Head gasket blown. Pink/orange tapioca. Have a few questions as to cleanup before proceeding.

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by weapon, Jun 22, 2026 at 3:13 PM.

  1. weapon

    weapon Junior Member

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    Oil level is fine and clean. Although it does burn oil and there is oil residue on the outside of the engine. I believe it is a blown head gasket but want to make sure.
     
  2. rjparker

    rjparker Tu Humilde Sirviente

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    A quality borescope inspection on a cold engine with a manually pressurized and full cooling system is the better hg test.
     
    #22 rjparker, Jun 25, 2026 at 11:01 AM
    Last edited: Jun 25, 2026 at 11:23 AM
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  3. weapon

    weapon Junior Member

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    This is the one, but if it is not correct for the prius then I will take it back. I have never used one before.
     

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  4. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Something is not adding up? Maybe what’s in the cooling system is not motor oil? Have you ever changed engine coolant, any details?
     
  5. Mendel Leisk

    Mendel Leisk MMX GEN III

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  6. weapon

    weapon Junior Member

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    I am trying to flush the system not take it out for a road trip. Fill it with water, get it to operating temp then dump. Rinse and repeat until i get all of it out. Not going to do that 10 times with $40 a gallon toyota coolant. haha.

    I need to figure out a methodical process and that is why I am here for some help with planning assistance before I say screw it and just rebuild the head gasket or put a new engine in.

    Since I have cleaned the goop out of the easily accessed locations, next up is the harder places. What should be my next plan after the rinse and fill session?
     
  7. rjparker

    rjparker Tu Humilde Sirviente

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    If you don't see the fluid moving through the reservoir the thermostat has not opened.

    When the thermostat opens fluid flows through everything including the heater.
     
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  8. Mendel Leisk

    Mendel Leisk MMX GEN III

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  9. weapon

    weapon Junior Member

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    Yeah I am getting a lot of conflicting "help" so I am more confused than before. But that is ok. I have two of these so I am driving my alternate prius and big red is parked until i figure out a plan of attack.

    I have never changed the coolant in either but I had planned on doing all of the recommended maintenance on both cars which started last month. I have changed the oil regularly and done the trans fluid change in the spring. So I began on "my boy blue" with the egr cooler/manifold deep clean and that is when I noticed the new goop in big red after the check engine light came on. Parked it right away and came here to help diagnose.

    Wish I had a fellow prius enthusiast close to swing over and talk things through.
     
  10. Mendel Leisk

    Mendel Leisk MMX GEN III

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    So when you acquired the red one, someone else was the last to replace the engine coolant?
     
  11. weapon

    weapon Junior Member

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    This would be best cast scenario. The full system flush (multiple time) is my next step not matter what we talk about. That will start today as we dropped 15 degrees in daytime temp due to a cloud system moving in.

    Should I pull the water pump before hand and check to see if the goop is that low in the system? The bonus of the issue seem to be so far that the goop rose to the top and was in the high points. I used the syphon pump to get it out of the hose until is started sucking only pink coolant.
     
  12. weapon

    weapon Junior Member

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    I have no idea on maintenance by previous owner but it only had 70k miles and was in perfect operating condition as I paid for it to be checked by the dealership before purchase. As far as I know the coolant has never been changed.
     
  13. Mendel Leisk

    Mendel Leisk MMX GEN III

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    After initial 100k miles or 10 years (whichever comes first), it is supposed to be changed every 5 years or 50k miles.
     
  14. weapon

    weapon Junior Member

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    Good call. There has been no pink coolant come into reservoir since i added the water so it is still clear. I only drove it around my neighborhood for a few minutes then parked it and left it running so not sure if that was enough. Today my plan is to drive a bit longer and see if the flow happens.

    What do you suggest?
     
  15. weapon

    weapon Junior Member

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    That did not happen. (n) But it will be kept up to date from here on out.
     
    #35 weapon, Jun 25, 2026 at 11:53 AM
    Last edited: Jun 25, 2026 at 12:51 PM
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  16. weapon

    weapon Junior Member

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    Do you think I should put it in maintenance mode and cycle the water/coolant through the systems to see if the goop is throughout the system?
     
  17. rjparker

    rjparker Tu Humilde Sirviente

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    You need a scanner showing engine temperature as you drive with ac on. I can usually get normal temperature in 5 minutes. You can then see the flow entering the top reservoir hose using a flashlight.

    gen3 coolant reservoir flow.jpeg

    If you reach 200f or higher and no flow your engine is clogged up and or the water pump has failed. Normally the water pump would code.
     
    #37 rjparker, Jun 25, 2026 at 2:08 PM
    Last edited: Jun 25, 2026 at 2:32 PM
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  18. weapon

    weapon Junior Member

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    Todays update: Took big red for a nice long drive with lots of stops and starts over a few hours (all within striking distance of home base). The flow has restarted and the coolant has mixed with the water to a light pink with no goop in sight. No check engine light and is running perfect on the diluted solution.

    So my up to date plan is to do a full coolant refresh, Remove the reservoir, clean that again in the ultrasonic then monitor and see if this goop appears again. I will also swap in a cleaned egr cooler and manifold.

