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How To Replace Your Prius Water Valve

A sticking water valve is a common problem in 2004-2009 Prii, and it’s usually because of a malfunctioning water valve sensor. Once you know you have a failing sensor, you have to replace the entire water valve as soon as possible.


Image Credit: Stomper88

The good news is that you can buy an OEM water valve specifically designed for your Prius model and easily replace the malfunctioning one with this simple step-by-step tutorial. The entire process will take a total of 4-6 hours, and it’s a few hundred dollars cheaper than having a dealer replace it for you.

Tools You’ll Need

  • Phillips head screwdriver
  • Flat head screwdriver
  • Pliers
  • Tiny socket wrench or cable-operated hose clamp pliers
  • 10mm and 12mm deep sockets
  • Spill-free radiator fill kit (optional)

It’s strongly recommended that you wear safety goggles throughout the entire process to prevent coolant and dirt from getting into your eyes.

Steps to Take

The water valve is located in the front right side of the engine bay, underneath the engine. It’s a black three-way valve connected to the engine, heater core, and coolant heat storage tank. Take the following steps to remove the malfunctioning water valve and replace it with a new one:

  1. Remove the radiator cover and the under engine cover.
  2. Drain the coolant.
  3. Disconnect and remove the power connector from the valve.
  4. Remove the three hoses attached to the valve. Make sure the coolant drain pan is right underneath the valve because coolant will leak out.
  5. Use the 10mm and 12mm deep sockets to remove both valve mounting bolts.
  6. Remove the valve.
  7. Mount the new valve with the valve mounting bolts.
  8. Reattach the three hoses and the power connector.
  9. Refill the coolant.

A Few Useful Tips

We’ll close this post with a few tips:

  • Before starting, use a marker to mark the upper hose that’s connected to the water valve. It’s so you can differentiate between both upper hoses when everything’s dismantled.
  • It can be tricky and time-consuming to remove the three hoses connected to the valve, as they’re bound by spring clamps that are only accessible through a tight space. You can use the tiny socket wrench and deep sockets to reach the spring clamps, but it’s much quicker and easier to use cable-operated hose clamp pliers.
  • When refilling the coolant, be sure to do it correctly to avoid any spillage or contamination. There are plenty of tutorials and YouTube videos on how to do this.
Written by Jason Lancaster