* Head Gasket Failure: This is a common and serious cause. A blown head gasket allows combustion gases to enter the cooling system. These gases increase pressure, forcing coolant out of the system. The pressure builds while the engine is running hot, and then releases when the engine is turned off and cools slightly.
* Cracked Cylinder Head or Block: Similar to a head gasket failure, a crack in the engine block or cylinder head allows combustion gases or coolant to mix, leading to pressure buildup in the cooling system.
* Faulty Pressure Cap: While less likely to cause *significant* overheating on its own, a faulty pressure cap may not release pressure properly when it's supposed to. This can contribute to the problem, especially in conjunction with other issues. A failing cap might not relieve pressure until the engine cools somewhat after shutdown.
* Radiator Cap Issues: Similar to the pressure cap, a faulty radiator cap can also contribute to pressure buildup.
* Blocked Radiator or Water Pump: Though these would likely cause overheating without necessarily spewing antifreeze *after* shutdown, if the pressure is extreme enough, they could still contribute to the issue. A severely blocked system builds up tremendous pressure.
Important Note: Spewing antifreeze after an overheat is a serious issue. Driving a vehicle with these symptoms risks significant engine damage. Do not attempt to drive the vehicle until the cause is diagnosed and repaired by a qualified mechanic. Continued driving could lead to catastrophic engine failure.
