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2008 Prius Overheating Issue

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Scott08, May 18, 2024.

  1. Scott08

    Scott08 New Member

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    Ok. So I've been dealing with a coolant overheating issue for a bit. I previously changed the water pump, which was leaking. I now realize that from the pump failing, air bubbles got into the system.

    So yesterday, I put in a new radiator cap and changed the thermostat. Using the Lisle funnel I took an hour in maintenance mode and did my best to get all the air out.

    Today, when I was driving, everything seemed fine at first. Then eventually the car began to overheat again.

    Here is what I am noticing.

    1. Most of the air bubble noises i have been hearing in the dash are gone. Except when I turn on the AC. When I initially start the AC I hear some sloshing in the dash.

    2. Yesterday, in maintenance mode the fans were clicking on at 96C like clockwork. Today, they are not coming on in temps over 100C. When I turn on the AC to check the fans, they turn on for about 10 seconds then click off. Then intermittently turn on and off.

    So, all in all...
    Is this normal fan behavior? If not, what could be the problem?

    Secondly, could the sloshing in the dash when I turn on the AC mean there is still air trapped in the system?

    Should I go for another bleeding/burping session? Or something else?

    Thank you.
     
  2. dolj

    dolj Senior Member

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    Check the level in the radiator (not the overflow tank) and see if the level is down. It is possible that trapped air has moved and now the radiator is low. You should be checking the level in the radiator first thing every day (when the coolant is cold) for at least a week to ensure any trapped air that has moved is replaced with (SLLC) coolant.
     
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  3. Scott08

    Scott08 New Member

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    I checked it this morning and it was good. I'll check again tomorrow.
     
  4. Tombukt2

    Tombukt2 Senior Member

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    The sloshing around in the dash maybe evaporative discharge from the air conditioner not escaping out of the drain line quick enough or at all I wouldn't really expect to hear coolant water sloshing around necessarily but if we're running the air conditioner and it's not able to drain quickly that would get pretty loud pretty quickly turning and moving the car or could so maybe check your drain tube on your air conditioning sometimes I poke something like a wire through it and then suck on it with my Shop-Vac hose generation 2's do not generally do any overheating.
     
  5. Scott08

    Scott08 New Member

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    There is water coming out of the drain line. And this noise it happening when the car is stationary.

    The coolant temps are getting over 120c and the problem light comes on. The car is definitely overheating.
     
  6. Scott08

    Scott08 New Member

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    Update. I checked the coolant level in the morning and it was down a bit. So I refilled and started burping it again.

    I noticed that when I was pushing the accelerator to the floor for an extended period of time that the coolant in the funnel would begin to rise significantly.

    Then when I looked at the cool and I noticed an oil sheen on top.

    So it's pretty clear my head gasket is blown. Now to figure out what to do to this car. Junk yard. Or try to get someone to fix the head gasket.
     
  7. Carall

    Carall Member

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  8. Scott08

    Scott08 New Member

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    Thank you for that thread.

    Last night I was driving the car, and the temps stayed fine the whole time(drove around 70 miles).

    Today, when I went out for a spin, them temps immediately started climbing. I managed to limp home without overheating, but in the process my check engine light came on and the the p1150 code.

    So I got the block tester to be sure, and sure enough it turned yellow and confirmed a blown head gasket.

    Since I only need the car to last me another 3 months and 10k miles, I decided to give the blue devil a shot after reading about the success story there.

    Since the coolant was new and I have a spare thermostat, I decided to add the blue devil as the instructions on the bottle.

    Somewhere near the end of the 50 minutes in maintenance mode I got a new p1121 code.

    After letting the car cool down for 6 hours, I decided to take the car on a test drive.

    Initially, when pressing the accelerator I was still hearing the sloshing sounds in the dash. But after about 5 minutes, they went away. (Hopefully a good sign)

    I only drove the car about 20 miles and went as fast as 20mph, but the temps stayed in a good range. One thing I was noticing that I never noticed before was the temps dropped really fast after accelerating. For example would drop from 96C to 80C in a few seconds. I don't know if this is good or bad, but never seen it before.

