What color is your coolant? (Part I)

What color is your coolant?

All cars have an engine cooling system. The purpose is to keep the engine from overheating due to the natural combustion process and to provide warm air inside your car on cold days. The water pump circulates coolant through the engine to pick up the heat. Part of it goes through the heater core inside the car, then through the thermostat, then back to the radiator where outside air is used to cool it back down via a radiator fan. The system is closed, which means the coolant keeps traveling around in the same path. The thermostat is a temperature-regulated, flow control valve used to maintain a certain temperature, which is around 195 degrees F on most cars.

You have to have a specific mixture of coolant and water for best results–usually about 50/50 in most cases. Coolant, also known as antifreeze, keeps the fluid from freezing in the winter time, hence the name. Even in the relatively temperate climate of Overland Park, Kansas, coolant also does not last forever. As it wears to its extreme limits it becomes acidic and begins to rust and corrode all the parts it comes in contact with, including the water pump, radiator and head gasket.

Recently we worked on this old 1970 MGB a customer bought a few years back (Photo 1).

Photo 1

The car is in pretty good shape and we have been repairing the many electrical issues created by the Lucas electrical system found in many British cars. Anyhow, the coolant had turned a light brown color and the customer did not feel any warm air from the heater during the few cool fall and spring days. The system was not low on fluid either, so no leaks. Also the temperature gauge read low and erratic, that is, the needle vibrated as you revved the engine up.

Check back next time for the process we used to coax this vintage heating system into the 21st century.