Hi all - Master Tech here, but not seen this before. What is the gunk in the thermostat below from 2010 Toyota Prius? It’s everywhere - I had to pressurize system from the top to push gunk out to get coolant peacock valve on radiator to drain. Was the Toyota red coolant not changed in 212k miles? Or mixed with wrong coolant type? I’ve seen coolant head gasket ‘fixer’ before, but it was a lot different than this (but not in Toyota red coolant). Please people who know Toyotas or have seen this before. Overheat condition, low cabin heat, I believe due to mostly plugged heater core. Passed a cylinder leak down test, dry cylinders on bore scope, passed chemical head tester. I’m tempted to flush of everything - disconnect all hoses, flush them, individually flush block, radiator, and heater core…the stuff comes out relatively easy. But I don’t want to do the work if it’s head gasket fixer goop and the head gasket is gonna fail ‘again’ soon down the road.

https://preview.redd.it/htn4kpaaq63c1.png?width=1088&format=png&auto=webp&s=2a1f90460081b57d185aad780c15076a40b25b44

  • mycatsareloud@alien.topBEnglish
    1·
    10 months ago

    That is disgusting. Doesn’t look like old coolant stuff. Kinda looks like the coolant had a reaction with another one. If you google mixed coolant sludge it looks similar

  • Carvanasux@alien.topBEnglish
    1·
    10 months ago

    What color was the coolant that came out of it? Any chance there is a Firestone oil change sticker in it, or a service history there. I do several different types of vehicle inspections, including warranty inspections and liability inspections for Walmart and Firestone. I have seen Firestones universal coolant gel up and not play nice with several types of Oem coolant. I drive a ton, and have been driving and servicing high mileage Toyotas for the last 10 years. I have never seen Toyota coolant do that, even when it’s old. I have never used head gasket sealer in mine, and don’t think I’ve ever worked on a Toyota with it. I do know several models of pruis are know for head gasket issues though, so it is something to consider

    • meandering_muse@alien.topOPBEnglish
      1·
      10 months ago

      It was red/pink…but looked like it had just been changed. A lot of work had just been done on this car just before it was sold 225 miles ago, so I am very suspicious. New spark plugs, water pump, fresh coolant and oil change. I was amazed with a 3rd gen Prius the head gasket tested good.

  • Doomster9@alien.topBEnglish
    1·
    10 months ago

    This kind of looks like the crystalization of DEF fluid mixed in the coolant. Was there anything off about the color?