Water sloshing at start up

Sly · May 31, 2023

I have a 2020 5.3L and I hear water sloshing around from what sound like the engine compartment when I do a cold start in the morning. So I'm wondering if anyone else hears this same sound?

clstark7 · Jun 1, 2023

I have not had this issue. Maybe try seeing if there are any fluids in your air filter housing. I believe they are set up to drain out, but I am not certain on that. It could reveal a critter that you are actually hearing lol. Does the antifreeze level in the overflow box appear to be at the appropriate level? That should be located at the driver's side by the firewall. I wonder if that could make the noise you are describing as it sucks back into the radiator, if it is low.

mrcolieman · Jun 1, 2023

When stopped or while moving? I get a sloshing sound while moving slowly over bumps from the windshield washer reservoir when it's anywhere below 1/2... I keep it topped up and no sloshing.

Vegas17 · Jun 1, 2023

I have heard it as well. Sounds like its near passenger side from inside the cab. To me it sounds like fluid just being pushed around at startup. Never noticed any issues.

Sly · Jun 1, 2023

clstark7 said:
I have not had this issue. Maybe try seeing if there are any fluids in your air filter housing. I believe they are set up to drain out, but I am not certain on that. It could reveal a critter that you are actually hearing lol. Does the antifreeze level in the overflow box appear to be at the appropriate level? That should be located at the driver's side by the firewall. I wonder if that could make the noise you are describing as it sucks back into the radiator, if it is low.

Thanks, the antifreeze tank is low so I'll top it off and see if that makes a difference. I just did a cold air intake install this last weekend so no water in air box and no critters either lol.

Sly · Jun 1, 2023

mrcolieman said:
When stopped or while moving? I get a sloshing sound while moving slowly over bumps from the windshield washer reservoir when it's anywhere below 1/2... I keep it topped up and no sloshing.

When doing a cold start typically in the morning when going to work and then leaving work after the truck as been parked for about 6-8 hrs. I just topped off the windshield reservoir so I don't think it's that.

Gangly · Jun 1, 2023

Sly said:
I have a 2020 5.3L and I hear water sloshing around from what sound like the engine compartment when I do a cold start in the morning. So I'm wondering if anyone else hears this same sound?

I had this exact issue, as have a few other people. It would only make a sloshing sound immediately on startup and sounds like its coming from behind the dash. It would generally only do it on a cold start and would last for a brief second. I lost maaaaaaybe half a tank of coolant over an approximately 50K miles so I took it to the dealership and they did a pressurized flush of some sort and it corrected the issue. Something about air in the system. Its now been almost 40K miles since then and I am starting to hear it on occasion, but very lightly. If it gets bad enough, I'll just have it flushed again.

Good luck.

Keller · Jun 1, 2023

Mine does this every morning.

That21TrailBossguy · Jun 2, 2023

Gangly said:
I had this exact issue, as have a few other people. It would only make a sloshing sound immediately on startup and sounds like its coming from behind the dash. It would generally only do it on a cold start and would last for a brief second. I lost maaaaaaybe half a tank of coolant over an approximately 50K miles so I took it to the dealership and they did a pressurized flush of some sort and it corrected the issue. Something about air in the system. Its now been almost 40K miles since then and I am starting to hear it on occasion, but very lightly. If it gets bad enough, I'll just have it flushed again.

Good luck.

I knew I wasn’t crazy!! That would drive me nuts and I couldn’t find the source. My 21 now has 20k on it, and during the first few k I heard that noise. Turns out my coolant was low. Had the dealership replace coolant, add dye and pressure test and noise went away as did coolant loss. Dealer chalked it up to not being full of coolant when I took delivery

I didn’t buy that tho. Could be poor bleeding and filling of the system originally

No issues since then.