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Coolant warning light on RX8

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  • Coolant warning light on RX8

    Hi all RX8’ers, :smt006

    If your coolant low warning light comes on and off, even though you have sufficient coolant in the tank, here’s a fix that won’t costing you a cent, if you’re careful. I did this myself the other day as it was annoying me to no end having the light on.

    Step 1. Disconnect the battery and remove it from the engine bay along with its plastic shroud.
    Step 2. Syphon the coolant out of the coolant reservoir tank.
    Step 3. This is where you need to be careful. Disconnect all the hoses attached to the tank and disconnect the sensor.
    Step 4. Remove the tank from the engine bay.

    Now, if you turn the tank upside down and right up again you should notice little or no sound.
    That’s because the float inside the tank is stuck due to build-up of gunk over the years, as in my case.

    Step 5. Using a small flat screwdriver, pop out the sensor from its housing in the bottom of the tank. And put it in a safe place.
    Step 6. Get a large bucket or basin and fill it with hot water. Do this outdoors, see Step 8.
    Note: Don’t fill it to the top as you’ll be placing the coolant tank into it.

    Step 7. Crush a dishwasher detergent tab and pour into the coolant tank and submerge the tank into the hot water. Let it fill up and leave it for about 30 minutes.
    Step 8. Now lift the coolant tank out of the water and covering the lower 3 nozzles of the tank, as best you can with your finger/hands, shake the detergent water mix vigorously to get the remaining gunk build up dislodged. Now pour the mix in the coolant tank out.
    Step 9. Flush the tank out with hot water, then cold water.
    Step 10. Now test the tank to see if the float is cleaned & dislodged by turning the tank upside down and right-side up a couple of times. If you have cleaned it sufficiently you should hear, clunk, clink, clunk, and click.
    Step 11. Place the sensor back in the bottom of the tank. Now install the coolant tank back in the car. Remember to be careful when connecting the hoses back. Refill the coolant tank to the “Full Mark”. Put the battery shroud and battery back in and connect. Then away you go.
    I have driven over 300km since doing this and no more coolant warning light notices. To be sure, I syphoned off some of the coolant to the "Low" level and the light did come on. Topped up and drove around for a few Kms and light warning gone.
    Hope this is of use to any and all who have the same problem as I did.


  • #2
    Re: Coolant warnig light on RX8

    OR just disconnect the sensor and just keep an eye on the level :D


    • #3
      Re: Coolant warnig light on RX8

      Problem solved so chazz,handy info.
      I had it done under warranty as i read on here you could have done,thats about a year ago
      So it might be worth updating for someone.


      • #4
        Re: Coolant warning light on RX8

        Hi all,

        Just an update on the fix I did back in August re the Coolant Tank.
        To date I've clocked up 4,212 Kms since the fix and no issues. :D Zoom, Zoom!

        Originaly I disconnected the sensor instead of fixing the problem, but that was an NCT failure so my options were, fix or replace the tank.
        I went with the fix.

        Cheers. :smt006


        • #5
          Re: Coolant warnig light on RX8

          Why would it be a n NCT fail?just plug it back in and if the light is still on just tell the guy you need to top the coolant up,he'll be none the wiser


          • #6
            Re: Coolant warnig light on RX8

            Excellent guide there Chazz! :smt023 Kudos!


            • #7
              Re: Coolant warning light on RX8

              Good tip Chazz. Will try this when have time, sick of seeing that light for no reason.


              • #8
                Hi all,

                I decided to replace the coolant tank after all, seeing as it was so cheap from Mazmart Inc.
                Got the uprated tank with sensor and cap (13psi the old one is 0.9psi) for a total of €159, half of what Mazda charge.
                Just got to wait for a break in the weather to install it.
                Here's a photo of what you get for €159.


                Just checked their web site, the tank with sensor and cap is down today for €131 includes postage and import tax.

                While I was admiring my new tank a light bulb went off in my head. Ever notice how difficult it can be to see the Full and Low mark on the tank??
                So this is what I did. See photo below. When tank is filled to Full Mark Level, take a permanent marker and mark out a line for yourself on the front of the tank where the coolant is on the front of the tank. It'll be so much easier to see when the need arises.


                Last edited by Chazz; 14th February 2014, 06:02 PM. Reason: Update on price & a little tip.


                • #9
                  Thanks for the link, I'll be ordering mine soon :)