What is engine coolant?
Engine coolant is a water and antifreeze solution. Because water has good properties as a coolant, antifreeze is used in internal combustion engines and other heat transfer applications, such as HVAC chillers and solar water heaters. The purpose of antifreeze is to prevent a rigid enclosure from bursting due to expansion when water freezes.
As the coolant is moved around the system by the water pump, it passes through two main components:
- Radiator - The cars air intake is used to dissipate heat (which is easier across a larger surface area, higher fin density and thicker radiators - much like in PC water cooling). This is able to keep the engine coolant cool.
- Engine Block - This is the main part that the coolant is designed to wick away heat from, by flowing through engine hot spots and allowing the heat to transfer from the engine oil to the coolant as well in the process.
What exactly are all of the disadvantages to running an engine when the engine coolant becomes too low?
Just to clarify, there are no tangible advantages other than saving a tiny amount of money on engine coolant. As you will see, you should never do this due to the knock-on effect that it can cause.
Depending on the make and model of your car some of these may not apply, but in general:
- Water pump running dry - They will destroy themselves very quickly without water in them as they are not designed to run without lubrication and sufficient resistance (much like the pump in a water cooled PC).
- Overheating - this is the main disadvantage, but this can cause a huge knock-on effect in terms of causing other damage within the engine. These include but are not limited to the following:
- Seized piston - The piston will expand marginally due to the heat. As the engine uses such fine tolerances, this expansion can be enough to make the piston rub hard on the cylinder casing and make the crankshaft grind to a halt! This will be very expensive to fix.
- Hole in the engine block - Realistically however, a lack of coolant will not cause a hole in the block. It could be caused from a thrown rod, which occurred because the piston in the engine seized during operation.
- Warping of head(s) - This can cause the head gaskets to lose integrity.
- Interior car heater will lose functionality - The heater functions based on the engine coolant, as seen in the diagram above.
- Transmission failure - In some cases the transmission fluid cooler is internal to the radiator, meaning that a lack of engine coolant can not only cause the engine to overheat, but also the entire transmission.
- High pressure in hoses - Radiator/Coolant hoses can burst due to the increased pressure in the cooling system.
- Cost - To fix the damage already done to the engine at this point, it will be very expensive and you could probably justify buying a new used car instead!