The Symptoms and Causes of a Blown Head Gasket

  • October 23, 2023
Smoke comign from the engine Smoke comign from the engine

Perhaps you’ve noticed excessive white smoke coming from your exhaust pipe, or maybe you received a worrying professional diagnostic. Either way, you’re anxious that your vehicle might have experienced head gasket failure. Your concerns are valid — head gaskets are vital to engine health. 

So before you keep driving, take our crash course in blown head gaskets. Learn everything you need to know about these components — from what they do and how they fail, to diagnosing problems and helping to prevent them in the future.

What Does the Head Gasket Do on a Car?

You’ve probably heard of head gaskets before, but what exactly are they, and what do they do for your engine?

Head gaskets are seals that get sandwiched between your vehicle’s engine block and cylinder head(s). Their job is to keep the combustion chambers sealed, which allows for proper compression. They also prevent oil and coolant from mixing. Simply put, these unsung heroes make everything work and prevent your engine from destroying itself. All the while, extreme heat, pressure, and temperature fluctuations try to rip them apart.

Fortunately, head gaskets are hardy. Though they used to be made of materials like asbestos and copper, or silicone and graphite, most modern head gaskets are constructed from multiple layers of steel. This design enables head gaskets to withstand more pressure, heat, and thermal expansion than ever. 

What Causes Head Gasket Failure?

Everything undergoes failure after enough time and use, but factors like these can cause head gaskets to fail sooner rather than later:

  • Poor Maintenance: A lack of cooling system maintenance can lead to overheating — the most common cause of head gasket failure.
  • Overheating: When your engine overheats, the cylinder head or engine block can warp or expand. When this happens, your head gasket may no longer seal properly.
  • Pre-Ignition: Sometimes known as detonation, pre-ignition occurs when air and fuel ignite in the combustion chamber before it is supposed to. When this happens, combustion temperatures and pressures rise. Higher combustion temperatures and pressures can compound overheating and further test the head gasket(s).
  • Installation Errors: If you’ve recently had your engine rebuilt or replaced, it’s possible that your head gasket was installed incorrectly. Don’t be too hard on the installer, though — head gasket installation can be tricky. Simply over tightening cylinder head bolts can lead to head gasket failure! 

Common Signs of a Bad Head Gasket 

Want to learn how to test for a bad head gasket? If your car is suffering from this issue, it’ll probably exhibit one or more of these symptoms:

  • Coolant Loss: Keep an eye on your coolant levels — a significant drop is a red flag. If you’re constantly topping off your coolant but can’t find any leaks, it’s nearly always a sign that you’re burning coolant.
  • White Smoke from the Tailpipe: Some white smoke from the exhaust pipe of a cold engine is normal.  However, if your exhaust starts spewing thick, white smoke after the engine has warmed up, it generally means that coolant is entering the combustion chamber — one of the main signs of a failed head gasket.
  • Engine Knocking: Blown head gaskets can lead to poor compression. Some head gasket leaks can contribute to combustion chamber deposits that can cause pre-ignition and an audible knocking sound. Ignition problems may also present themselves as unusual pinging or thudding sounds coming from your engine bay.
  • Milky Oil: Check your engine’s oil. If it looks like a milkshake (of any delicious variety), it’s generally a sign of coolant contamination, possibly due to a blown head gasket.
  • Overheating: If your temperature gauge consistently hits the red zone, it may be due to a bad head gasket.

Driving with a Blown Head Gasket — Yay or Nay?

Nay, we say! Driving with a blown head gasket is an exceptionally bad idea for your engine’s health. When head gaskets fail, coolant can mix with your engine’s oil and break it down. This results in more friction and heat, which are the nemeses of engine longevity. 

But will a car still run with a blown head gasket? Yes, in some cases. However, the loss of compression caused by blown head gaskets may lead to combustion chamber deposits which can lead to pre-ignition or detonation. This can harm many critical engine components. Left unchecked, a blown head gasket will nearly always result in severe engine damage and inflate your repair bill. 

Blown Head Gasket Repair Cost

Let’s talk cost. It’s not pretty, but we’ll give it to you straight. 

The best way to prevent further damage to your engine is to replace your head gasket. Unfortunately, doing so can be relatively pricey; according to Consumer Reports, replacing a blown head gasket can cost upwards a few thousand dollars. However, few repairs are more expensive than engine replacement, so it’s likely in your best interest to have your head gasket replaced ASAP. 

How to Prevent a Blown Head Gasket

Prevention is the name of the game. Here’s how you can help prevent your head gasket(s) from a premature demise:

  • Perform Regular Maintenance: Change your oil, replenish coolant when needed, and keep an eye on the temperature gauge. A well-maintained engine is less likely to suffer a head gasket failure.
  • Use Fuel with an Appropriate Octane Level: You’ve probably noticed that gasoline is organized by numbers like 87, 89, and 91 — these are octane ratings. The higher the octane, the less likely your fuel is to detonate before it should. Higher compression engines require higher levels of octane. Check the inside of your gas cap or your owner's manual for information on what octane level your vehicle requires.
  • Pay Attention to Warning Signs: Do your best to notice unusual symptoms like overheating, strange noises, or smoke from the tailpipe. Catching problems early can be easier on your engine and your wallet!

Don't let head gasket repair costs get you down. Your local Firestone Complete Auto Care can help you keep your car on the road with scheduled maintenance. We offer professional engine services, expert advice, and most importantly, peace of mind. Schedule your appointment today!

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