How To Make A Cooling System Pressure Tester

Learning how to make a cooling system pressure tester can help you diagnose potential problems before they turn into big headaches. A pressure tester can help you pinpoint leaks that can occur within a vehicle’s cooling system. A professional pressure tester can cost up to $100 or more, depending on the brand, model and number of features, but you can get the job done with far less money by building your own cooling system pressure tester.

What you’ll need:

  • Tire pressure gauge
  • 2 valve stems
  • 5/16” plastic tee
  • Several lengths of 5/16” rubber fuel line hose
  • Angle iron
  • Small hose clamps
  • Bicycle pump
  1. Find a tire pressure gauge. A dial indicator tire pressure gauge with a long hose is ideal for this application. Remove the valve core from the end of the tire pressure gauge, as this portion will not be needed. Also sand away the expanded sections of the valve stems where they would normally fit into a steel rim.
  2. Assemble the pressure tester. Cut three pieces of the rubber fuel line hose. One should be about ten inches long while the other two pieces should be about three inches long. Attach the hoses to the plastic tee and secure them with small hose clamps. The ten inch piece should go to the radiator neck stopper. Insert a valve stem on the end of one of the two inch pieces. The tire gauge will be attached to the remaining two inch piece.
  3. Create a stopper for the radiator neck. Cut out a short cylinder of wood that can fit inside the neck of the radiator. Drill a hole in the cylinder and secure a valve stem in the hole with epoxy. Remove the valve core from the valve stem. You’ll also need a three inch piece of angle iron as a retainer for clamping the stopper to the radiator neck. Drill a hole in the center of the angle iron that is large enough to fit over the end of the valve stem in the wood cylinder. Place the angle iron on the stem, then attach and clamp the rubber hose.
  4. Attach the gauge to the cooling system. Wait until the car’s cooling system is sufficiently cool in order to avoid serious burns. Attach the stopper to the radiator neck, then attach a bicycle pump to the valve stem. Use the bicycle pump to pump air into the cooling system until the gauge reads fifteen psi. You will more than likely hear a hissing noise or moisture near where the leak is occurring. Keep an eye on the gauge – if the pressure drops by two or more psi within only a couple of minutes, it also may be evidence of a leak within the cooling system.
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