By far and away the most common symptom of an overheating Townace, is loss of coolant through the expansion tank.

Level of coolant drops in the filler tube, and increases in the expansion tank.
Usually the only indication that this is happening is a visual check on the coolant levels.

When the levels are checked first thing in the morning with a cold engine, the expansion tank level is above the full mark, and the level in the filler neck is low, and requires topping up.

This usually happens over a period of continued topping up through the radiator cap, and is an indication that the draw back mechanism is not working. This may be due to a faulty radiator cap, or leaks in the small hose from the radiator filler neck to the expansion tank, or the hose in the expansion tank itself.

Water is suddenly and violently expelled from the expansion tank.
It is important to remember that the expansion tank is outside the pressurised system. This means that it is possible for coolant that is in excess of 100°C, to be expelled from the pressurised system, into the non pressurised expansion tank. As a result of the drop in pressure, this coolant will boil and turn to steam instantly, giving the impression that a serious problem has developed, when in fact it is a normal occurrence. As water turns to steam, it expands more than 500 times its volume. A small amount of boiling water, will produce enough steam within the surrounding coolant to cause a big increase in pressure. The radiator cap reacts to this pressure and expels coolant out to the expansion tank. The expansion tank will then quickly fill and overflow. This may be the cause of the much-discussed "inexplicable coolant loss".

Water is violently expelled from the expansion tank, when the engine is under normal load.
This may happen at any time, even on journeys that are well within normal use.

It is an indication that the coolant is unable to loose the heat produced by the engine, and is boiling. When water turns to steam, its volume increases by more than 500%, and this is what causes violent eruptions of coolant from the system.

Water is violently expelled from the expansion tank, when the engine is cold.
This is usually a sign that the head gasket has failed in a fairly big way. The pressure from the cylinders is pressurizing the coolant, forcing it out of the filler neck.

Dave Bright, 25 Sep 2003.