    The car is still a little low on coolant and needs to be bleed, but I ran out of new coolant through all this. So I hope to make it to the dealership tomorrow to pick up a gallon or 2.

    Then I will bleed it again properly and keep updating this thread on how it turns out.
     
  9. Scott08

    Scott08 New Member

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    Update.

    So I drove it to the dealership today to get some more coolant so I can fill and burp the system.

    The initial startup was really rough. So much so that it threw 3 misfire codes. Random misfire. Misfire cylinder 2. And misfire cylinder 4. Not sure if this is related to the blue devil or the p1121 3-way valve.

    Regardless, right now all I care about it the head gasket seal and overheating. I can deal with all these issues after I know the head gasket is sealed and the car is not going to overheat.

    Will keep the thread updated.
     
  10. Scott08

    Scott08 New Member

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    Update.

    Took it for another test drive last night. A little longer and a little further. Got speeds up to 55mph.

    Temps were running a little on the high side (got up to 101C) but still far from overheating.

    After checking the car afterwards, I noticed that the lower pipe was cold. So today I went to change the thermostat.

    And when I pulled it out it was heavily gunked up. All the blue devil got caught in the thermostat and seized it up.

    In hindsight, I should have put the blue devil in with a pulled thermostat and brand new coolant.

    But live and learn.

    I am still proceeding forward as I have no other option in the meantime. I am an uber driver, so i am out of work and cannot rent or use another car in my area. In other words, I got the time and a few hundred dollars to try and salvage this thing.

    Regardless, it seems like the head gasket is at least partially (if not all the way) sealed up for now.

    So I am going to replace the thermostat and 3-way valve today. Then do some more test drives. 17163293433197564127048036667775.jpg
     
  11. Tombukt2

    Tombukt2 Senior Member

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    Just cut the side plates off that thermostat top and throw the guts in the trash and put the plate back in and just close it up
     
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  12. Carall

    Carall Member

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    Not a problem.
    The owner of my Prius drives it by adding water.
     
    #12 Carall, May 21, 2024
    Last edited: May 21, 2024
  13. Scott08

    Scott08 New Member

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    Could you elaborate on the thinking behind that? And why that vs just closing it up without a thermostat in?
     
  14. Tombukt2

    Tombukt2 Senior Member

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    If you know anything about racing engines NASCAR any of that kind of stuff what you're creating when you cut the guts off the thermostat plate is a restrictor plate similar to what NASCAR put on throttle bodies and carburetors years ago. The restrictor plate is actually what keeps the engine at the right temperature and the amount of coolant flowing through that restrictor plate allows the coolant to dwell in the radiator and take the heat away at the radiator. When you remove the thermostat and leave that big 2-in hole water does not have enough time to dwell in the radiator remove the BTUs from the water and continue on its cycle instead the water flies through the radiator almost no heat gets removed and it just comes back to repeat that same silly cycle again slow the water down with the restrictor plate and the air has time to do its job basically now I'm sure some scientist will come along in a few minutes and use a bunch of big words like mayonnaise and there you go this is pretty simple stuff I would have just done that in the instance so I don't have to hop in the car and go down to the parts store to buy a whole thermostat I've got the pieces I need already gunked up with this pink crap I'm just going to cut the pink crap off dump the spring and now I have that 2-in plate with a 3/4 hole in it or whatever the thermostat guts took up in that space I just drop that back where the thermostat was a minute ago of course after cleaning and sucking all the pink crap out with my Shop-Vac bolt it back together and off I go No need to go buy anything but of course you're more than welcome to if that's just what you want to do that restrictor plate could stay in there 20 years and be fine forever they don't do this to cars because then there's something that they can't sell you remember The thermostat you need to have that because they said so.
     
