FAQ : How to Diagnose a Blown Head Gasket

FAQ : How to Diagnose a Blown Head Gasket


We get this question more often than not unfortunately, especially for those customers running a air-to-air intercooler or another sort of heat exchanger in front of their radiator and air conditioner condenser. When you add such parts and performance goodies to your vehicle, it’s not always to the benefit of your car, and the ability to cool down your engine will be negatively impacted by the addition of such modifications.

White Smoke from Exhaust

One of the more easily identifiable symptoms as excessive white smoke may billow out from your tailpipe and smell sickly sweet like cotton candy. If your engine has overheated enough to warp the head or the seal to your combustion chamber, coolant may leak into the combustion chamber and burn in the process, leading to the sweet burning smell of coolant.



If you notice lots of white smoke from your exhaust, try starting the car and having someone rev it while you stand behind the car. Does it smell sweet? Check your local mechanic for a quote on a leakdown test.



What is a leakdown test?

A leakdown tester is also called a block tester, in which a aspirator bulb pulls fumes from the inside of the radiator to determine the level of combustion gas in the coolant and cooling system. This method is the easiest and most foolproof way to test your engine and the overall health of your longblock and combustion chambers.

Easily the cheapest and easiest method for checking your block, you may also opt for a four-gas sniffer analyzer ( ones found at smog stations or dyno facilities ) to test the radiator for traces of hydrocarbons.

Why is my car overheating?

Your car can overheat from a variety of issues but if your car was in good operating condition before it started overheating, try to remember when it began to overheat. Did you take a long trip? Did you recently work on the car? Change or add any parts that may have affected the vehicle?

Your car overheating is due to any one of these issues.

  1. Poor Heat Transfer – Water Pump Malfunctioning or worn drive belt – Check your Drive belts and the last time your water pump was serviced.
  2. Thermostat stuck closed – Check the thermostat outlet hose to make sure that at a certain operating temperature, your thermostat is actually opening.
  3. Damaged Radiator – Check for damage or bending of fins, cores or other damage that may reduce cooling efficiency.
  4. Clogged or contaminated radiator – Check to make sure that nothing is clogging your radiator and preventing coolant from passing through it.
  5. Cooling fan does not operate – Check that your fans still turn on at operating temperature.
  6. Leaks or loose clamps – Make sure you aren’t leaking coolant and that your coolant levels are still sufficient.

Other Symptoms of a Blown Head Gasket

A milky Oil Cap or Radiator cap will definitely indicate that the 2 fluids in your engine that aren’t supposed to be mixing, in fact are. Check your cap frequently as just a test, or try smelling the oil on the cap to detect the familiar sickly sweet smell that oil and coolant create when mixing.




Milky Oil Dipstick

This one is straight forward as well, simply check your oil level and see if there looks to be any gunky yellow mixture or if the oil seems to be coagulating on the dipstick itself. Contaminated oil is very easy to spot and can often lead to a gunky deposit on the end of your dipstick.

Bubbling Coolant

Another sign of head gasket distress is the sign of bubbles passing through your radiator, to check for this remove your radiator cap and warm up the engine. When you rev the engine, you should see bubbles coming through the opening in your radiator cap.

Lack of Power

If your head gasket is leaking coolant into the combustion chamber, a lack of power will become very obvious as your vehicle is not operating on all cylinders (literally). Sluggish response or poor performance in coordination with white smoke is another sure fire tell to a blown head gasket.

Spark Plug Contamination

Coolant in or around the spark plug electrodes is a sign of advanced head gasket failure, if you have green coolant on your plugs your problem is severe and may lead to total engine failure if left unchecked.



Take a look at our selection of performance head gaskets, or simply shop our OEMSPEC replacement catalog for the replacement head gasket for the vehicle you need.