Is your antifreeze eating your engine?

Posted on March 12th, 2019 by Rob Marshall

Is your antifreeze eating your engine?

As we start to look forward to spring, you may think that antifreeze does not matter any more. Indeed, the coolant within your engine has many properties. Yes, it cools the engine but it also possesses an anti-corrosion property. These additives diminish gradually over time, until either corrosion, or decomposing coolant, causes a blockage and the first you know about it is an overheated (and, possibly, ruined) engine.

DIY check
To check the antifreezing properties of your coolant, you can use an old-fashioned hydrometer but checking the concentration of coolant and water does not assess the anti-corrosion element.

To do that, you will need to have a rough idea of how to operate a multimeter. They look complex but are not that tricky to master. However, first, the engine must be at its normal operating temperature but be very careful, when removing the cap from the cooling system’s expansion tank. If the engine is too hot, the loss of pressure can cause the coolant to boil and, more seriously, you could be burnt from escaping steam, so take great care. If you are unsure, ask a garage to do the following test for you.

1. Turn on the multimeter and select either 20 volts, or millivolts, on the scale.
2. Place the ‘negative’ wire on the battery negative terminal, or on the bodywork.
3. Place the ‘positive’ wire into the coolant.
4. Note the reading. If more than 0.6 volts (or 600 millivolts) are noted, the coolant requires replacement. The pictured reading is 177.9 millivolts (0.177 volts), indicating that the anti-corrosion properties on this engine are in good health.