An engine coolant and an antifreeze are the same thing. It’s the one fluid that stays in a truck’s system through all seasons, protecting the engine from overheating in hot weather and from freezing up when the temperature drops. Maybe that’s why many operators don’t give it a lot of thought beyond the onset of summer or winter. Yet as we pointed out in a previous article, the coolant system requires more than just a seasonal check. A problem with the coolant system can spread to other parts of the vehicle and lead to costly downtime, which is why an inspection should be a regular part of your preventive maintenance program.

Start with a Visual Assessment

You can tell a lot about the coolant system simply from a visual assessment just by looking at it. Start by checking for leaks from loose hoses, clamps, and the radiator cap. It’s considered best practice to pressure check the system using a readily available pressure tester. If a change in pressure appears during the test, that may be an indicator of a leak in the system.

Make sure that the coolant is at the fill line in the sump. If the level of fluid is below the fill line, you are definitely losing coolant, and the only question is how. If the coolant system is not holding its pressure, you are most likely boiling off water. A coolant is typically a 50/50 or 60/40 mix of glycol and water (depending on the regional climate), and losing water will upset that balance. If you see streaming trails on the outside of the radiator cap, that is an easy way to tell if water is boiling off.

A visual inspection should include an assessment of the fluid itself. The dye in the coolant tends to leach into the plastic of the sump and impede clear visibility, so it is best to open up the radiator cap and look down into the fluid. The color of the coolant is simply a dye and serves no technical purpose. However, if you see brown in the fluid, that could mean rust is present, or that two different coolant types have been mixed. In either case, the system needs to be flushed and drained, and fresh coolant put in. If oil has entered the coolants system, it will be plainly visible as a layer on top of the fluid. Oil in the coolant is a bad sign. It usually means there is coolant in the oil system, too, in which case both the coolant and the oil will need to be completely flushed.

Find a Leak on the Road? Just Add Water

Sometimes a driver may discover a leak on the road. When that happens, there are any number of off-the shelf products you can pour into the system that purport to help stop the leak. However, we don’t recommend that for two reasons: you’re not really fixing the leak at its root cause, and you’re introducing a foreign additive that is going to cause an imbalance in the fluid.

A better (and cheaper) temporary solution is simply to top off the system with water. You may diminish the protection properties of the coolant to a small degree, but it is better than bringing in another chemical, and it should buy you enough time to get to your maintenance shop and get the system fixed.

The important thing is not to mix coolant types. Coolants come in a variety of formulations, whether conventional, fully formulated, hybrid, or a full extended life coolant. If you’re not certain which type you’re using, topping it off with water temporarily is your best quick-fix option. Use bottled water or distilled water – don’t use water from a tap or a hose, which likely has impurities in it.

Keep your Water and Glycol in Balance

One essential tool in your coolant maintenance kit is a refractometer. That is what professional labs use to check the balance of glycol and water and find the freeze point. It is very easy to use and readily available on Amazon or from your lubricant supplier. The reading on the refractometer will help you determine if you need to adjust the water or glycol concentration levels to achieve the appropriate freeze and boiling points for your operating environment and conditions.

Chevron offers a full line of coolants for heavy duty vehicles, both on- and off-highway, as well as our handy Cool Tools Maintenance Kit that includes a refractometer, test strips, sampling tools and more. We also have coolant experts on hand to answer any questions you may have. Remember, a small investment in time and the right tools can save you on costly repairs and downtime in the future. Keep an eye on your coolant all year ‘round.