Is Your Car Overheating or Leaking?


When faced with the warm Australian summer months and the possibility of stop and go traffic, an overheating radiator is not uncommon especially in older cars or poorly maintained vehicles. Although most people look at the cooling system of their vehicle as relatively meek, the proper maintenance is a key factor in avoiding overheating problems both in modern and vehicles.   Radiator function is critical to the engine’s ability to remain at a specified operating temperature. Without the radiator, the engine would quickly over heat and metal parts like the crank shaft, would seize up and destroy the engine.  I have listed below, some key reason for Engine/Radiators overheating and some simple processers that can be done to ensure that the problem is minimised and possibly prevent in the future.

Check your Cap

The radiator cap is more than a cap for your radiator; it keeps your engine cool by sealing and pressurizing the coolant inside it. It is designed to hold the coolant in the radiator under a predetermined amount of pressure. If it was not kept under pressure, it would begin to boil, and soon all the coolant would have boiled away. However, the radiator (or pressure) cap prevents this from happening by exerting enough pressure to keep the coolant from boiling. If your cooling system is under too much pressure, it can “blow its top”! To prevent this, the radiator cap has a pressure relief valve. The valve has a preset rating that allows it to take just up to a certain amount of pressure. When you turn the cap on the filler neck of the radiator, you seal the upper and lower sealing surfaces of the filler neck.

The radiator cap actually increases the boiling point of your coolant by about 25 C. How does this simple cap do this? The same way a pressure cooker increases the boiling temperature of water. The cap is actually a pressure release valve, and on cars it is usually set to 15 psi. The boiling point of water increases when the water is placed under pressure.

The pressure relief valve spring is compressed against the lower seal when you lock the cap. The radiator filler neck has an overflow tube right between the two sealing surfaces. If the pressure in the cooling system exceeds the preset rating of your cap, its pressure relief valve allows the lower seal to be lifted from its seat. Then the excess pressure (coolant, air) can squish through the overflow tube to the ground or the coolant reservoir.

When the fluid in the cooling system heats up, it expands, causing the pressure to build up. The cap is the only place where this pressure can escape, so the setting of the spring on the cap determines the maximum pressure in the cooling system. When the pressure reaches 15 psi, the pressure pushes the valve open, allowing coolant to escape from the cooling system. This coolant flows through the overflow tube into the bottom of the overflow tank. This arrangement keeps air out of the system. When the radiator cools back down, a vacuum is created in the cooling system that pulls open another spring loaded valve, sucking water back in from the bottom of the overflow tank to replace the water that was expelled.

Clean your Radiator

Excessive contaminants on both the inside and the outside of your radiator can cause a severe drop in cooling efficiency. To clean the outside of your radiator, simply apply a spray on degreaser liberally to the exterior of your cool radiator and rinse thoroughly with water. Flushing your coolant system is also a good way to prevent mineral and rust deposits on the inside, and should be done regularly with every coolant change. To flush your radiator, simply open the valve on the bottom of your radiator and drain the coolant from the system. With the engine running and the heater set to max, refill the system with water and allow it to drain as before. Once fluid comes out clear, begin refilling your cooling system with coolant, bleeding air as detailed above, and close the valve once fluid draining out is the color of your coolant. Always remember to use distilled water if diluting your own coolant, as tap water will cause mineralization and reduce cooling efficiency.

Simple maintenance can do wonders for the cooling ability of your radiator. Clean coolant in a properly sealed and pressurized system, combined with a clean radiator that can efficiently transfer away heat are the key points to a healthy cooling system. By maintaining these key points, your cooling system should remain healthy for years to come.