Testing the Radiator Cap

• 1). Inspect the radiator cap for visual defects. Look for broken seals and push the spring on the bottom of the cap in. The spring should bounce back.
  
  
• 2). Moisten the seal on the cap with water. This will help it to seal during testing.
  
  
• 3). Install the radiator cap on the pressure tester adapter. The cap will screw on like it would into the radiator.
  
  
• 4). Install the cap and the adapter to the tester. They will attach as they would into the radiator.
  
  
• 5). Pump the tester to the recommended pounds indicated on the cap. You can pump higher than the indicated amount printed on the cap, and the pressure will release until it gets to the recommended pressure that is stamped on the cap.
  
  
• 6). Replace the cap if the cap does not hold pressure at or below the recommended amount.