Coolant, also known as antifreeze, is a vital fluid in your car’s cooling system. It circulates through the engine to keep it from overheating. Over time, coolant can break down and become contaminated, leading to a number of problems. Knowing the signs of bad coolant can help you identify potential issues before they cause serious and expensive damage to your engine. In this article, we’ll cover the basics of how the cooling system works, what causes coolant to go bad, symptoms of contaminated coolant, and how to test and change it. Let’s get started!
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How Does the Cooling System Work?
The main role of the cooling system is to keep your engine running at the optimal temperature. Here’s a quick overview:
- Coolant flows from the radiator through passages in the engine block and cylinder head. As it passes through, it absorbs heat from the engine.
- The hot coolant then circulates back to the radiator where air flow dissipates the heat.
- This cooling process allows the engine to run around 200-220°F – hot enough to work efficiently but cool enough to avoid overheating damage.
- The water pump circulates the coolant while the thermostat controls its flow to maintain the right temperature.
- The radiator cap builds up pressure within the cooling system to raise the coolant’s boiling point.
Proper coolant levels and composition are critical to keep this system running smoothly.
What Causes Coolant to Go Bad?
Coolant breakdown occurs for a few different reasons:
Age
Like motor oil, coolant has an expected lifespan. The anti-corrosion additives become depleted over time and can no longer protect the cooling system. Coolant should be flushed and replaced every 2-5 years or 30,000-60,000 miles.
Overheating
Extreme overheating causes coolant to boil away, become acidic, and lose its lubricating properties. This stresses the water pump and corrodes the radiator and other components. Even one instance of overheating can accelerate coolant breakdown.
Contamination
Coolant contamination occurs when:
- Excess minerals build up from hard water
- Engine oil or transmission fluid leak into the system
- The wrong type of coolant is mixed together
This reduces the coolant’s effectiveness and compromises the entire cooling system over time.
Symptoms of Bad Coolant
Here are some common signs that your coolant may be contaminated or breaking down:
Changes in Color
Good coolant should have a bright green (for glycol ethylene) or orange (for Dex-cool) color. If it appears brown, rusty, or milky, contaminants are present.
Low Coolant Level
Coolant levels that repeatedly fall low indicate leaks in the cooling system. These should be addressed as soon as possible to avoid overheating.
Overheating Engine
If your temperature gauge is running hotter than normal, it could signify weak coolant that is low on anti-corrosion additives.
Corrosion Build Up
White or greenish deposits along the radiator, engine, and hoses point to corrosion. This reduces flow and the system’s effectiveness.
Sweet Smell
Ineffective coolant lets engine chemicals leech into the system. This can create a sweet, syrupy odor.
High Pressure in the Radiator
Excess pressure in the radiator can mean the coolant’s boiling point is too low. This allows bubbles to form which reduces its heat transferring abilities.
How to Test Coolant
To check the condition of engine coolant, you can utilize a few different methods:
Visual Inspection
Take a look at the color and clarity of the fluid in the radiator and coolant reservoir. It should be translucent and free of debris. Compare it to new coolant to see if the color has faded or changed.
Refractometer Test
Use an optical refractometer to measure the coolant’s freeze point and level of corrosion inhibitors. Coolant should have a freeze point between -30°F to -34°F when new. Higher levels indicate scale buildup and corroded additives.
Hydrometer Test
A hydrometer measures the specific gravity or density of the coolant. Draw a sample and compare it to the manufacturer’s specifications. Higher density readings signify contaminated fluid.
Test Strips
Dip test strips into the coolant to check its pH, alkalinity, nitrites, and other chemical properties. This can identify high acid content and the level of corrosion inhibitors remaining.
Take a Sample
Have a shop analyze a coolant sample if you need an in-depth report on its condition, contaminants present, and whether it still meets the manufacturer’s specifications.
How to Change Bad Coolant
Here are the basics steps to flush out old coolant and replace it with fresh fluid:
Mix the New Coolant
Mix distilled water with the manufacturer’s recommended coolant at the proper ratio, usually around 50/50. Only use coolant specifically formulated for your make and model.
Drain the Old Coolant
Open the radiator drain valve and cooling system drain cock to release all old coolant into a container. Make sure to collect any spills.
Open Relief Valves
Open the radiator cap along with any bleeder screws or valves to help the system drain completely.
Flush with Water
Refill the system with plain distilled water and run the engine to temperature. This circulates water throughout to rinse out old coolant clinging to passages. Drain and repeat as needed.
Refill with Fresh Coolant
Pour in the pre-mixed coolant until the system is full. Turn the heater on high and continue adding coolant as needed to bleed air pockets. Replace the radiator cap.
Inspect for Leaks
Idle the engine and inspect all hoses, seals, and connections for leaks. Tighten anything seeping fluid.
Check Levels
Allow the system to fully cool then check the coolant level in the radiator and reservoir. Top up as needed.
Conclusion
Catching cooling system issues early by identifying bad coolant can avoid extensive engine damage from overheating. If you notice any symptoms of contaminated or aging coolant, have it tested and changed right away. Following the manufacturer’s maintenance schedule for flushing and replacement will keep your coolant in top condition.
Here are some key takeaways:
- Coolant breaks down over time and should be replaced every 2-5 years.
- Look for changes in color, leaks, overheating, corrosion, and odd odors.
- Test coolant condition with devices like refractometers, hydrometers, and test strips.
- Drain, rinse, and refill the system completely to change out old coolant.
- Properly maintained coolant is vital for engine health and preventing expensive repairs.
Checking and changing coolant regularly is one of the easiest ways to extend the life of your engine. With a basic understanding of the cooling system and symptoms of bad coolant, you can keep your car running at peak performance.