Head Gasket

Seals the joint between the engine block and cylinder head, preventing combustion gases from leaking out and keeping coolant and oil from mixing with each other or entering the combustion chambers.

$1,000 – $3,000

Total Cost

As needed (not a scheduled maintenance item)

Replace Interval

Professional Only

DIY Difficulty

Do Not Drive

If It Fails

Overview

The head gasket seals the joint between the engine block and cylinder head. It's one of the most critical gaskets in your engine, sealing combustion gases, coolant passages, and oil passages simultaneously. Head gasket failure is one of the most expensive common repairs.

Parts Cost

$50 – $200

Labor Cost

$800 – $2,500

Failure Symptoms

White smoke from exhaust (coolant burning)

Critical

Milky/chocolate-milk colored oil on dipstick

Critical

Coolant level dropping with no visible leak

High

Engine overheating

Critical

Bubbles in coolant overflow tank

High

Sweet smell from exhaust

Moderate

Warning Signs to Watch

White exhaust smoke that doesn't go away after warmup
Coolant level dropping without a visible leak
Oil that looks milky or foamy on the dipstick or oil cap
Engine overheating repeatedly despite cooling system repairs

Common Causes of Failure

1Engine overheating (the #1 cause)
2Manufacturing defect in gasket material or engine design
3Age and mileage degradation
4Improper coolant maintenance
5Repeated thermal cycling (short trips)

Prevention Tips

Never drive an overheating engine — pull over immediately
Maintain proper coolant levels and flush on schedule
Fix cooling system issues (water pump, thermostat, radiator) promptly
Use the correct coolant type for your engine

When to Replace

Replace immediately if diagnosed — driving with a blown head gasket causes progressive engine damage. Coolant in the oil destroys bearings; combustion gases in the coolant cause further overheating.

Head Gasket by Make

Subaru

Subaru 2.5L EJ25 engines (1999-2011) are notorious for external head gasket leaks. It's a when-not-if repair. Budget $1,500-$3,000 and have it done proactively if buying a used Subaru.

BMW

BMW head gaskets rarely fail, but overheating from cooling system neglect is the #1 killer. The head can warp, requiring machine work plus gasket replacement for $3,000-$5,000.

Chevrolet

GMC

GM's 4.3L V6 and early LS-series V8 engines rarely have head gasket issues. The Duramax diesel, however, can develop head gasket failures from high cylinder pressures — a $3,000-$6,000 repair.

Honda

Honda head gaskets are generally reliable. The exception is the 2006-2009 Civic 1.8L, which had some head gasket issues related to overheating.