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  15. Scott08

    Scott08 New Member

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    Thank you for that. That was a whole lot of information I didn't know. I appreciate it.

    I wish I would have done that before I added the blue devil. That makes the most sense to me instead of leaving it completely out, or putting it in and risking it getting gunked up.
     
  16. ChapmanF

    ChapmanF Senior Member

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    I'd wait for one of the scientists to come along before being sure you know it now. Isn't confirmed by much of what I can find in a quick search on heat exchanger transfer rates. Maybe there's already been some mayonnaise applied in this thread.
     
  17. Scott08

    Scott08 New Member

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    Ok. So today's update.

    Drained coolant, replaced thermostat, and bled coolant.

    Noticed while burping the coolant that the temperature would rise when not applying throttle, and then come down a bit when I pressed on the gas.

    Took it for a test drive of about 40 miles with speeds hitting 60mph. Stop and go driving.

    Temps stayed elevated again, but no where near overheating. Maxed out around 103C again. Same as when still, the temps rise when stopped and no throttle, and drop when accelerating.

    Afterwards, lower hose was warm(not hot) this time.

    So I am suspecting that the radiator is partially clogged. And maybe some other stuff too considering how bad the thermostat was gunked up.

    I can get a used radiator off an old prius for $50. The replacement didn't look the easiest though. And not sure if I'd have to replace fan assembly or fin assembly as well.

    Decisions decisions.

    I'll update when I decide, it might be a few days since I think I'm getting a rental so I can drive Uber for the holiday weekend.
     
  18. Tombukt2

    Tombukt2 Senior Member

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    If you're playing around with your radiator and all of that sometimes it's easier to take the fans off and run your hand across the hot radiator core while the engine is warmed up like after a run and see if you feel any cool spots usually they'll be in the middle of the radiator so all around the rectangle of the radiator you feel 150° heat let's say but in the middle it's dead cold that's common radiator plugging that can be rodded out with the top tank off. But giving the aluminum nature of the radiator may not be a thing or cost to seal back up. So there's always that I would imagine that that stuff you used in the cooling system probably did do something to the radiator plug up the middle very common this will certainly slow down cooling effects when there's no air flying into the front of the system so this may be a thing changing the radiators not too too bad You know there are two radiators you're changing one for the inverter and one for the engine but they're stacked on top of each other it's just easier to change them as a unit then drop the fans back on plug them up and let it rip Just put water in it initially You might be able to use the heat temperature gun and check your heat across the core but it still easier with the fans leaned back so you can see where you're aiming and if you get a lot better temperature across the core more stable than you're probably good no cool spot in the middle. The restrictor plate works well I've used it in cars 30 years ago and done it to my rear wheel drive Corollas and a few front drive Corollas in the early '90s especially down here in the south or you don't have to worry about extreme heating in the winter It just gives you full flow the minute you start the vehicle water's moving through the system at the pre-programmed rate that the calibrated hole will allow the coolant to flow It's usually a little better than with the guts blocking the hole and water having to be forced around it especially down here in the south or way out west where it's blazing hot It may or may not be the correct thing to do depending upon your take on the subject but it works very well and then you don't have a thermostat to break and unless you're living in extreme cold you'll never know that this is even been done and you'll never change a thermostat again.
     
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  19. Scott08

    Scott08 New Member

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    Update. So basically everything is running normal at this point, except when I am running the A/C.

    When the A/C is on, and I am pressing the gas pedal, there is bubbles in the coolant.

    When I am driving with the A/C on, the coolant gets pushed out of the overflow tank and it overflows.

    When the A/C is off, there are no bubbles and the coolant overflow tank stays within a normal range and I don't lose coolant.

    I got a borescope and am renting a pressure tool from advance auto parts and I am going to look for leaks and take a peak inside the cylinders to check out the head gasket.

    If anyone knows how the A/C system is introducing air into the coolant system, that would be great.