Could driving my truck through a puddle be enough to hydro-lock an engine?

Dear Car Talk

Dear Car Talk | Aug 01, 1999

Dear Tom and Ray:

My '94 Toyota truck drowned going through a BIG puddle. When I first tried to
restart it, the starter grunted and gave up. So I waited for everything to dry
out. Unfortunately, it still does the same thing. Jump-starting doesn't help, and
when I tried to push start it, the tires squealed because the engine was
completely frozen up. Am I in deep doo-doo? Is it bad starter doo-doo or new
engine doo-doo? The truck has given me no trouble until now. -- Chris

TOM: Oh, you poor guy, Chris. I think you're deep in new engine doo-doo.

RAY: Here's what probably happened. When you went through that "big puddle,"
water got sucked up into the engine's air intake.

TOM: The air intake normally draws air into the cylinders. But in your case, it
drew water in. And once one or more of your cylinders had water in it, the engine
became "hydro-locked."

RAY: The way the engine usually works is that the pistons suck in air and
compress that air. But water can't be compressed like air, so when the cylinders
are full of water, the engine just stops.

TOM: At this point, there are two possibilities. One is that no significant
damage was done to the head gasket, valves, pistons or connecting rods, and once
you blow out the water, the engine will run fine again (you do this by removing
the spark plugs, cranking it and watching Old Faithful shoot out of your spark
plug holes). This is also known as the "you should BE so lucky" possibility.

RAY: The other, much more likely possibility is that you've already ruined the
engine -- if not in the puddle itself, then by trying to jump-start and roll
start it. And in that case, you're in for an engine rebuild. We wish you the
best, Chris. And stay out of those big puddles in the future ... especially the
ones that show up on maps.

Get the Car Talk Newsletter

Got a question about your car?

Ask Someone Who Owns One