Strange sound behind dash

So yesterday I had the spark plugs, coolant, and oil changed in my 07 Tacoma. They also cleaned the MAF sensor. I noticed this morning and this evening a sound that almost sounds like water running through pvc pipes. Sounds like it's coming from behind the dash. I've looked in the engine bay and don't see any leaks. Any ideas on what this noise could be?

 

Sounds like maybe the coolant system wasn't burped completely. Still has air in it and you're hearing the bubbles running through the heater core.

With the engine and coolant cold, take the radiator cap off (DO NOT DO THIS IF IT'S HOT). Start the motor and let it run. It needs to get to operating temperature so the thermostat opens and lets the coolant circulate. The air will make its way out the opening. If enough air comes out, you may need to put more coolant in the system.

 

Something I should be concerned with or will it work itself out?

 

No, it needs burped. It's something that should be taken care of.

 

Is there an easy way to do this?

 

It's easy. Just follow the instructions I posted above. I posted them just a few seconds ago. If anythings not clear, just ask.

 

Got ya. Didn't see that. How long do you think it will have to run for all the air to get out? Am I just watching for bubbles?

 

And if that isn't the cause of your sound and the fluid is fine, doing this won't hurt anything. It will just assure you the fluid is good.

 

Let it run for a good 20 minutes. You may see some bubbles pop up, but you'll see the fluid start to go down if the air is working itself out.

 

Did a garage perform the service? If so, you could have them correct it. Its something they should have done anyway.

If you end up doing it, just remember not to open the radiator cap if it's hot. The system is under peessure when hot and will spray hot fluid all over you and cause serious injury.

You may already know all this, I just want to make sure you're informed.