Causes for Overheated Engine — When to Seek Help From Lynwood Cooling System Service & Repair

Did you know that the average gasoline combustion engine is only 22% – 28%  efficient? That means that 72% – 78% of the heat produced through combustion must be ‘managed’ or removed by the cooling system to protect the engine! Although efficiency increases with engine temperature, there is a limit to how hot an engine can operate before melting.

Most newer engines are designed with a normal operating temperature range of approximately 195° – 220°F. Consistent operating temperature:

  • Assures effective emission control
  • Maintains fuel efficiency
  • Assures peak performance


The recommended mixture of ethylene glycol:water is 50:50. This mix raises both the boiling and freezing temperatures of the fluid. While you can increase the ratio of ethylene glycol: water as high as 70:30, this does not produce theoretical increases in operating temperature in real life situations.

With the 50:50 mixture, a sealed system with the radiator cap rated at 15 pounds per square inch (psi), will allow an operating temperature of 265° before boiling over. A 70:30 mixture increases that temperature to 276°, which is higher than ‘normal’, and can cause damage to aluminum heads and overhead cams.

What to Expect if Your Engine Overheats

Initially, engine overheating will cause your engine to ‘ping’; losing power as the octane rating of the fuel is exceeded by the heat and pressure in the engine. Continued detonation will eventually damage the rings and pistons and rod-bearings.

Hot spots can develop in the combustion chamber, causing pre-ignition of fuel to develop from continued overheating. The hot spots can cause serious damage by burning through the top of pistons.

Stress caused by continual overheating can cause aluminum heads to swell, distorting an blowing the head gasket. If the head gets hot enough, the head gasket can crush! When the engine cools, leaks will be present from the loss of torque in the head gasket. Furthermore, overheating can cause your engine’s OverHead Cam (OHC) to seize and/or break.

When temperatures are high enough, older hoses and radiators can burst under the increased pressure. Serous engine damage can result by swollen pistons rubbing or seizing in their bores.

Sticking and scuffing of guides may also occur with exhaust valve stems under extreme temperature; which can cause a host of valve train problems. If coolant boils over, it can get in the crankcase which will damage the bearings and destroy the bottom end of your engine.

Some Common Causes of Engine Overheat

Anything that decreases the cooling system’s ability to operate can cause your engine to overheat. Any decrease in absorption, transportation or dissipation of engine heat can cause this problem. Some causes of coolant system decrease:

  • Low coolant level
  • Coolant leaking either internally or externally
  • Engine deposits causing poor heat conductivity
  • Defective thermostat that fails to open
  • Decreased airflow across the radiator
  • Fan clutch slippage
  • Cooling fan inoperative
  • Collapsed radiator hoses (especially the lower hose)
  • Defective water pump
  • Loose radiator cap

Never, ever ignore a HOT warning light! Most engines will suffer catastrophic damage with prolonged overheating. The best course of action is to turn the engine off and allow Lynwood Radiator Cooling System Repair & Service diagnose and repair the problem before driving further.