How to know cylinder head gasket is broken?
A blown head gasket is serious car trouble, but there are clear warning signs. Here's what to look for:
Classic symptoms of a bad head gasket:
- White smoke from exhaust (sweet smell - indicates coolant burning)
- Overheating engine that keeps happening
- Milky, frothy oil (on dipstick or under oil cap)
- Coolant loss without visible leaks
- Bubbles in radiator or coolant overflow tank
- Poor engine performance and misfires
- Oil in coolant or coolant in oil
Simple tests you can do: - Check oil cap for mayonnaise-like substance - Monitor coolant level regularly - Look for white steam from exhaust on startup - Use a block tester (chemical test that detects combustion gases in coolant)
If you suspect a blown head gasket, stop driving immediately! Continuing to drive can cause severe engine damage like warped heads or cracked engine blocks, which are much more expensive to repair.
As a mechanic with 15 years experience, I see head gasket failures weekly. Here's my diagnostic approach:
Definite Signs: - Constant overheating even after coolant refills - Oil and coolant mixing (creates a milkshake-like substance) - Compression loss between cylinders - Hydrocarbon test failure (combustion gases in cooling system)
The "Mayonnaise Test": 1. Remove oil filler cap 2. Look for creamy, tan-colored gunk 3. This indicates coolant mixing with oil
Other indicators: - Spark plugs fouled with coolant residue - Rough idle and misfiring - Loss of power, especially uphill - Coolant reservoir constantly needing refills
Cost reality: Head gasket replacement typically costs $1,500-$2,000 at a shop because it's labor-intensive (engine disassembly required). DIY is possible but complex.
Pro tip: If your car has multiple symptoms, get it professionally diagnosed ASAP. The longer you drive with a blown head gasket, the more damage occurs!