Engine Cooling

The cooling system used on all Western Star vehicles is a pressure type system. This raises the coolant boiling point, permitting higher operating temperatures. The coolant supplied in your vehicle will be a 50/50 mix of antifreeze and water, giving protection down to –35°F(–37°C). It is recommended that an antifreeze mixture be used at all times, as, in addition to providing frost protection, it is a more effective coolant, and has a higher boiling point than tap water.

Over-concentration of antifreeze or coolant conditioner can cause silicate to precipitate out of the coolant, forming silica gel on cooling system heat transfer surfaces (fuel coolers, oil coolers, radiators, and heater cores), resulting in reduced coolant flow and overheating.

Hard water (with high levels of calcium and magnesium ions) encourages formation of silica gel. Do not use softened water as the salt used to artificially soften it is corrosive. Most engine manufacturers prefer the use of distilled or de-ionized water to reduce the potential and severity of silicate dropouts.

Never exceed a 60/40 antifreeze-to-water ratio. If the level is low, add a 50/50 antifreeze solution to maintain solution concentrations. Note that checking the engine coolant level is part of the pretrip inspection. See Safety Precautions for more information.