Earlier this summer I noticed a bubbling noise from behind the dash and didn't think much about it. But it has slowly gotten worse until today where I investigated it further. The bubbling noise is somewhere on the passenger side under the dash board, not under the hood. The bubbling is silent at idle but gets louder once the revs get past idle. I'm not too familiar with this truck. Is there some sort of coolant tank under there, for the heater maybe? I have noticed my low coolant light coming on. Perhaps there is a connection? I just haven't gotten around to topping off the coolant.

Thanks all!

 

Coolant flows through the heater core. Sounds like air in the line. Just fill the radiator back up and bleed the air out of the system

 

How does one go about bleeding the air out?

 

Fill the radiator up while it's idling and squeeze any air out of the hoses that you can. Someone else can chime in on tips. I think parking on an incline helps but not sure

 

Have you used your heater lately? Sometimes air gets trapped in the heater core if you don't use the heater for a while and it will gurgle when you drive.
Try this first.
Top off the surge tank about an inch over the full line. Go drive around and get the truck hot. Turn the heater on full blast and drive around some more doing stops, starts, left & right turns, etc. Check the coolant level and add more if necessary.

If that doesn't work, do this.

Park the vehicle on a level surface.
Fill the system through the surge tank opening.
Pre-mix a 50 to 60 percent solution of DEX-COOL® and clean, drinkable water.
Slowly add the pre-mixed solution to the surge tank until the level is slightly above the surge tank split line.
Start the engine.
Idle the engine for 1 minute.
Loosely install the surge tank cap. Do not allow the system to build up pressure.
Cycle the engine from idle to 3000 RPM in 30 second intervals until the engine coolant reaches 99°C (210°F) and the thermostat opens.
Shut off the engine.
Start the engine.
Idle the engine for 1 minute. Fill the surge tank to 1/2 inch above the COLD FULL mark on the surge tank.
Install the radiator surge tank cap.
Cycle the RPM. Idle the engine to 3000 in 30 second intervals until the engine coolant reaches 99°C (210°F).
Shut off the engine.
Top off the coolant, as necessary, to 1/2 inch above FULL COLD mark on the surge tank.

 

I added coolant to a little bit past the cold fill line and drove it around with the heater blasting and the bubbling noise is gone!

Thanks for the input.

 

Keep an eye on the coolant level...if it keeps dropping for no apparent reason your water pump probably has a slow leak.

 

The water pump gaskets have been known to fail and leave little to no sign of their leakage also...

 

Agreed. Mine was leaking so I put some RTV on it when we changed the cam