October 12, 2026 · 5 min read
7 Signs of a Blown Head Gasket (and When to Replace the Engine)
White smoke, coolant loss, overheating? Learn the 7 signs of a blown head gasket, how to test for it, and when a replacement engine is the smarter choice.
The common symptoms
White exhaust smoke with a sweet smell, unexplained coolant loss, overheating, milky oil, bubbles in the radiator or overflow tank, rough running when cold, and loss of compression on one or two cylinders.
How to test
A combustion leak (block) test on the coolant, a compression test and a leak-down test confirm the problem. A cooling system pressure test can also show external leaks.
Repair or replace?
On a healthy engine caught early, a head gasket job is often worth it. If the engine overheated badly, the head may be warped or the block cracked, and machine work adds up quickly. In that case a good used replacement engine can be cheaper and faster.
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