The Most Common Diesel Engine Overheating Causes and Symptoms

Diesel engine overheating can be the result of a number of conditions and causes. It’s always important to remember that if your diesel engine has overheated, the safest thing to do is turn off the engine immediately. As you don’t yet know the cause of the problem, you won’t know how severe the risks are or if there is irreparable damage to the engine, so it’s always better to be safe and wait for the engine to cool completely before investigation.

The reason for diesel engines overheating includes anything that limits the cooling system's ability to absorb, transfer or dissipate heat. Below we discuss some of the most common diesel engine overheating symptoms:

Coolant Leaks

Coolant Leaks are the primary cause of overheating in diesel engines and can be easily identified, as you will notice either a low coolant level or an excessive amount of bubbles in the coolant. This can be a result of engine components, such as the cylinder head, expanding due to excess heat. As a result of this particular degree of expansion, the gasket becomes unable to perform its designed sealing function. Unfortunately, this needs to be fixed by a professional, so it’s best to always take it to your local garage so they can determine the extent of the problem.

Damaged Cooling Fan

When cooling fans break, it causes the engine to overheat quite rapidly. Many fans get damaged due to electrical issues, so it may be the case that repairs are needed rather than replacements, depending on the issue. Again, it’s always best to leave it to the professionals to check it out and review the damage.

Blocked Diesel Injectors

Leaks or clogs in your diesel injectors could be the cause of your overheated engine. When your injection system struggles to release fuel, the engine will try to overcompensate, causing it to overheat. Modern diesel injection systems are extremely complex, therefore they should only be tacked by a diesel injection specialist.

Broken Thermostat

The thermostat in your car is essential for prevention of engine overheating. As it is a heat-sensitive component, it has a valve that opens and closes to regulate the engine temperature. If the thermostat is faulty it can’t determine when the engine is overheating, meaning it’s unable to initiate any cooling responses.

Faulty Radiator Hose

Overall, any disruption in the radiator’s function can cause diesel engine overheating. Coolant temperature is actually reduced within the radiator, so if the radiator hoses break or collapse it means that fluid can’t get to or from the engine without causing leaks. This type of leak is easily spotted and the hose can be replaced by a mechanic.

It’s worth bearing in mind that when a diesel engine overheats, it can result in further problems for other parts of the engine too such as; cylinder heads, gaskets, pistons and bearings.

Cylinder Heads and Gaskets

When the cylinder head becomes overheated it can crush the head gasket, therefore restricting the coolant flow to the cylinders. Sometimes the cylinder head can swell, distort or even crack as a result of this. In addition, it can also cause the head gasket to leak either compression between the two opposite cylinders, or possibly leak coolant into the cylinders.

Pistons and Bearings

As the engine rises in temperature, it can cause the pistons to swell and expand until they are exceeding the space. As a result, they can scrape the cylinders, causing damage to both the pistons and cylinders. Similarly, once the engine has overheated, it can negatively impact and damage the bearings and crankshaft.

Contact us with your engine number if you are currently experiencing any diesel engine-related issues and our team of experts will be happy to assist you.

Foxwood Diesel is a national distributor of Cummins spares and engine parts, as well as Mercedes, Volvo, Perkins, DAF and all major diesel vehicle manufacturers, with a wide range available for same-day dispatch. We have a dedicated team with over 70 years of experience between us, able to undertake highly effective reconditioning and rebuilding solutions. Please contact us to see if we can help you find the right part or solution.