Waterfall sound under dash
 

My 2001 Silverado, 4.3L, manual transmission has a waterfall sound under the dash when driving. I suspect air in the cooling system, but don't know how to get it out. When I take the expansion tank cap off, there is no pressure, the truck doesn't overheat and the heater blows good and hot.
I suspect that I also have an intake manifold leak, but have put a bottle of BG cooling system sealer in the system and the leak seems to have stopped.
Any ideas?
Steve 91Sportside

Re: Waterfall sound under dash
 

I have a 2002 Silverado with the 4.3 also. Same thing with the water sound. It seems like I hear it every morning when I start it up and drive away. It stops after a few minutes. I think I have a coolant leak some where. My coolant light comes on every so often.I top it off and the light goes off. Its obvious that the water is going some place.I hope to hear others on the subject.I heard about water pump issues.

Re: Waterfall sound under dash
 

i have the same noise in my 2006 2500HD

Re: Waterfall sound under dash
 

My 99 5.3L does the same thing and the "Low Coolant" light has been coming on the dash as well. I've noticed that when you shut the truck off and turn it back on the light is gone. That's puzzled me.

I'm very anxious for someone to chime in on this one that knows what they're talking about.

Cory

Re: Waterfall sound under dash
 

You have a leak in your heater core.

Re: Waterfall sound under dash
 

Is that something a somewhat mechanically inclined person can change out? Are they very expensive?

Re: Waterfall sound under dash
 

Same thing with my 2000 Silverado 4.8L V8. Turned out to be low on coolant due to water pump leaking. From what I understand this is a pretty common problem with water pumps on this model. The noise is due to coolant being low and when the rpms go up the water pump pushes water into the heater core.

Re: Waterfall sound under dash
 

4.8-6.0s have problems with water pumps leaking
4.3s have problems with thermostats going bad and intake gaskets leaking.

the ONLY way i have found to remove air from the coolant system on the trucks that you have to fill from the overflow tank, is with a special tool called an Airlift