Adding Coolant

A noticeable loss of coolant indicates a fault or damage. Coolant is not consumed, and in a closed cooling system it cannot evaporate. Small amounts of coolant may be forced past the cap only if the engine overheats.

If coolant loss is constant, check the cooling system for leaks as described later in this chapter.

If the threaded expansion tank cap must be opened while the engine is hot, there is a high risk of scalding. Proceed with caution:

Wearing gloves or using a cloth, slowly turn the cap one turn to allow excess pressure to escape from the system. Only then remove the cap completely.

If only distilled water is added, the coolant will gradually become diluted. Therefore, add concentrated antifreeze whenever possible.

Do not fill above the "max" mark (see previous section). Coolant expands when heated, and excess will be expelled from the system.

Small amounts of coolant can be added to the expansion tank with the engine either cold or warm.

If coolant loss is significant and the engine is hot, never add cold water to the expansion tank. Thermal shock may warp the cylinder head or crack the cylinder block.