How Do I Know When to Change My Anti-Freeze?

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Mazda recently announced a project to significantly boost thermal efficiency in its engines. In a nutshell, these engines would be able to use more of the heat energy created by burning gasoline. The technology could lead to a significant cut in vehicle emissions. But at the same time, even with this breakthrough, Mazda’s engines would still be losing about 44 percent of the heat created to power them. It’s that thermal inefficiency that makes anti-freeze so important. Without it, or if your anti-freeze is too old, all that unused heat just continues to build up. Your engine can seize up if the temperatures get too high.

Fixing that can be an expensive proposition. Avoiding it can be as simple as following a few basic guidelines.

What is Anti-freeze?

Although many people use the words “anti-freeze” and “coolant” for the same stuff, the terms actually refer to two different liquids. Anti-freeze is what you add to water to get coolant. For our purposes, anti-freeze has two key active ingredients. The first is ethylene glycol, which increases the boiling point and reduces the freezing point of water. That way, the water won’t freeze when the weather gets too cold, and it won’t boil off when the engine gets too hot. Anti-freeze additionally contains special chemicals that help prevent corrosion as the coolant moves through the car’s cooling system.

It’s also worth noting that some manufacturers have begun offering anti-freeze based on a different chemical, propylene glycol. It’s much less toxic than ethylene glycol, which has a sweet taste that can be attractive to kids and pets. In fact, propylene glycol originally was developed as a food additive.

How Does the Coolant Cool the Engine?

Nearly all vehicles on the road today have liquid-cooled engines. In these cars, the cooling system is essentially a closed-off circuit. A vehicle’s water pump pushes the coolant through the system, which includes dedicated channels built right into the engine. As it goes, the coolant absorbs heat that’s being lost due to thermal inefficiency. The coolant also goes on to run through the radiator. There, the air rushing past the radiator reduces the temperature of the coolant. The liquid keeps circulating through the system like this as long as the water pump is pumping.

What Happens if My Engine Overheats?

As you may remember from school, heat causes things to expand. In an engine, for example, the piston heads can expand so much that they can’t move in the cylinders. This is bad enough on its own, but it can quickly get worse. Since the crankshaft can still be trying to spin with the top of the piston stuck, the rod that connects the crankshaft to the piston can break. A “thrown rod” can punch a hole in the cylinder wall and cause a much bigger one in your bank account.

Excess heat can cause cylinder heads to warp out of shape and damage the head gasket (which helps create a seal between the cylinder heads and engine block). The damage isn’t always limited to the engine, either. If the water pump continues operating without any coolant to pump, it can quickly burn out. Further, the engine-cooling system in some vehicles helps cool the transmission fluid as well. That means a failure in the first system could have an impact on the second.

When Should I Change My Anti-freeze?

The best answer to this question can be found in your car’s owner manual or routine maintenance schedule. There can be fairly large differences between different brands, too. For a 2018 Honda Accord, the automaker recommends changing the coolant after five years or 60,000 miles. But, according to the manual for the 2018 Ram 1500, its coolant can last up to 10 years, or 150,000 miles. A typical off-the-shelf Prestone coolant splits the difference with five-year/150,000-mile protection.

The issue isn’t so much that the anti-freeze loses its ability to cool the engine. It’s that the corrosion inhibitors start to degrade. If that happens, the components in the cooling system can begin to rust and can eventually fail.

Which brings us to another way to tell when it’s time to change your anti-freeze. When those special protective chemicals aren’t working, you’ll be able to see rust or sludge in the coolant if you look in the reservoir. This is usually a smallish, translucent plastic tank that you can locate with your owner’s manual. With a cool engine, just unscrew the cap and peek inside. The liquid can be a lot of different colors, but it shouldn’t have anything floating in it. Nor should it have an oily, sludgy look. Either situation will require changing the coolant and flushing the radiator. Sludge or oil in the coolant is more serious. That can be a sign that other vehicle fluids are leaking into the cooling system, so it should be checked by a mechanic.

By | 2018-06-19T15:49:19+00:00 June 15th, 2018|Maintenance|0 Comments

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