How to Check for Water in a Diesel Fuel Tank

Water and diesel are often found together, but they’re a bad mix. Excessive amounts of water in your fuel promotes the growth of algae and can corrode the steel tank. This has the potential to cause major damage to engine components, resulting in costly and extensive repairs. While it’s common to find small amounts of water in your diesel tanks, it’s an issue that you should keep your eye on. In this article we’ll go over how to check for water in diesel fuel tank and what you need to do to keep your vehicle in top condition.

Why There’s Water in Your Diesel Tank

While it’s true that diesel and water are a bad mix, it’s common to find small amounts of water in your diesel fuel tanks. There are three main sources of the water in your fuel tank:

  1. Condensation. Diesel is a highly stable fuel source that produces relatively little vapour. The lack of high pressure vapour in diesel tanks means there is plenty of headroom for air to accumulate. As the ambient temperature changes, the tank draws in humid air that collects as condensation on the walls. Over time this condensation can cause significant buildups of water in your diesel tanks.

  2. Handling. Water is often introduced into diesel tanks while filling and handling the fuel. Service stations are usually careful to separate water from their diesel while in storage, but it’s still possible to transfer water into your vehicle when refilling from a contaminated tank.

3. Tank and filler leaks. Leaks in your tank, filler cap or fuel filler lines can introduce water and other contaminants into your tank.

Signs There’s Water in Your Diesel

It’s common to find small amounts of water in your diesel tanks. If the concentration is low then it won’t create an immediate problem, and large droplets of water will usually be dealt with by your water separator. However, excessive amounts of water in your diesel promotes the growth of bacteria and corrodes the steel tank. Together, these two things can contaminate the fuel and scour your injectors. Eventually, this will destroy your injectors, fuel pumps, diesel tanks and damage core components in the engine.

There are a few key symptoms of water in your diesel tanks to look out for:

  • A loss of power

  • Difficulty starting

  • Erratic idle speeds

  • Acceleration lag

  • Unusual exhaust such as white smoke

How to Check for Water in Diesel Fuel Tank

If you’d like to avoid costly diesel repair service due to water in the system, it’s important to keep an eye on the fuel in your tanks. Your mechanic will perform their own tests to ensure water isn’t collecting in your diesel, but there are a few things you can do  between servicing appointments:

  • Checking the water separator. Most diesel vehicles include a water separator as part of the fuel system. Your mechanic will inspect and empty the separator during regular diesel servicing appointments, but you can keep an eye on it yourself to make sure it’s not collecting large amounts of water.

  • Inspect the diesel tanks. One of the easiest ways to check for water is to open your tanks and have a look inside. An experienced mechanic will be able to spot water contamination and the presence of microbes simply by the look and smell of the fuel.

  • Sample the fuel. Diesel that’s contaminated with water is noticeably darker than usual. Healthy diesel is clear and light coloured, although some manufacturers add coloured dyes to their fuel. Diesel that’s noticeably dark or cloudy can indicate that there’s water in the system.

  • Water testing chemicals. Your diesel mechanic may use a water testing product that quickly and easily indicates the presence of water. These products change colour when they contact water, making it simple for mechanics to spot contaminated fuel.

Don’t Leave it to Chance, Ask KS Mobile Diesel to Service Your Equipment!

Water in your diesel tanks can quickly turn from a common problem to major repairs. If you’d like to avoid that outcome, it’s important to book regular maintenance appointments and talk to your diesel mechanic about any concerns you have.

KS Mobile Diesel is a specialist mobile diesel mechanic based in Caboolture. Our team comes with decades of experience that allows us to tackle even the most complex issues. We’ve got the right equipment to quickly diagnose and remove water from diesel tanks, ensuring your engines are always protected from unnecessary damage. Contact us online to book an appointment, or phone us on 0403 524 804 if you need our emergency breakdown service.

Request a quote

Book an appointment or give us a call to discuss how we can help!