial for the operation of the high pressure direct injection systems which are now commonplace. These ‘wet’ common rail systems produce injection pressures of up to 1,800 bar with the latest technology allowing for up to seven injection events per combustion stroke. With systems of this complexity, removing the lubrication results in the common rail pump heating up and metal on metal contact, leading to metal particles being drawn throughout the entire injection system.
Engines are generally designed to operate in a temperature range of between 60-90 0C. This deliberately wide range considers the environments and climates for most mass market vehicles, as well the thermal stresses in the light weight alloys used in engine construction. Cooling system problems, such as blocked hoses, low coolant or radiator damage, can result in overheating beyond the maximum range and the cylinder head and engine block warping.
About Ivor Searle
Ivor Searle is a leading independent producer of remanufactured engines and all major powertrain components. The company has made a major investment in the market and employs the same quality-focused ethos from over 70 years of engine remanufacturing expertise in its turbocharger facility, which is certified to ISO 9001:2008. Providing first class customer service is central to Ivor Searle’s ethos and ensures that customers can buy Ivor Searle turbochargers in complete confidence with the added reassurance of a comprehensive warranty. An extensive all makes programme covers petrol and diesel cars and light commercial vehicles, with new applications being constantly added to the extensive range.