Checking Frost Protection

To check the frost protection of the coolant, you need a special instrument: a hydrometer. It measures the specific gravity of the liquid. Because different corrosion inhibitors have different specific gravities, the specific gravity of frost protection additives varies. For safety, subtract an additional tolerance of 2–3°C.

PROCEDURE

Draw a small amount of coolant from the expansion tank into the hydrometer.

The hydrometer floats at a depth that depends on the specific gravity of the coolant.

The scale shows the temperature down to which frost protection is provided.

Some frost protection testers have a pointer that indicates the degree of frost protection.

The illustration shows how the coolant concentration is determined using the frost protection tester.

Checking Antifreeze Concentration
In most cases, the coolant concentration is found to be insufficient. In that case, add antifreeze. As a rough guide, add approximately 1/4 L for every 10°C below the required protection level.

PROCEDURE

Remove the engine compartment undertray (see chapter Body Elements).

Place a suitable container under the vehicle.

Open the drain plug at the bottom of the radiator, or remove the lower radiator hose, and drain 1–2 L of coolant.

Reinstall the hose, or tighten the plug without overtightening.

Add the required amount of undiluted antifreeze, then top up with the collected coolant from the container.