What Causes Car Engines To Fail?

The engine is like the heart of the vehicle and so any issue with the engine can mean expensive repairs or even complete engine replacement. Without a healthy working engine, you cannot expect your vehicle to function so it is important to not only take care of your engine but also be aware of how the engine may fail and what you need to do to prevent that. Let us take a look at all the possible causes of engine failure, the symptoms that may arise from it, and finally how you can diagnose and fix the problem before it’s too late. 

The engine oil has the all-important task of maintaining lubrication between all the moving parts in the engine to minimize friction and also dissipate the heat. If there is less engine oil in the engine, the oil pressure also decreases and many intricate or small sections of the engine remain unlubricated. This can increase the heat between these components and eventually seize. Low oil pressure can also disrupt any oil pressure-dependent systems like variable valve timing which would result in poor fuel economy or worse. Low oil pressure can be caused by a worn oil pump and low oil levels and low oil levels can be a result of leakage and/or oil burning. 

Apart from low oil, bad or incompatible engine oil viscosity grade or type can also severely damage the engine beyond repair. Most engines are designed to run on a specific engine oil viscosity according to the climate conditions of the region. If you deviate from these recommendations and let’s say you were to add thinner engine oil, the engine would perform well on cold startup. But with higher engine temperatures, the engine oil would get even thinner which would affect its high-temperature performance. Similarly, adding thicker oil can cause trouble during cold startup as it can starve the engine of the necessary cold startup lubrication it requires. Adding improper engine oil types can also cause issues. Engine oils are designed with specific engines in mind and have additives that cater to particular engine conditions. 

Failing to replace the engine oil for prolonged mileage or multiple years is also extremely bad. Engine oil can last only so long before the additives wear out and the oil becomes acidic. Acidic oil can eat away metal and rubber gaskets and seals within the engine causing leaks and premature failure of the engine. You must change engine oil every year or when you meet the mileage for your particular engine oil type. Make sure you replace the oil filter as well during every oil change. 

Diagnosing/Fixing: It is easy to check low oil levels in your engine. 

• Always check engine oil level either when the engine has been off for 10 - 15 mins or before it is started. Examine the oil dipstick reading.  
• If it is below the min mark then you need to add engine oil asap. Make sure you add the right type and viscosity of oil recommended by your vehicle manufacturer. 
• If you are unsure of what the previous car owner used in a second-hand car. Completely drain the existing oil and add the recommended engine oil. 

Engine overheating is most commonly a result of failure in one or more components in the cooling system. This may be caused by leakage or a faulty component within the cooling system 

• A bad thermostat stops coolant flow which is one of the leading causes of engine overheating. 
• Leakage within the radiator or hoses or in the heater assembly can reduce the coolant level and cause engine temperature to rise. 
• The broken water pump can cut the supply of coolant to the engine block causing engine overheating. 
• A faulty radiator cap or improper coolant flush can introduce air pockets inside the engine which may cause the engine to overheat.
• Similarly, only adding water and no antifreeze in the cooling system can cause the water to boil which introduces steam within the engine block, creating hot spots and making the engine run at higher temps.
• Bad coolant can also be responsible for overheating and other issues like internal engine corrosion which can also speed up engine failure and make it more susceptible to cracking. It is important to change the coolant according to the manufacturer-recommended intervals and use the right coolant type which is usually indicated by its color. 
  

The engine can overheat for several reasons apart from just cooling system failure. For example, a faulty catalytic converter or other exhaust system restrictions can make the engine work harder and eventually run hotter. Incorrect ignition timing, low fuel pressure, and overly restrictive air intake system. 

Overheating engines can result in a complete seizure since metal expands as temperatures increase. This can be catastrophic for the engine and in most cases is unrepairable. 

Diagnose/Fixing: If you notice your engine is overheating, there are a few checks you can perform to identify the root cause. 

• First, check the amount of coolant present in the coolant reservoir or radiator (do this with the engine off and cool to touch). 
• Next assess the condition of the coolant. An easy way is to check the color of the fluid. A dull or dark color indicates the coolant is old but not necessarily bad. If you see debris then you likely need to perform a coolant flush. There are more accurate ways of determining coolant conditions and you can read about them in how to flush your car’s coolant. 
• Inspect the water pump. If you notice these symptoms of water pump failure, then you may need to replace the pump. 
• If you have a low coolant level, then you need to find the leak spot. Check all the radiator and heater hoses, thermostat gasket, and all connection points. A cooling system pressure tester can help identify weak spots. 
• Replace all components that are old or worn out. 

Detonation occurs when there is an uncontrolled explosion in the cylinder due to excessive pressure and temperature and is evident from a knocking sound coming from the engine. Many engines suffer from light detonation but that does not cause damage and is usually due to lower octane fuel or slightly higher engine temperatures. However, heavy or prolonged knocking (detonation) can cause damage to the piston, piston rings, cylinder head, rod bearings, head gaskets, and other engine components. Severe detonation can occur due to engine overheating, improper ignition timing, oil in the combustion chamber, or a malfunctioning EGR valve. The EGR system helps reduce the combustion temperatures which on failing can cause increased NOx emissions and detonation. 

Diagnose/Fixing: 

• Modern cars have a knock sensor in the engine that can detect severe detonation and the ECU will retard ignition timing and/or add more fuel to stop the detonation. So if the knock sensor is bad, you can continue to have detonation. 
• The faulty EGR valve may also be the reason for detonation, so check the valve and EGR lines for damage. 
• If your engine is already suffering from overheating then start by fixing that first as mentioned in the previous section. 

Often when engines are rebuilt, reassembled, or major components are serviced there is a definite chance of human error like under or over-torqued bolts, failure to lubricate and clean parts, improper seal, or gasket placement, timing belt misalignment, etc. that can have serious consequences on the engine. In such cases, the engine can be under excess load or stress which can break various engine components and wear them out faster leading to premature engine failure. In case of improper timing belt servicing in an interference engine, the cam and crankshaft can be out of sync which causes the piston and valves to collide and completely destroys the pistons, connecting rods, cylinder walls, and intake and exhaust valves. A newly rebuilt engine or a low mileage engine can be susceptible to such fate especially if the engine has not followed the appropriate break-in period or procedure. To avoid engine problems in a new engine, make sure you follow the right break-in period and process as mentioned by the manufacturer. A similar procedure is applied to rebuilt or new transmissions, drivelines, and brake components. 

Diagnose/Fixing: if you have a new vehicle/engine or one that recently underwent major engine service then you need to adhere to the recommended break-in period to avoid such issues. However, if the engine is improperly rebuilt, it will eventually fail due to one or more causes so the only thing you can do is have your engine serviced by a reputed garage or trusted mechanic. If you have an older or high mileage engine, you will most likely not have issues due to misassembly. 

Hydro-locking happens when an engine sucks up water and then tries to compress it leading to catastrophic engine damage or failure. Hydro-locking is common in areas where there is heavy rainfall and the vehicle is driven through deep puddles and ingests water into the combustion chamber. Since water is incompressible, the piston cannot move to its TDC (top dead center) if the amount of water is greater than the space that’s left and this causes the connecting rod to bend or break, induces immense stress on pistons, con rods, and the main bearings and leads to failure if the engine is driven in such conditions for long at high RPMs. 

Diagnose/Fixing: A compression test can help you find the cylinder with hydro-lock as it will show lower compression readings than other cylinders. In most cases, hydro-locked engines can be repaired depending on the extent of the damage but will require engine disassembly and replacement of broken components and the cost will certainly be high. To avoid this situation altogether, do not drive through deep puddles or very heavy rainfall.