How to Tell if Engine Coolant is Still Good

Updated February 21, 2017

If your vehicle has been acting up, smoking, running hot or smells funny, it's time to take a look under the hood. A good place to start is the coolant. The engine depends on coolant to keep it running properly. Read on to learn how to tell if engine coolant is still good.

Look at your coolant's color. Coolant is usually green when you add it to your engine. Some may be pink or another color. Both types are translucent, so you can see through them. When the coolant turns dark, or a different color than what was initially added, it has gone bad.

Use a hydrometer to test your coolants boiling and freezing points. Put the hydrometer into the tank. The meter draws out a small amount of the coolant to test. The higher the arrow on the tester, the better the coolant.

Watch for cloudy areas or areas that look like oil covered. These are both signs that the dirty coolant needs replacing.

Smell the coolant. If it smells like rubber, it is probably getting old. A normal coolant smells like sulfur.

Check for chunks of crystallized metallic build up on the sides of the coolant reservoir. When the engine is cool and there are signs of corroding, the coolant may not be working properly.

Make sure the coolant is the consistency of water. If it's gooey or thick, the system must be flushed and replaced with new coolant.


Coolant should be changed at least every other year. Also inspect the vehicle's cooling system for cracks or leaks.


Never leave old coolant lying around. It is a poisonous chemical. Take old coolants to a hazardous waste recycling center or auto repair shop to have it disposed of properly.

Things You'll Need

  • Hydrometer
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