I hear sound of water sloshing the first couple of times I accelerate and stop in the morning. Like a very small wave coming in to shore. Sounds like it coming from under the glove compartment. The sound goes away after those couple of times it happens in the morning. Haven’t noticed any water coming into the cabin or on the floor mats. No other issues with the vehicle 2017 Colorado. Any ideas?
There’s probably air trapped in the cooling system.
And what you’re hearing is the coolant running thru the heater core.
Tester
Yep…what @Tester said. Unless its all the water in the pickup truck bed you have, rolling out and drenching the parking spot you just pulled out of because it rained the night before? lol
Ha! Nope, no puddles left behind me 
Thx!
Thanks so much! Is this something to be concerned about? In other words, could it be harmful to the vehicle? I’m guessing I would just need to have somebody bleed the air out of the cooling system?
Yes it can be harmful… You need to check your coolant level and be sure it is full… It should purge the air out itself within a few hot and cold cycles of the engine.
Reservoir is full? No cap on radiator to check in there.
Tried to upload picture but the reservoir is topped off so I don’t see how it could be lack of coolant
Looking around and I’m starting to think that it might be a clogged AC drain hose. Anyone have any idea where that is located on a 2017 Colorado? It seems to typically be located somewhere in the firewall area.
It is… usually passenger side… firewall area. Look for a rubber tube on the pass side near firewall. Make sure the tube is clear of obstructions… Oh and dont look directly up the tube when poking wire up thru it… ask me how I know.
Well if there is a drain line on this thing, I sure as heck can’t see it or find it. But what I did find is that the AC seems to be draining out of a pre-cut hole in the firewall. You can see a drop of water in the picture. Does that seem like normal design?
Ummm… NO it does not
So my guess then is that the AC drain hose (wherever it is) is clogged and the AC condensation is overflowing and somehow getting behind the firewall and then coming out of this hole? Agree/disagree? Thanks!
The A/C resides basically passenger side… at the firewall… behind the glove box. Look under your dash on the pass side… you should see a black box intruding into the pass side…going toward the driver side.
Thats the A/C evaporator and heater core…that box needs to drain…
Use the internet to search about it… it is your friend.