Audi S4 Engine is making a gurgling sound Inspection at your home or office.

Common reasons for this to happen:

• Inexpert Coolant Service: The most common reason for air to be trapped in your system is that it wasn’t bled out properly when your coolant was changed. There are several ways to bleed air from the coolant system, including using a funnel on the radiator attached to a special tool that allows mechanics to run the engine while filling the coolant. There are also bleeder valves located on the coolant lines (notably at the back of the engine) that let you bleed air out.

• Blown Head Gasket: A blown head gasket can allow exhaust gases to enter the coolant, which becomes trapped in the system and can cause a bubbling or gurgling sound during operation. If this is the case, you may also notice that your engine doesn’t run as well as it used to because it’s losing compression due to the leak.

• Air in the Heater Core: Your car’s heater core uses coolant to provide the heat for your cabin. If air makes it into the heater core, you’ll hear a bubbling or gurgling sound from the passenger side, behind the glovebox.

• Low Coolant: If your coolant is low, then air moves in to fill the void left by the missing coolant. Again, this creates air pockets in your system, which cause the gurgling sound. Low coolant is generally caused by a leak or several leaks, including from cracked hoses, a leaking water pump gasket and many other possible locations.

• Normal Operation: As mentioned above, some vehicles have an expansion tank as part of the coolant system, and hearing some bubbling/gurgling is normal with these types of systems.