Hydrolock

Hydrolock, also known as hydraulic lock or hydro-lock, is a phenomenon that occurs when a non-compressible fluid, such as water or oil, enters a combustion engine's cylinder where it cannot be compressed by the piston. This typically happens when a vehicle drives through deep water or if there's a breach in the engine's intake system allowing liquid to enter. The piston attempts to compress the fluid along with any air present. However, since liquids are virtually incompressible, this creates immense pressure within the cylinder. This extreme pressure can cause significant damage to internal engine components.

The consequences of hydrolock can be severe. The connecting rod, which connects the piston to the crankshaft, is often the first component to fail, bending or breaking under the immense force. The piston itself can be damaged, and in extreme cases, the cylinder head can be cracked or warped. The crankshaft can also be affected. The engine will cease to run immediately and will not restart.

Preventing hydrolock involves avoiding driving through deep water, especially if the depth is unknown. If a vehicle does drive through water, it's advisable to drive slowly and at a higher RPM to minimize the chance of water being sucked into the intake. If hydrolock is suspected, the engine should not be cranked again. The vehicle should be towed to a mechanic for inspection and repair, which will likely involve draining the cylinders and inspecting for internal damage.