No, you should not drive a car with a cracked cylinder head. It is one of the most severe forms of engine damage. Continuing to drive risks complete and catastrophic engine failure, turning a repairable situation into one requiring a full engine replacement, which is exponentially more expensive. The crack allows engine coolant to leak into the combustion chambers and engine oil, leading to a cascade of critical problems.
The primary danger is coolant cross-contamination. When coolant enters the combustion chamber, it can cause hydro-lock—where the incompressible liquid prevents the piston from completing its stroke, potentially bending connecting rods or cracking the piston itself. Meanwhile, coolant mixing with the engine oil (creating a milky, frothy substance on the oil cap) severely degrades the oil's ability to lubricate. This leads to increased friction and heat, damaging bearings, camshafts, and other internal components.
The following table outlines the key symptoms and the severe risks they indicate:
| Symptom | What's Happening | Potential Consequence |
|---|
| White, Sweet-Smelling Exhaust | Coolant is leaking into the combustion chamber and being burned. | Damage to the catalytic converter; misfires. |
| Overheating Engine | Coolant loss prevents the engine from dissipating heat properly. | Warped cylinder head/engine block; further cracking. |
| Milky, Frothy Engine Oil | Coolant is mixing with the oil in the crankcase. | Complete engine bearing failure due to lack of lubrication. |
| Loss of Coolant with No Visible Leak | Coolant is burning inside the engine. | Severe overheating and engine seizure. |
| Rough Idle or Misfiring | The crack disrupts compression in the cylinder. | Damage to the catalytic converter and oxygen sensors. |
The only safe action is to stop driving immediately and have the vehicle towed to a qualified mechanic. They will perform a compression test or a leak-down test to confirm the diagnosis. Repair typically involves removing the cylinder head, which is a labor-intensive job, and then deciding if it can be welded or must be replaced. The cost of repair is significant, but it is far less than the cost of a new engine.
