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pH testing coolant.

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by messenger, Jun 1, 2015.

  1. messenger

    messenger Junior Member

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    I picked up a 2009 a couple of weeks ago (76,000 miles) off of craigslist, it was listed so cheap I thought it was a scam but it turned out to only be a couple of miles from my house so all was good.

    The records showed this car was into the Toyota dealer 5 months ago for a recall inverter pump replacement so I figured the inverter coolant was newish.

    Don't know if this pH test is indicative of older coolant but here it is.

    From left to right:
    Far left side is from the Prius radiator.
    Next over is from our 1993 Camry this has Prestone extended life in it and most likely has the same mileage on it as the Prius.
    Next is the coolant from the inverter reservoir.
    And on the right is new Zerex asian coolant.

    As you can see the newer Toyota coolant and the new Zerex coolant show a pH of around 8, the Prius radiator coolant shows a pH of around 7 and the Camry around 6.5

    I was expecting to see just the opposite but the coolant seems to age to a lower pH not higher ?

    Tim

    [​IMG]
     
    #1 messenger, Jun 1, 2015
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Yes, the coolant turns acidic as it ages, hence a lower pH reading.
     
    #2 Patrick Wong, Jun 1, 2015
  3. bisco

    bisco cookie crumbler

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    congrats on your new wheels!(y)
     
    #3 bisco, Jun 1, 2015
  4. messenger

    messenger Junior Member

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    Ahh I had it wrong I was thinking a lower number was more alkaline but just the opposite now I get it and yes time to change it along with the trans fluid.

    Thanks

    Tim
     
    #4 messenger, Jun 1, 2015
  5. exstudent

    exstudent Senior Member

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    Read post #11
    Fluids | PriusChat
    Most likely the inverter coolant was NOT drained/filled. Financial disincentives to do so.
     
    #5 exstudent, Jun 11, 2015
  6. SageBrush

    SageBrush Senior Member

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    Does the coolant in the reservoir cycle in normal use ?
     
    #6 SageBrush, Jun 11, 2015
  7. Mendel Leisk

    Mendel Leisk Senior Member

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    Just speculating: say the fluid level goes up/down maybe 1/4" due to temperature expansion. That's enough to keep the fluid roughly homogenized, albeit with a bit of a lag.

    I think the coolant in the reservoir circulates, albeit with some reluctance.
     
    #7 Mendel Leisk, Jun 11, 2015
  8. SageBrush

    SageBrush Senior Member

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    Then you think the pH differences OP found are an artefact?

    I did pH testing a few months ago with similar results to OP:

    #20

    As promised, pH testing:
    1. Coolant from Inverter Reservoir, ~ 50k miles use
    2. New Asian Zerex Coolant
    3. Ruby Red Grape-fruit Juice
    The strips are "URS-6L," made by teco diagnostics as a urine dipstick. The pH test is the second from the top and ranges from pH 5.0 on the far left to pH 8.5 on the far right. The test relies on color change of bromothymol blue and methyl red to pH. This is a variant of the 'universal indicator' method.

    Conclusions:
    1. Ruby Red Grapefruit juice is safe to drink, at least pH wise. The color change took time, so we are not reading the color of the juice. The strip appears to be working.
    2. New Asian Zerex Coolant is alkaline
    3. Used SLLC is slightly alkaline. Time to replace ? I think so.
    View attachment 71135 View attachment 71136 View attachment 71137
     
    #8 SageBrush, Jun 11, 2015
  9. 69shovlhed

    69shovlhed Surly tree hugger

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    and that's why you need to change it cause acid will eat up all the alloy in your cooling system. if your not gonna diy, just wait to your next service interval, no need for a special trip since its still alkaline
     
    #9 69shovlhed, Jun 11, 2015
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