How to Use a Radiator Pressure Tester

by Jody L. Campbell

The radiator and cooling system on a vehicle are responsible for cooling the internal components of the combustible engine. To operate, the engine encounters several small controlled explosions in the cylinders per second. Combined with internally moving parts, friction also applies heat. To cool the engine, the radiator and cooling system work under pressure in a sealed environment. Boiling temperature of the system is increased due to the sealed pressure. If a leak occurs, internally or externally, or if pressure is lost, the boiling temperature decreases and the engine will overheat.

Step 1

Ensure the engine is cold before attempting to check the pressure on the radiator. Slowly remove the radiator cap by pushing down and then turning it counterclockwise until the locking tabs on the cap release. Some caps my offer a flip-top pressure release valve on top of the cap. If so, lift the pressure release valve upward to release the pressure inside.

Step 2

Look on the top of the radiator cap to discover what the exact psi pressure rating is for the vehicle.

Step 3

Make sure the radiator and coolant reservoir bottle are full of coolant to the maximum fill line. Radiators should be filled to just below the top of the cap and reservoir bottles will have a full-cold indicator line. Some vehicles use the reservoir as the pressurized chamber to run directly to the radiator.

Step 4

Apply the attached radiator cap extension of the pressure tester to the radiator. Different makes and models of cars may come with different sized radiator necks and caps. Most pressure testers come with a couple adapters of the most common ones used, but in some cases with imports, a special adapter might have to be employed. The adapters screw onto the radiator neck and then the top of the adapter fits the standard radiator cap extension of the pressure tester. Make sure if an adapter is employed, it is screwed onto the neck of the radiator properly and tightened. Make sure the radiator cap extension of the pressure tester is screwed on securely and tight.

Step 5

Pump the cylinder handle of the radiator pressure tester while watching the psi gauge. Do not exceed the psi pressure listed on the radiator cap. Internal seals or weak hoses can burst if too much pressure is applied. Once the desired pressure is obtained, gently rest the pressure tester on the frame rail or radiator rail. Visually inspect all around the radiator and around the bottom of the engine area under the vehicle for any visible signs of dripping or leaking. This tester under pressure will reveal any small leaks and help you identify the failed component. Heater cores, part of the cooling system, are internal between the firewall and floorboard on the passenger side of the car. You won't be able to see the hoses or the core leak under a pressure test, but you'll be able to smell coolant inside the passenger cab of the vehicle.

Step 6

Allow a few minutes to go by and check the psi gauge on the pressure tester. If no leaks are apparent and the tester has maintained the applied pressure, the system is okay. However, if the pressure is less than a couple notches away from the applied pressure setting, there may be an internal problem with the head gasket or heater core.

Step 7

Release the pressure on the pressure tester before removing the cap. Again, pressure is now built up inside since you manually purged it in. Removing the cap of the tester before releasing the pressure will result in coolant spraying everywhere. Some testers have a pressure release rod or valve. Other cheaper models may simply employ manually and gently tipping the cap on the radiator neck to release the pressure slowly. When the psi gauge reads zero pressure, you can safely remove the cap and/or adapter, if applicable. Replace the radiator cap.

More Articles

article divider