Danger of Air Bubbles in Truck Cooling System

Dangers of Air Bubbles in Your Cooling System


If you have an air pocket or “bubble” trapped within your cooling system, the coolant will not be able to reach and cool that section. You may exceed safe operating temperatures and cause a blown head gasket, warped head, damaged valves or pistons, a cracked engine block, a blown radiator or bursting hoses.

Your truck needs to maintain a tight range of temperatures to run properly. The thermostat quickly brings your coolant temperature up to about 195° degrees to warm the engine and give you heat in the cab. Once the fluid reaches this point, the thermostat will open to allow the radiator to start cooling the fluid to keep it below the boiling point of about 223° for a 50/50 mix. This will give you an operating range of about 30° for the proper cooling of your truck. While your vehicle can run outside of this range for a short time, this is the range you are trying to maintain.

How Does an Air Pocket Develop?

Any opening of the cooling system can cause an air pocket. Flushing the system, a new radiator, changing the thermostat, replacing a hose, a new water pump or any leak can lead to air entering your system. If your cooling system is opened, you must make sure it is filled correctly, and all air is removed. Please note that just taking the cap off and checking coolant levels will not create an air pocket. Also, never open a hot cooling system, let it cool down first.

Cooling System Air Pocket Symptoms

There are a few things that can point to a potential air pocket. You may overheat and see a rise in temperature or uncommon fluctuations in your gauge. You may no longer be getting any heat in your cab. A thermostat or other problem could cause these same signs so have your vehicle checked as soon as possible. All these signs can escalate into a bigger problem unless addressed promptly.

Preventing Cooling System Air Pockets

The best thing you can do to protect yourself from an air pocket is to watch the gauge and double-check your coolant level after any work on your cooling system. Most air pockets will show themselves quickly. It’s key that you watch the gauge and check your fluid right after any opening of the system or changing any cooling system component.

At our shop, we would always run a vehicle after any cooling system work and “burp” the system of air. We would allow the thermostat to open and circulate the fluid throughout the system making sure the heater was working properly. We would then check and double-check all fluid levels, open any bleeder valves and make sure everything was topped off.

Remember, vehicles will not purge themselves and must be “burped”. To “burp” a cooling system the thermostat must be open and the system must be hot and fluid pumping through it. Your heater must be working. All bleeder valves must be opened to release air from any high point in the cooling system. Does your vehicle have bleeder valves? If so you MUST bleed the system.

How to Bleed Air Out of a Cooling System: