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Performing a radiator pressure test

Peter Sitkowski | 19th Jan 2024 | 5 minutes to read

Performing a radiator pressure test is a valuable diagnostic procedure to identify potential cooling system issues in a vehicle.

This is actually a fairly simple test to perform, and only requires a pressure tester kit, some safety equipment like goggles and gloves, and a towel for clean-ups. You'll likely also want some coolant that’s compatible with your vehicle and your vehicle's manual nearby for reference.

Below is a breakdown of the steps you'll want to take to check your radiator pressure, as well as tips for clean-up and general maintenance:

  1. Preparing the Vehicle
  2. Identifying the Radiator Pressure Cap
  3. Attaching the Pressure Tester
  4. Inspections After Pressure Testing
  5. Pressure Testing the Radiator Cap
  6. Radiator Testing With Repco

Tools for the Job


  • Pressure tester kit
  • Safety goggles
  • Gloves
  • Coolant mixture compatible with the vehicle
  • Rag or towel

Preparing the Vehicle

Allow the engine to cool down completely before initiating the test to prevent burns from hot components. Park the vehicle on a level surface and engage the parking brake. Open the hood to access the radiator and cooling system components.

Identifying the Radiator Pressure Cap

Locate the radiator pressure cap, typically situated on the top of the radiator or on a separate reservoir. If unsure, refer to the vehicle manual for precise location instructions. Remove the pressure cap carefully to access the radiator.

Attaching the Pressure Tester

Select the appropriate adapter from the pressure tester kit that matches the radiator's cap opening. Attach the pressure tester to the radiator in place of the removed pressure cap. Ensure a secure and snug fit to prevent air leakage during the test.

Follow the pressure tester kit's instructions to pump air into the cooling system gradually. Monitor the pressure gauge on the tester to increase pressure steadily to the specified range recommended for the vehicle.

Inspections After Pressure Testing

There are several elements to check for after performing a radiator pressure test:

Inspecting for Pressure Drop

Once the desired pressure level is achieved, observe the pressure gauge closely for any signs of pressure drop. A noticeable drop in pressure indicates a potential leak within the cooling system that requires further investigation.

Checking for Leaks

Carefully inspect the entire cooling system, including hoses, connections, radiator, water pump, and heater core, for signs of leaks while the pressure is maintained. Look for any visible coolant leaks or hissing sounds indicating escaping air.

Examining External Components

Check external components like the radiator hoses, connections, and clamps for signs of wear, damage, or loose fittings that might contribute to leaks under pressure. Tighten or replace components as necessary.

Pressure Testing the Radiator Cap

To ensure the radiator cap maintains pressure effectively, perform a separate pressure test on the cap itself using the pressure tester kit. Replace the radiator cap if it fails to maintain the specified pressure.

After completing the inspection, release pressure from the cooling system using the pressure tester kit's release valve. Once the pressure is relieved, carefully detach the pressure tester from the radiator.

If any coolant was lost during the test or due to leaks, replenish the cooling system with the appropriate coolant mixture recommended for the vehicle. Ensure the radiator is filled to the proper level.

Once you are satisfied that the pressure test has been completed and all check have been performed, inspect the work area for any spilled coolant or tools and dispose of any used materials responsibly, then securely store the pressure tester kit.

Radiator Testing With Repco

We have a wide selection of radiators for sale at Repco, as well as radiator pressure testing kits and other tools that will help you perform radiator maintenance and check ups with ease. Head into your local Repco store or shop online and explore our full range.

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