What Are The Most Common Diesel Engine Repairs?

Here, I am going to discuss the failures that occur outside the service schedule, whether within or beyond the manufacturer’s warranty period and those resulting from inadequate maintenance. It's important to understand that when you attempt to fix your diesel vehicle using online guides, these repairs are unlikely to work.

Car repairs, especially diagnosing diesel faults, should be left to professional mechanics who have years of experience and continuous training in diagnostics. Choosing the wrong part for replacement can be expensive, particularly if you fail to replace all the necessary components involved in the repair.

Fuel System

Fuel system issues caused by low-quality fuel are common, often leading to injector replacements. When an injector fails due to normal wear and tear, and no contamination is present, it's usually sufficient to replace the entire set of injectors. However, in some wear-related cases, the entire system might need replacement to ensure proper function.

If contamination occurs, repairing the system goes beyond just replacing injectors. Often, this leads to immediate injector failure. It’s crucial to understand the fuel's path in a diesel system: starting from the fuel tank, diesel passes through a fuel filter. While the filter blocks many contaminants, it doesn't stop all. Excessive contamination can breach the filter, especially if you use poor-quality or incorrect fuel.

After the filter, fuel moves to the high-pressure pump and then to the rail. Some fuel returns to the tank for cooling. Typically, a four-cylinder engine has one rail, while V6 and V8 engines have two. The rail distributes fuel to all injectors and any unused fuel returns to the tank. Contaminants can lodge in the metal components of the pump, rails, pipes, and tank, potentially causing rust and degradation. Once these components fail, the entire system must be replaced. No chemical cleaner can remedy this damage.

Exhaust Gas Recirculation Valves

Exhaust Gas Recirculation (EGR) valves and EGR coolers are subjected to extremely high temperatures as they work to reduce harmful emissions. Over time, carbon deposits can cause these components to stick, and if not properly maintained, they may fail prematurely. I strongly advise against so-called 'preventative maintenance' procedures like on-vehicle intake cleans, as they can damage critical parts such as EGR valves, coolers, turbos, and diesel particulate filters (DPFs). In some cases, this can even result in complete engine failure.

On average, I observe about 50 failures per year due to such methods. To prolong the life of your diesel engine, I recommend having a mechanic remove the entire intake, EGR, and cooler assembly for a comprehensive cleaning using an ultrasonic bath method.