Why Is My Car Making Gurgling Noises?by Richard Rowe
Engines are a lot like the human body, which is a pretty noisy thing if you listen closely enough. A gurgling sound coming from under the hood could indicate a lot of things from the mundane to the very serious. Odds are good though that it's nothing to lose sleep over or a simple fix.
Generally speaking, gurgling noises are the sound of air or water moving around in your cooling system. This tends to happen most when the engine is very hot, and is very common after shutting a hot engine down. In this case, the sound you're hearing may just be water and steam moving to and from the coolant overflow bottle, or through the cooling passages. Gurgling noises are often associated with overheating for this reason, but you'll know if that's the case according to your temperature gauge. If the problem is persistent, try bleeding the air out of your cooling system, since trapped air bubbles are a major cause of both overheating and gurgling. It's common to hear gurgling under the dash if there's air in the system -- coming from the heater core.
In terms of severity, the problem could be on either side of that. Some engines are just known to burble, and the noise gets more pronounced when you install something like a short-ram or cold-air intake. If this is the case, it's nothing to be concerned with. Of slightly more concern are serious potential failures, like blown head gaskets and cracked engine blocks. Odds are good that these will exhibit other significant symptoms, though. Check the coolant with the radiator cap open; if you see oil floating on top, or smell gasoline with the engine running, you may have a serious problem in the bowels of the beast.