Fig. 6.5. Measuring the density of the coolant with a hydrometer with a float
In mid-latitudes, the coolant protects the car engine from frost down to -30°C based on Ford antifreeze, which corresponds to 50% of the mixture. If water was added to the expansion tank, this means that the concentration of antifreeze in the coolant has decreased. To determine the frost resistance of the coolant, a hydrometer is used to measure the density of the coolant (Fig. 6.5). The following rule can be used: adding 3/4 l of antifreeze to the cooling system increases the frost resistance of the coolant by 10°C.
The total volume of coolant to be poured and the proportions to ensure frost resistance down to –30°C are given in Table 6.1.
WARNING
Different antifreezes provide different levels of corrosion protection and compatibility with light metals. Choosing the wrong antifreeze will result in significant repair costs. If you cannot completely replenish the old antifreeze, it is better to completely replace the coolant.
30,000 km 2 years
SEQUENCE OF WORKS
1. To relieve pressure in the cooling system, open the expansion tank cap. Be careful when working on a hot engine - there is a risk of getting burned!
2. Place a clean container under the radiator and loosen the clamp securing the lower radiator hose or unscrew the plug on the lower radiator tank. Remove the coolant hose from the pipe.
3. To help the coolant drain better, remove the cap from the expansion tank. Drain approximately 1–2 liters of coolant and cover the container with the drained liquid.
4. Install the lower radiator hose (use a new clamp if necessary). Tighten the drain plug securely.
5. Add the required amount of antifreeze to the expansion tank. Fill the remainder with the drained coolant. Replace the expansion tank cap.
PRACTICAL TIPS
Do not add cold water to the cooling system of a hot engine
If your engine cooling system has lost too much coolant during a trip, do not add cold water to the expansion tank under any circumstances. A hot engine can suffer thermal shock from adding cold water, and in extreme cases, the cylinder block can be torn or the cylinder head can be deformed. In this case, your engine cannot be used any more, since the cylinder head gasket will not be able to fit tightly to the cylinder block, and the coolant will leak out of the block or mix with the engine oil, resulting in an emulsion that will damage the engine. Therefore, wait for some time for the engine to cool down, and only then add water. In any case, you should contact a specialist to determine the cause of the coolant loss.