Gen 3 Prius Engine Coolant Recovery Tank Pressurized, head gasket?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Max Johns, Nov 16, 2019.

  1. Max Johns

    Max Johns New Member

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    Hello all, new to this forum and getting ready to possibly tackle a head gasket replace on my 2012 Prius. I have been doing some final testing to make sure the head gasket is the issue. I used a block tester to see if combustion gases were in cooling system and showed little or no trace of any. While performing this test and running the car awhile I check engine again and coolant recovery tank was completely full. I slowly started to crack the filler cap and quickly saw that it was highly pressurized. System was not very hot but I let it cool awhile and came back with system not very hot at all. Recovery tank still had a great deal of pressure. I removed air filter cooling lines and started squeezing hoses going to recovery tank and pressure seemed to release and go down. Kind of weird issue, could this be a clogged vent cap? Also this machine had a bunch of head gasket repair fluid installed not on my watch and could that be clogged up in system somewhere causing pressure to build? I believe the head gasket will need to go based on the reports I got from the person I bought car from and I am prepping for that but wanted to make sure I do not have an easier solution. I would also like to get the cooling system working well before I replace the head gasket if possible so it doesn't fry again. Thanks
     
  2. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    How many miles?
     
  3. Max Johns

    Max Johns New Member

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    213,000, oil is pretty clean on this one, lots of gasket sealer in the coolant. It does run pretty well with no engine codes at least for the short distances I have driven it. When I first got it I was getting misfire codes on cylinder 1 and 2. The person I bought it from said their mechanic saw coolant leaking in a cylinder with endoscope. I did a little disassembly of egr pipe which was mildly dirty and one gasket did appear to be slightly leaking but nothing drastic. My general thinking is if it has a decent chance of head gasket to start tearing into it and clean egr system and intake and if those look really bad to possibly reassemble and give it a try. I have all the head gasket and related gaskets ordered and also have a backup gen4 engine on hand in case I need to escalate the situation :)
     
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  4. cnc97

    cnc97 Senior Member

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    Coolant cap pressure is 19 PSI. It should release pretty quickly when the cap is loosened. But the cap could be holding extra pressure or the combustion gasses could be over-pressurizing the tank. Take the cap off and run your Prius in maintenance mode. If there are bubbles in your tank, the head gasket is the culprit.
     
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  5. cnc97

    cnc97 Senior Member

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    This is the equivalent of holding a grenade in your hand after pulling the pin, but you have no actual idea when the explosion is going to occur. You have multiple warning signs of impending trouble. This engine as it stands is simply a running core at this point. If you have the resources at hand, move on them now, in my opinion.
     
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  6. Max Johns

    Max Johns New Member

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    Thanks much for the input, that helps me to bite the bullet and dive in!
     
  7. PriusCamper

    PriusCamper Senior Member

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    Um, usually when an ICE fails it doesn't spread life killing shrapnel in every direction... No need to be an alarmist spreading unnecessary fears...
     
  8. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    Maybe just an allegory?
     
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  9. cnc97

    cnc97 Senior Member

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    My choice of description might be slightly alarmist, but I know from experience that “when” the failure occurs, it will be at the most inconvenient time that you can think of.
     
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  10. edthefox5

    edthefox5 Senior Member

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    YES.
     
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  11. Mendel Leisk

    Mendel Leisk Titanic Social Director

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  12. PriusCamper

    PriusCamper Senior Member

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    Yeah... Fear of the unknown is always a valid reason for caution... But once you read the error codes and the unknown becomes known it's possible, in some cases, to temporarily live with the red triangle knowing that it's not going to disable the vehicle.

    For example, I drive really old, rebuilt too many times battery packs to monitor how often the red triangle comes on from specific modules I'm on the hunt for. And the pack in my car right now has already had 7 modules replaced over the years and I'm reluctant to replace three more, hopefully my friends finds a way to buy the loaner pack in her car so we can retire this pack. About every 75 miles it'd throws a red triangle and I'd screenshot it and clear it with Dr. Prius while driving and just keep going, which is no big deal for me. Then as I had hoped, the situation deteriorated to the point it was throwing 3 red triangles a day. So I was going to pull the pack... Then, inexplicably... It hasn't thrown an error code all week over the course of 200 miles. Electrons are weird!!!

    In other words, some of us are quite comfortable with a hand grenade without the pin in our hand as just another ordinary day and we've not much of a concern about being stranded because with experience you're more likely to find a way to safely make it home.
     
  13. cnc97

    cnc97 Senior Member

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    Such are the nature of our “experienced” Prii or Priuses, one day they are ready to give up the ghost, and the next, they act like it’s day one again.

    All things considered, I’d buy mine again if I knew all that I would have to go thru.
     
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  14. Max Johns

    Max Johns New Member

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    Thanks guys, after diving into this head gasket issue deeper, I found after letting the car run awhile to get to temp, I did start getting exhaust gases in the coolant reservoir, so now I have the 100% surety that is the issue, so I guess the pin was pulled. A question related to cooling system, when car temp hits 180 or 190 thermostat should open right as I didn't see this happen, but maybe I needed to run it a bit longer. I'm hoping that this engine is still in pretty good shape to allow the head gasket repair to be successful. Started tearing into head and hoping to get new head gasket in this week. I was originally thinking to just swap out motor, but figured I would take a crack at trying the head gasket replace. Figured I don't have much to lose by trying it except my time.
     
  15. cnc97

    cnc97 Senior Member

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    The thermostat temp is listed as 180. So if you aren’t seeing signs that it’s open, then it might have failed. However, I can tell you the hottest temp I have ever seen in my car is 195. And that was after 4 1/2 hours on the highway at 65+mph. So if you aren’t getting any hotter, then it’s possible that yours is still good, and just not showing any flow.
     
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  16. PriusCamper

    PriusCamper Senior Member

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    Good for you for having a go at it!
    And good on you for already thinking of all the peripheral parts that might be wise to replace while you're in there.
    How much time are you able to give yourself? Do you have another vehicle to drive for as long as it takes to complete?

    I've found I do my best work with first time repair learning when I give myself lots of time to be super thorough and clean and inspect everything as it comes off the car. That way when it's time to reassemble everything is super clean and it's like assembling a brand new car instead of an old worn out greasy grimy one. I enjoy the experience way more that way too. But I'm kind of a neat freak like that!
     
  17. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    Running up a mountain will run the temp up real fast. (y)

    I do a partial grill block in winter, but make a point to pull it off if going up a serious hill.
     
  18. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    This video has a lot of good tips. They have some cringeworthy table manners, and some bits drive me up the wall. Like how they'd applied Form-In Place gasket to the timing chain cover, before they even start filming the scene, and the guy stands over it talking for about 2 minutes, before they even get around to looking where it goes. Repair Manual says the stuff should be out of the tube and the cover back on the car within 3 minutes, and all the bolts (roughly 25) torqued withing 15 minutes. Anway...



    Some repair manual excerpts attached:
     
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  19. padroo

    padroo Senior Member

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    Will you be replacing anything besides the head gasket?
     
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  20. PriusCamper

    PriusCamper Senior Member

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    Have you ever got temp data on difference between partial grill block vs no grill block?
     
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