Common Causes of Diesel Engine Failure

Written By JD Diagnostics & Diesel Repair on Oct 26, 2021

It might go without saying, but those of us who love diesel love it a lot. With the days getting shorter and the trails getting muddier, it’s a great time of year for diesel 4x4 enthusiasts. Of course, that notoriously wet Southern BC weather and rugged outdoor conditions are a part of the challenge and the fun of 4x4ing! But, with that being said, nothing will ruin a weekend of off-road fun faster than a dead diesel engine. 

To that end, we’ve compiled a list of some of the most common causes of diesel engine failure. This should be old hat for the more experienced grease-monkeys, but it doesn’t hurt to have a reminder, and for newer enthusiasts, this should provide a good oversight into some things to look for before heading up Vedder Mountain or out to Stave Lake for the day!  

Most Common Cause: Water Contamination 

This is a good place to start considering the kind of weather and trail conditions you’re going to find around Abby. There are a couple of ways that water can get into your fuel system including condensation of water in the fuel tank and loose fuel caps.  

The problem with too much water contamination over a prolonged period of time is that it has the potential to oxidize the system from the inside. As the rusty metal flakes off into the fuel system, the pieces cause abrasion from within and compromise your seals, valves and filters.  

Other Kinds of Impurities

Defective seals, blown head gaskets, and cracked cylinder heads

Water isn’t the only foreign contaminant that can ruin a diesel engine. If an engine has defective seals, blown head gaskets or cracked cylinder heads – all of which constitute serious damage on their own, glycol can make its way from the coolant and into the engine. 


A very small amount of glycol will cause the soot to coagulate and create a dump-out situation. This leads to sludge, blockage of filters, constricted oil flow as well as deposits – all of which are symptomatic of a diesel engine that is on the fritz.  

A layer of soot is perfectly normal in a healthy, well-used diesel engine. It is a byproduct of the combustion process and short of having an engine cleaned, an even layer of soot is nothing to worry about and will be present in all diesel engines that have spent time running.

Irregular concentrations of soot

What is troublesome, and can be a sign of an issue in a diesel engine, is irregular concentrations of soot. This could mean it is time for an oil change or worse. When there is too much soot or even sludge around the rocker boxes, valve covers, oil pan or dead deck it can signal a problem.  

Checking the engine for soot deposits and oil runs is a good idea before taking your vehicle out on the road or up any trails. What you want to see is a nice even smattering or layer of soot – when you notice clean drips or runs that can indicate a problem and we would advise you to take it into your mechanic for a closer look. 

With a little due diligence and some key signals to be mindful of, you can have confidence that your diesel will perform as expected the next time you’re up Sylvester Road or by Harrison Lake!

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