Fluid flow?

yzinger · December 18, 2021

Hey guys, 2021 Sierra Elevation X31. A couple times now I have moved truck after a rain and i hear water pour out at what sounds like front doors area. Before I had a Tonneau i thought perhaps water in bed but now this happens still even though looking in box shows no moisture. Wth is going on? Anyone else experience this?

I had a thought tonight that maybe those hand holds or whatever we call near the tailgate are actually filling with water in a rain and then flowing forward when truck moves??

Thoughts?

txab · December 18, 2021

Maybe it's water trapped in your doors. Check to make sure the drains are open

yzinger · December 18, 2021

didnt know this could be a thing...please explain more and where plugs are?

Supreme Pizza · December 18, 2021

Are you getting water puddles on the ground? If not, then I would guess that its air bubbles being flushed through the heater core. The increase in RPM's when you hit the gas will increase the flow rate and volume of fluid thought the heater core. Any air bubbles will be make noise like water flushing through a rain gutter. New rig, so it might have a little bit of left over air in the cooling system.

yzinger · December 18, 2021

thanks for replies so far. Interesting about heater core.

I do swear once that water poured out of my door but it was all so fast and I wasnt expecting anything that i couldnt be sure as ground was soaked already.

dsr611 · December 18, 2021

1 hour ago, yzinger said:

didnt know this could be a thing...please explain more and where plugs are?

Don't know about the '21 models, but on my '11 3500HD Denali, there is a piece of "weather stripping" along the bottom of the door that just snaps into place. There are holes in the corners that is supposed to allow any water that gets in the doors to drain out; holes are so small, though, that they get plugged up alot and trap water in the doors

Grover67 · December 18, 2021

Check between the front of door where it meets the front fender, might be some sound deading material separating it. Check the bottom area, in the fender, to make sure there is nothing blocking the drain hole. You'll find the sound deading material probably wet too....

-Grover67

Transient · December 18, 2021

Water in doors is very real. Doors are not made to be water tight like on a submarine. Water can get into the doors. If the drain holes are clogged it will prevent the water from draining out.

As for your theory about the hand grab holes/stake pockets in the top sides of the bed, 1) they have drain holes in the middle and are not sealed on the sides either. The water will drain. 2) the bed isn't connected to the cab. Water in the stake pockets cannot travel to the front doors.

Edited December 18, 2021 by Transient

yzinger · December 18, 2021

yup all good points. Thanks.

If there was a consistency to it i could come up with a plan to see if actual water flows out. Maybe it is the heater core suggestion. I will report back forsure when i found out wtf it is.

Thanks again all.

Tahoe02 · December 22, 2021

Mine does the exact same thing and sounds like the drivers side front door, as soon as I drive off it sounds like the water flows from the front to the rear. It only does it during the initial take off. I thought the front fender where it meets the front door may have been the issue, I checked the drain in that spot and it was clear. I will check the door drain.

Supreme Pizza · December 22, 2021

Wait a minute. Couldn't you just have your mother in law sit on the hood and then sit on the rear bumper? That would cause any water to flow forwards and backwards. Might damage the shocks, but it is what it is. Aside from all the rolls of fat jiggling and the eye watering flatulence, you should be able to hear any water flowing thought the body panels. Just ask her wear Depend diapers to absorb the urine, so that the sound of the urine flowing out of her shorts doesn't mess up your testing procedure.

Don't like that idea? Ya, me neither. If you want to eliminate the "air in the heater core" theory, just pop your serpentine belt off for a quick test. You don't even need any tools. Just grab the belt and pull the slack out of it. Then slowly let the belt retract, while moving it to the side, so it walks itself off the pulley. Takes 24 seconds to remove the belt and disable the water pump, last time I checked. Then start and drive the truck. If the noise gone, then its not a cooling system issue - If the noise is still there, then its nothing to do with the heater core. You can run the motor for 60 seconds without the belt attached, without causing any problems or damage.

Edited December 22, 2021 by Supreme Pizza

Transient · December 22, 2021

3 hours ago, Supreme Pizza said:

Wait a minute. Couldn't you just have your mother in law sit on the hood and then sit on the rear bumper? That would cause any water to flow forwards and backwards. Might damage the shocks, but it is what it is. Aside from all the rolls of fat jiggling and the eye watering flatulence, you should be able to hear any water flowing thought the body panels. Just ask her wear Depend diapers to absorb the urine, so that the sound of the urine flowing out of her shorts doesn't mess up your testing procedure.

Don't like that idea? Ya, me neither. If you want to eliminate the "air in the heater core" theory, just pop your serpentine belt of for a quick test. You don't even need any tools. Just grab the belt and pull the slack out of it. Then slowly let the belt retract, while moving it to the side, so it walks itself off the pulley. Takes 24 seconds to remove the belt and disable the water pump, last time I checked. Then start and drive the truck. If the noise gone, then its not a cooling system issue - If the noise is still there, then its nothing to do with the heater core. You can run the motor for 60 seconds without the belt attached, without causing any problems or damage.

Sheet metal is too thin nowadays. MILs sitting on the hood would yield the same result as if you clips the back legs of a cow and had its rear sit on the hood. Those are 2 large butt cheek imprints.

Don't ask me how I know.

yzinger · December 22, 2021

The problem with using the belt to check the heater core for the culprit is that the sound is not consistent - i mean it doesnt happen everytime I drive truck.