2002 Silverado 4.3 air in coolant system

[GerGa]

Hi guys I have a 2002 Silverado with 4.3l engine. There has been a chugging sound behind the dash for quite a while, like bubbles in water.

Is this just air in the coolant system? Is there some way to bleed it or something else?

 

Thanks

[ifixedit]

I've got a 98 Yukon that was doing the exact same thing. When the system is low on coolant you will hear this sound coming from the dash area, more so when you first start it with the heat set on high when the water pump is just beginning to push the coolant through the system. If it is what I think it is, what you describe hearing is indeed the coolant (or some lack therof) mixed with air sloshing around in the heater core and the heater core lines because the system is low. I'd start out by just adding a 50 / 50 mix of antifreeze and see if that cures it of the noise, it should. If it does you should be fine, but the next question would be is where has the coolant gone that was once there? Could be signs of head or more likely intake gaskets in the early stages of failing. Typically this starts to happen around 120 to 150K miles and gets worse from there. How many miles do you have on it? Does it still have the original DexCool (red) coolant in it? The original intake gaskets of these year vehicles are notorious for getting eaten up, becoming brittle and failing because of material compatability issues with the DexCool over time. This happened to me on my Yukon. When I changed the intake gaskets, the old ones literally came out in pieces and crumbled in my hands and coolant had leaked past them and into the crank case. If this is what's going on and the coolant continues to mysteriously disapprear over time, you want to catch this problem before the intake gaskets completely fail and the entire contents of the cooling system is puked into the crankcase and you have a milkshake. Not good.