Piston Slap: Running on a dead cylinder?

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Brooklynn writes:

Hi, I have a 2002 Chevy Impala 3.4-liter with a bent connecting rod and broken piston. My fiancé and I got into a debate on if the car could still run with only five pistons functioning and one completely removed, or if it would have coolant mixing in with the oil somehow. I don’t think the pistons have anything to do with the coolant and oil mixing, but I would like to know who is right here. I’ve Googled it with no luck so I figured might as well ask somebody!

Sajeev answers:

I’m sure there’s a GM Displacement on Demand joke here, but the short answer is yes: Yank out the busted connecting rod/piston, and the Impala will run. The long answer? It won’t run for long, and the duration depends on several things.

Perhaps this is better to list it out:

  • Coolant mixing with oil: You are correct about coolant, unless the head gasket also blew during the Impala’s “throwing of the rod.” If so, it’s gonna die quickly.
  • Metal shavings: A bent rod implies metal bits fell into the oil pan and will eventually circulate through the system, which will kill the Impala in a matter of miles. But let’s say you got it all out when removing the broken rod, which leads to …
  • Unnecessary fuel: That empty void (where the piston lived) will shoot pressurized fuel into the oil pan, which contaminates the oil. At some point contaminated oil overfills the pan to the point at which it drags against the crankshaft’s rotational motion. Disconnect the fuel injector to keep this from happening.
  • Shake, shake, shake: The resulting imbalance on a 60-degree V-6 (or any engine for that matter) results in even more internal damage that will eventually kill the motor. But, depending on your commute, you might get days or even weeks of use out of it!

No matter—I appreciate your question and I wish your Impala a short and painless end to its life.

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