Been hearing it a lot lately, it is something new. Any idea what this mystery noise is?

 

Low on coolant for sure.

 

mine does the same thing occasionally if I am sitting in it and it is ideling while fully warmed up. I probly just need to remove the reservoir cap and try to get more air out of the system. I have no negative cooling issues

 

Low coolant light isn't on, truck runs cool. I'll check the level again tomorrow. Funny thing is, this started once the weather got colder. I bought the truck in July, the noise started about a week ago.

 

It low coolant. Put the cap and check it. Let it warm up and check it. You will see my friend.

 

Mine did that when I would be using defrost on cold mornings. Ever since I had my coolant flushed it stopped.

 

You are hearing air bubble in the coolant rushing in the heater core. If you rev the engine in neutral you will hear it too.

 

I swore up and down I had the same issue... Turned out it was my gauges making the noise. Very weird. Mine was faint though.

 

Same here. I just here it at idle and when I rev it it kinda goes away. My defog and heaters rent wrking.. Wonder what it is. As soon as the weather gets better I'll dig under the hood

 

Mine did this too, it was just because of low coolant. It would happen even when the low coolant light wasnt on.