To tell if a head gasket is blown, look for these key symptoms:
- Engine Overheating: A repeatedly overheating engine is a common early sign. This happens because a blown head gasket can allow coolant to leak into the combustion chamber or oil passages, reducing coolant levels and impairing engine cooling. Watch for high temperature gauge readings, steam from the engine bay, low coolant levels, or cooling fans running excessively
- White Smoke from the Exhaust: Thick white smoke with a sweet smell coming from the tailpipe indicates coolant leaking into the combustion chamber and burning with the fuel. This smoke usually persists even after the engine warms up
- Milky or Contaminated Oil: Check under the oil filler cap or on the dipstick for milky, frothy oil that looks like a milkshake. This means coolant has mixed with the engine oil, which can cause serious engine damage
- Loss of Coolant Without Visible Leaks: If coolant levels drop frequently but you don't see puddles under the car, coolant may be leaking internally through the gasket into the engine
- Bubbles in the Radiator or Coolant Reservoir: Continuous bubbling in the radiator or coolant overflow tank while the engine runs suggests exhaust gases entering the cooling system through the blown gasket
- Poor Engine Performance and Misfires: A blown gasket can cause loss of compression in cylinders, leading to rough idling, misfires, loss of power, and difficulty starting
- External Oil or Coolant Leaks: Sometimes leaks can be seen around the cylinder head or engine block area near the gasket
Additional diagnostic tests include:
- Inspecting spark plug holes for coolant by pressurizing the cooling system and cranking the engine (with ignition disabled) to see if coolant appears
- Using a chemical tester to detect exhaust gases in the radiator coolant, which confirms a gasket leak
- Compression testing cylinders to find adjacent cylinders with low compression, indicating gasket failure between them
If you notice these symptoms, stop driving and have a professional mechanic inspect your vehicle promptly to prevent severe engine damage
