Waterfall sound in dash at startup

[tjonesdfw]

Recently, at startup on a 2021 Sierra 1500 with the 5.3, I’m hearing a loud waterfall/rush of water sound in the passenger side dash. I’m assuming it’s air pockets in the heater core, but it’s unusually loud.  The cooling overflow tank is low… about half way between the full line and the bottom of the tank.  There’s a sludge line or darker dried line of coolant slightly above the fill line where it appeared to have been at one time, and it was at the fill line a year ago. No visible leaks anywhere or any coolant on the ground at the moment.  Can these trucks eat that much coolant or do I need to ask the dealer to pressure test the cooling system?  Are there any common leak spots to look for? 

[Bikerjon]

37 minutes ago, tjonesdfw said:

Recently, at startup on a 2021 Sierra 1500 with the 5.3, I’m hearing a loud waterfall/rush of water sound in the passenger side dash. I’m assuming it’s air pockets in the heater core, but it’s unusually loud.  The cooling overflow tank is low… about half way between the full line and the bottom of the tank.  There’s a sludge line or darker dried line of coolant slightly above the fill line where it appeared to have been at one time, and it was at the fill line a year ago. No visible leaks anywhere or any coolant on the ground at the moment.  Can these trucks eat that much coolant or do I need to ask the dealer to pressure test the cooling system?  Are there any common leak spots to look for? 

Oh yes engines can leak coolant internally. I would get the coolant system pressure checked and have them check for "milky" engine oil.

[Gangly]

10 hours ago, tjonesdfw said:

Recently, at startup on a 2021 Sierra 1500 with the 5.3, I’m hearing a loud waterfall/rush of water sound in the passenger side dash. I’m assuming it’s air pockets in the heater core, but it’s unusually loud.  The cooling overflow tank is low… about half way between the full line and the bottom of the tank.  There’s a sludge line or darker dried line of coolant slightly above the fill line where it appeared to have been at one time, and it was at the fill line a year ago. No visible leaks anywhere or any coolant on the ground at the moment.  Can these trucks eat that much coolant or do I need to ask the dealer to pressure test the cooling system?  Are there any common leak spots to look for? 

This is a very common issue, don't worry.  Fill the coolant reservoir about an inch above the coolant level indicator, place the truck on an incline, and let it run for about 10 minutes. Air somehow gets in the system over time and coolant gets "lost".

 

My truck had this issue from Day 1.  I finally took it into the dealership, they flushed the system, and it the waterfall noise went away for a long time.  The issue popped up again later on, and I read about the quick fix remedy of overfilling and running the vehicle on an incline, so I gave it a try.  Sure enough, the waterfall/gurgling went away and I haven't had issues with it since. 

 

Good Luck!

 

 

[tjonesdfw]

3 minutes ago, Gangly said:

This is a very common issue, don't worry.  Fill the coolant reservoir about an inch above the coolant level indicator, place the truck on an incline, and let it run for about 10 minutes. Air somehow gets in the system over time and coolant gets "lost".

 

My truck had this issue from Day 1.  I finally took it into the dealership, they flushed the system, and it the waterfall noise went away for a long time.  The issue popped up again later on, and I read about the quick fix remedy of overfilling and running the vehicle on an incline, so I gave it a try.  Sure enough, the waterfall/gurgling went away and I haven't had issues with it since. 

 

Good Luck!

 

 

After overfilling did you run it with the cap on and sealed, or with the cap off to burp air out of the system?  I understand and have had air pockets in a cooling system before, but not sure how that correlates with the coolant level dropping without there being a leak somewhere.    

[Gangly]

Leave the cap on.  

 

I don't know where the coolant goes.  I change the oil myself, and I have never observed coolant in the oil.  I have also drained the coolant myself and didn't notice anything in the coolant either.  I have 130K+ miles on the truck and have never noticed anything other than a coolant loss when diagnosing the startup sound. 

 

I have noticed overtime, that once the truck starts gurgling on startup, or waterfalling, the coolant is low.

Edited September 5, 2024 by Gangly

[Silverado4x4]

I did basically the same thing as Gangly on my 2019 but I just got the motor warm and squeezed the top radiator several times and I could see the bubbles coming out in the reservoir, after filling up the reservoir a few times to the level the gurgling stopped. 

[BlancoSilverado]

I had the same problem, pulled a vacuum on the cooling system and watched the air burp in the bottle. 

 

** I do not remember if I was able to pull a full vacuum. i believe it was roughly half. **

Edited September 5, 2024 by BlancoSilverado
**additional info**

[cfell]

What condition is truck?  Mileage? It is possible you have a bad head gasket?  Yes.  
 

more likely, in really hot weather the h2O boils off… 

 

Also, if new, hoses can expand a bit under pressure.. 

 

if this is a 6.6 diesel, the reservoir/coolant overflow is waaaay different and you don’t want to vent unless you are sure of the procedure.

[tjonesdfw]

7 hours ago, cfell said:

What condition is truck?  Mileage? It is possible you have a bad head gasket?  Yes.  
 

more likely, in really hot weather the h2O boils off… 

 

Also, if new, hoses can expand a bit under pressure.. 

 

if this is a 6.6 diesel, the reservoir/coolant overflow is waaaay different and you don’t want to vent unless you are sure of the procedure.

45k miles, well maintained, so was surprised to see it so low absent a leak.  

[PunchT37]

On 9/5/2024 at 8:50 AM, tjonesdfw said:

After overfilling did you run it with the cap on and sealed, or with the cap off to burp air out of the system?  I understand and have had air pockets in a cooling system before, but not sure how that correlates with the coolant level dropping without there being a leak somewhere.    

The coolant level can drop as it takes up the empty spaces the air was in. It should keep a level once purged.

[tjonesdfw]

Finally got the truck back to the dealer and they say the cooling system failed the pressure test, yet they can't locate where the leak is yet.  The saga continues... 

[tjonesdfw]

The cooling system failed a pressure test yesterday indicating a leak, then dealer claims it passed a pressure test today.  They pulled a vacuum on it, filled it up, and said come get it.  Wonder how long it takes to drop again.  

[Bikerjon]

10 hours ago, tjonesdfw said:

The cooling system failed a pressure test yesterday indicating a leak, then dealer claims it passed a pressure test today.  They pulled a vacuum on it, filled it up, and said come get it.  Wonder how long it takes to drop again.  

Dude again, you need to find yourself another dealer.

[tjonesdfw]

7 hours ago, Bikerjon said:

Dude again, you need to find yourself another dealer.

Had to use this dealer due to an ongoing GM customer service situation but I definitely won’t be going back anymore!

[tjonesdfw]

Back to another dealer next week with the same issue again... waterfall sound at startup, about an inch low in the tank, and the smell of coolant around the front of the truck every time I stop. Hoping this new dealer properly diagnoses, because in my mind there has to be a small leak somewhere.