Loud knocking, water got into air intake


Please help! I was stuck in a bad rain storm yesterday through about 1.5 feet of water and the car stalled. I was able to restarted it and drove home about 1 mile away. By the time I got home, the engine starts to knock very loud. The air filter was totally wet and it appeared that some water got into the air intake. I towed the car to a mechanic and is waiting to be checked. The knocking improves about 30% and the car can now start and run OK … but the knocking remains. Please give me some advices. Thank you very much in advance.


I think you are out of luck with major engine damage. That is called hydraulic lock. Air in an engine compresses which is normal, but water in the cylinders will not compress so the pistons come up, hit the water, and stop in their tracks. The result is bent piston rods, broken pistons, bent crankshaft, etc. from the force. I wouldn’t spend much money on a diagnosis but instead put it into a new short block or long block would be better with the heads already on it.


I was thinking if it really hydrolocked the engine or not … the car can still start and run OK except for the loud knocking sound. Thanks.


I fear Bing is right. It does not take much water to do a lot of damage. It is not wise to try and go through standing water. You may do it a dozen times without a problem and then…


This has come up a few times on this board in the last couple of weeks. ?I drove through a deep puddle of water, my car died, I was able to get it to start but now it knocks?. The diagnosis is always the same ?You hydro-locked your motor and now it is thrashed?. Explanations of bent rods and valves accompany this tale of disaster.

I have a slightly different take on these events. While I have the utmost respect for the majority of the posters on this board I think they are off base on this one. I have seen head gasket and cylinder head failures that allowed massive amounts of water enter a cylinder. They have even been posted on here before. ?My car is spewing clouds of white smoke what could be the problem?? This tells me that water entering the combustion cylinder doesn?t necessarily cause catastrophic engine failure.

This is not to say that it cannot happen but I think it is highly unlikely. If enough water entered the system to hydro-lock the motor the starter would not be strong enough to turn the motor over with the water in the cylinder. In Order to get the motor to turn over again the plugs would need to be removed so the water could be pumped out. Since the posters are able to get the vehicle restarted it is my belief that enough water entered the combustion chamber to dilute the fuel air mixture enough to kill the motor but that is it.

Now, what causes the knock? The engine has ingested water into the system. Water made its way through the intake into the cylinder and killed the motor. The first thing the posters do is try to start the car. The starter turns the motor over (slowly I?m sure) continuing to draw the residual water through the intake while expelling the water in the cylinder. Eventually enough water is removed and the engine fires and runs. Even though the engine runs fine after a minute it knocks. It is my belief that the knock is coming from either the starter or the flywheel.

The stress of turning over an engine with water in it is highly capable of bending the starter bendix, breaking teeth on the flywheel, or the flywheel itself. All of which could cause the knocking indicated.

My advice before condemning the engine is to verify the integrity of those components. Thanks for listening to my rant; I will go put my soap box away now. If there are flaws in my thinking please let me know and good luck to the OP.