    Still do not know how the goop got started, maybe there was a small amount of improper coolant in there and it just took years for it to congeal. But I am at a loss.

    I have a full head gasket kit sitting in the garage just in case. Will keep updating.
     

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    #38 weapon, Jun 25, 2026 at 5:12 PM
    Last edited: Jun 25, 2026 at 6:08 PM
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  19. ASRDogman

    ASRDogman Senior Member

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    "Then put is all back together and filled it up with just plain water. I drove it around the block a few times and left the car running for a few hours in the heat just to see if any more goop came into the reservoir.

    Tomorrow I will drive it a bit further and run it a bit longer to get a better idea. I will then use the head gasket leak tester to check if I truly have a blown gasket. If that comes up clean, I will flush the system and replace the coolant with Toyota long life and monitor."

    You said you drove the car...Post 16.

    Post 29: I have never changed the coolant in either but I had planned on doing all of the recommended maintenance on both cars
    It does wear out, it breaks down. That could be the reason for the color, not oil.

    Post 32. As far as I know the coolant has never been changed.

    Post 34 I only drove it around my neighborhood for a few minutes then parked it and left it running so not sure if that was enough. Today my plan is to drive a bit longer and see if the flow happens. It's not flowing?????

    Post 38 :confused::eek:
    More driving with just water, the "flow" "restarted"? All that driving and it wasn't flowing?????
    "Still do not know how the goop got started, maybe there was a small amount of improper coolant in there and it just took years for it to congeal." You had said no one put any coolant in it?
    It wouldn't take much.
    And the coolant has never been changed?

    When you don't give the FULL information, it's hard to make a correct diagnoses....
    It just confuses people and give incorrect answers. Then you are more confused....
     
  20. weapon

    weapon Junior Member

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    You think you are confused , you need to look at it from my point of view. HAHA
    Have to read the replies to multiple people in the correct order, if possible. Which can be confusing on its own with all the injections of off topic questions, theories and multiple conversations going at the same time. I have no idea what is going on so I am trying to just answer to the multiple possibilities.

    Here is a tighter synopsis:
    I noticed the goop when a check engine light came on (dirty air MAF sensor code). I was in the process of getting ready to perform all of the neglected maintenance for my 2 prius(s). The majority of the goop was floating on the top level of the reservoir. I parked the car and started to diagnose. I used a syphon pump to suck the goop out of the reservoir until there was just dirty pink coolant. I pinched off the 2 hoses that lead to the reservoir so the system still had coolant in it. I then used the ultrasonic to throughly clean the reservoir. Reinstalled and then filled it with water to get it back to the correct level since i was going to do a complete flush anyway and did not want to waste $30 of new coolant to do it. The water stayed clear in the reservoir while i ran the car around my neighborhood on few short laps. It did not do what I wanted which was to circulate the system and push any goop to the surface. So I decided to take it out for a longer trip today as it was worth the risk to me. I drove around doing errands, stopping/starting, engine on/off, Idling and driving. At each stop I popped the hood and checked on the system. The coolant did mix with the water and the reservoir became a light pink (too much water to coolant ratio now). There was some minimal goop residue that made its way to the reservoir. So I returned home and removed the reservoir again and cleaned it one more time in the ultrasonic, I also cleaned the hoses as far as I could without taking apart the whole system yet. Now we are up to date.

    At no time has there been a consensus idea of what is happening from the group or someone who has seen this before, just a bunch of educated guesses (which i do appreciate the comments, still it is confusing) but I am listening to all possibilities and not ruling anything out at this point.

    Some suggest that incorrect coolant was added. I am the second owner but have owned it for over 10 years and bought it at 70k miles so the coolant has never been flushed as far as I know. That does not mean that coolant has not been added to keep the system full but I only used the toyota long life. And it has never been in the shop/dealership since I have owned it as It has had no problems up until this issue. Could that coolant in the toyota jug been bad or contaminated while it sat on the shelf for years. Maybe?

    Some think it is a stop leak but again that is not really possible unless it was done by the original owner over 10 years ago and took that long to reveal itself. Again not likely.

    If you look at the photo of the milk jug, it is separating like oil and water. The goop is oily and makes my hands slick. That is why I assumed it was a head gasket and oil was mixing with the coolant. But there is no coolant in the oil pan, just oily substance in the coolant reservoir.

    So I have decided after all the testing and cleaning that I will flush the whole cooling system. If there is more goop that come out during the flush then we know it is deeper in more parts of the system (right now it seems to only be in the reservoir and down the adjacent hoses a few inches but that makes no sense). The coolant change needed to happen either way. But if it is just residue, then I will run it as usual since it is not throwing any codes and the engine is performing solid. A cleaned egr cooler and manifold will be installed at this time also as those are already on my bench and ready to go.

    At that point I will monitor closely and wait to see if it happens again. I do have the gasket kit on the bench ready if it truly is a head gasket failure.

    Either way, I am still up for listening to more theories as I continue to clean the systems.

    Thanks in advance.
     
    #40 weapon, Jun 26, 2026 at 12:21 AM
    Last edited: Jun 26, 2026 at 12:43 AM
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