Possible Hydrolock

[Chrisgreenm]

I own a 2006 sierra denali with the 6.0 gas. A few days ago I drove through a pretty deep puddle (I know the danger now) and immediately after my engine started knocking. It never stalled, never died or stumbled while in the water. I pulled my intake and it was full of water, filter was soaked. I let it dry while I worked, and let the filter sit in the sun for a bit. Put it all back together and on startup and at idle it did not knock. I could even raise the rpm's and it wouldn't. However once I got about 60 seconds into my drive it started again. Same thing today, it didn't do it on startup or revving at idle but once I put it in drive and went it came right back. I know the obvious answer everyone's gonna say is I bent a rod when I hydrolocked a cylinder, but wouldn't that make noise consistently? And raise with rpm's? Looking for if anyone knows any other possible reason as to why it's knocking or what I'm missing here

[richard wysong]

How's the oil look?

[Grumpy Bear]

Electricity and water are never a good mix. It isn't hydro-locked. And yea, what Richard said. 

[richard wysong]

Try it without the air filter and see if that helps. The water may have damaged it

[Chrisgreenm]

16 hours ago, richard wysong said:

How's the oil look?

Oil is clean. Changed it a little bit before the incident and it's still clear clean looking oil, not milky.

[Silverado4x4]

With the airbox soaked with water the water may have damaged the MAF sensor and screwing up the air/fuel mixture.  You don't have any codes? I would try and disconnect the battery for about 15min or longer to reset the computer as this could have screwed up the readings for the computer. Yeah definitely not hydrolocked. 

Edited June 13 by Silverado4x4

[Grumpy Bear]

15 hours ago, Silverado4x4 said:

With the airbox soaked with water the water may have damaged the MAF sensor and screwing up the air/fuel mixture.  You don't have any codes? I would try and disconnect the battery for about 15min or longer to reset the computer as this could have screwed up the readings for the computer. Yeah definitely not hydrolocked. 

 

Good thought! 

[PunchT37]

Is all the water out of the intake? Some are almost impossible to get all the water out. It will sit in there till revved. Then, boom.

[Chrisgreenm]

On 6/13/2025 at 5:53 PM, Silverado4x4 said:

With the airbox soaked with water the water may have damaged the MAF sensor and screwing up the air/fuel mixture.  You don't have any codes? I would try and disconnect the battery for about 15min or longer to reset the computer as this could have screwed up the readings for the computer. Yeah definitely not hydrolocked. 

I do have codes like p300 and lean fuel on bank 1 but I had that before. No new codes. I pulled the tube off from the box to the throttle, should I pull the throttle and intake manifold too? Maybe waters stuck in the manifold and causing noise?

[Chrisgreenm]

On 6/13/2025 at 10:14 AM, richard wysong said:

Try it without the air filter and see if that helps. The water may have damaged it

Without the filter it makes the same noise

[Chrisgreenm]

On 6/14/2025 at 8:55 PM, PunchT37 said:

Is all the water out of the intake? Some are almost impossible to get all the water out. It will sit in there till revved. Then, boom.

Up until the throttle yes, I didn't go further than that. Would it get past the throttle and stay there?

[PunchT37]

40 minutes ago, Chrisgreenm said:

Up until the throttle yes, I didn't go further than that. Would it get past the throttle and stay there?

On many modern engines, once a liquid gets in the intake, it`s a good idea to change it. You can`t just pour it out. It will stay in the bottom of the long runners. Then, with enough air velocity, it will make it to the cylinder. Then, a bent or thrown rod. Maybe not your particular intake but, something to think about. I would at least pull it and see if water is in it, and if you can get it all out.

[Chrisgreenm]

On 6/16/2025 at 9:17 AM, PunchT37 said:

On many modern engines, once a liquid gets in the intake, it`s a good idea to change it. You can`t just pour it out. It will stay in the bottom of the long runners. Then, with enough air velocity, it will make it to the cylinder. Then, a bent or thrown rod. Maybe not your particular intake but, something to think about. I would at least pull it and see if water is in it, and if you can get it all out.

So I finally got around to pulling the manifold. There was a decent bit of water in there mixed with oil. Got it all out and dried it, reinstalled and the noise is still there. 

[Chrisgreenm]

Anyone have any ideas what could be rattling around? I've checked it over and over and I don't see anything. Maybe it warped something like my exhaust? Did hit the puddle right after coming off the highway so it was definitely hot

[PunchT37]

If it`s not the engine, then maybe the cat core is broken and rattling around. The cat is usually very hot and driving through cold water shocks the ****** out of it.