To keep the radiator full at all times and eliminate the loss of coolant, car makers developed Car makers add a coolant recover tank and a new radiator cap The end result is that newer cars contain less coolant. Then, to keep the engine from overheating during driving, the cooling system circulates the coolant at a slightly faster rate and uses multi-speed radiator fans to remove more heat at the radiator. One way to speed up the process is to reduce the overall cooling system capacity so the engine is heating less coolant. The faster the engine can get up to operating temperature, the less fuel it uses. That’s because a cold engine requires a much richer fuel mixture. Car makers also decreased cooling system capacities to speed up warm up times again to improve mileage ratings. Cross flow radiators have a much lower height profile but are wider to provide adequate cooling.Īt the same time, car makers started installing more 4-cylinder engines to improve fleet mileage ratings. The down flow radiators were simply too tall to fit the modern swept hood designs. Car makers weren’t concerned about the low level because the remaining coolant would expand to fill the entire radiator once the engine warmed again.Īs car makers moved to more aerodynamic body styles with swept hood designs, they were forced to change radiator types from the traditional down-flow radiators to a cross flow design. So the next time the engine starts with cold coolant, the coolant level in the radiator is low. In older vehicles without a coolant recovery tank, the excess coolant gets dumped onto the pavement and is lost forever. Once cooling system pressure exceeds the cap rating, the cap releases coolant until pressure falls to less than the cap rating. Traditional radiators use a radiator cap that holds pressure until it reaches its preset pressure threshold. Two types of coolant recovery tanks pressurized and un-pressurized Above 40☏ it acts like all other liquids and expands with as it heats. As the ice warms from freezing 32☏ to 40☏, it shrinks. As water cools from 40☏ to 32☏ (freezing) it expands as the water molecules crystalize and turns into ice. It expands when heated and contracts when cold-but not at all temperatures. They’ve heard that water reacts the opposite way of all other liquids. They assume that since water expands as it freezes that it can’t possibly also expand as it heats. The people who say water doesn’t expand as it heats really don’t understand the unique thermal properties of water (engine coolant is approximately 50% water). The confusion about whether coolant expandsĭespite what other “experts” have stated, engine coolant does in deed expand as it heats up-all liquids do.
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