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What's a head gasket? And why does it cost so much to fix?

This expensive car repair is maddening. Here's why.

Brian Cooley Editor at Large
Brian Cooley is CNET's Editor at large and has been with the brand since 1995. He currently focuses on electrification of vehicles but also follows the big trends in smart home, digital healthcare, 5G, the future of food, and augmented & virtual realities. Cooley is a sought after presenter by brands and their agencies when they want to understand how consumers react to new technologies. He has been a regular featured speaker at CES, Cannes Lions, Advertising Week and The PHM HealthFront™. He was born and raised in Silicon Valley when Apple's campus was mostly apricots.
Expertise Automotive technology, smart home, digital health. Credentials
  • 5G Technician, ETA International
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Brian Cooley
CNET

I hate head gaskets.

That may seem like an impractical statement about a part that allows the two halves of your engine to work together, but it's a part that fails spectacularly, expensively and all too often in an era when little else fails on modern cars.

The head gasket is a piece of thin material with a lot of holes in it. 

head-gaskets

Head gaskets are thin wafers of material that seal engine blocks to cylinder heads. They contain pressure from combustion, oil and coolant to keep each in its own lane.

 Victor Reinz

It seals the engine head, where the valves reside, to the engine block where the pistons live. It prevents compression, combustion, oil and coolant from escaping or mixing with each other in the channels running between the two major assemblies of the engine.  

Watch this: Head gaskets and why they cost so much

When even a small part of the head gasket is breached, or "blown," your car will run poorly -- if at all -- spewing white or blue smoke from the tailpipe and burning through a lot of oil, coolant or both. 

The repair is to replace the gasket entirely, which involves removing about half of the engine to get to it. And when you've invested the labor to tear down the engine that far you often address other things like valve reconditioning, timing chain replacement, water pump service, or intake and exhaust gaskets. That's why a head gasket job is seldom just that. It usually starts around a grand and can easily hit several thousand dollars. 

Easiest way to avoid this expensive nightmare? Get an electric car. They don't have engine blocks, cylinder heads or head gaskets mating the two. Problem solved.