Is "hydro-lock" code for "this engine is sunk"?

Dear Car Talk

Dear Car Talk | Apr 01, 2004

Dear Tom and Ray:

My 18-year-old daughter drove her 1995 Dodge Neon Sport to high school Monday, which happened to coincide with a record rainfall here. The parking lot at her school was a lake. She drove into it, and her car died. After the rain stopped and the water receded, we tried starting it, to no avail. We had it towed. There was oily stuff underneath, and the tow-truck driver said it looked like the block was cracked. Can driving a car into a very deep puddle cause the block to crack? The school principal says he doubts it, but my mechanic son says the principal needs to go back to school on this one. He says driving a hot car into a cold lake will cause that engine to pop. Who is correct? Also, who do you think is responsible for such an event -- the school or Dodge? -- Les

TOM: Who's responsible? I would say it's some combination of your daughter and God. One created the puddle, and the other drove into it.

RAY: My guess is that the car hydro-locked. There are three elements required for combustion inside the cylinders: air, fuel and spark.

TOM: You'll notice that water is not one of the elements, Les.

RAY: If you drive through a deep enough puddle, water can get sucked up through the air intake and get inside the cylinders. And unlike air, water cannot be compressed by the pistons. So when the pistons hit the water, the connecting rods and crankshaft get mashed and bent. Sometimes, one of the rods will even pierce through the side of the engine block. And boy, is that exciting!

TOM: It's possible to have an engine block crack in cold water, but it's very unlikely. We've never seen it happen. So, I think the hydro-lock theory is much more realistic. Either way, this engine is sunk, Les.

RAY: You should check with your insurance company, in case it'll put more of the blame on God than on your daughter. But if not, your daughter just learned an expensive lesson about driving through water, Les.

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