Red Triangle Of Death, High Temp Light, Coolant Overflowing To Reservoir | Prius Diagnosis & Causes

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In this video, young mechanic Aiman discusses some of the possible causes to the Red Triangle of Death on the instrument cluster followed by High Temperature warning indicator icon sign on the center multi-function display on the dashboard. In Toyota Prius, the “red triangle of death” is similar to a check engine light on standard combustion vehicles. The warning light could be something as simple as a low oil pressure warning, or it could mean something more.

The problem diagnosis, possible causes and solutions pertains to Toyota Prius 2nd Generation (Gen II I4 1.5L Hybrid Synergy Drive) model years 2004, 2005, 2006, 2007, 2008 & 2009.

This video will be mostly discussing the potential problems and possible solutions as cooling system in any cars is very complex and each situation would be unique. But we hope this video could be useful to those trying to diagnose their own problems.

Aiman's dad bought this 2009 Toyota Prius from a friend who spent more than 6 months trying to figure out problem with coolant overflowing from radiator into the reservoir after driving at highway speed for more than say, 50+ miles. This will be followed by the Read Triangle of Death icon followed by High Temperature warning sign. After opening the hood he discovered that the coolant in the radiator overflowed into the reservoir. He cannot add the coolant into the reservoir because the bottle kept on spitting out coolant onto the ground it will not get sucked back into the radiator. He can only only add the coolant into the radiator. The problem only persisted when driving on the highway at highway speed. However, when driving stop-and-go on the back road, less coolant would overflow into the reservoir bottle. It could be over 1,000 miles and most of the coolant would remain in the radiator.

Some of the initial thoughts were that maybe this Prius had a blown head gasket or cracked head. He tested the combustion using the Block Tester, but the liquid did not change color. Engine oil also was clean and not murky, indicating no coolant leak into the block. If you don't want to purchase the chemical you can bring the car to your local auto garage repair shop or mechanic and they can test it for you.

One of the most common cause to overheating in Prius is the present of air bubbles in the ICE (Internal Combustion Engine) cooling system (not to be confused with the inverter cooling system). Prius is notorious with difficulty in getting rid of the air bubbles due to the Heat Storage Tank canister (CHRS) and difficulty getting the trapped air inside the heater core. Bleeding prius is a very time consuming process and has to be done carefully. CHRS has to be manually recycled and bleed properly using the upper radiator bleeder valve. We have a video on how to do that as well.

There's also a present of pressure when opening the radiator cap (when the engine is cool). Ordinarily there would not be a pressure when opening the radiator cap after the engine is cool because the coolant would be sucked back into the radiator. This usually happens when there is air bubbles in the system.

The air bubbles in the cooling system could also be caused by leaks in the hoses, pumps, and connectors, but Aiman's dad already pressure test the system and it was tight.

The previous owner already replaced the main electric water pump. In order to eliminate other potential problems, Aiman's dad replaced the thermostat and the radiator. This car has over 275,000 miles and most of these components needed to be replaced anyways. Besides, he bought the car dirt cheap and he can afford to replace these parts without causing too much of a dent in his pocket.

While diagnosing the problem, Aiman's dad found out that the Auxiliary Water Pump between CHRS and the heater core is not working. While driving during winter, he can hear the gurgling, swishing sound coming from the heater core inside the cabin which indicate the present of air bubbles inside the cooling system. We have a video on how to remove and replace the Auxiliary water pump. Since he has to replace the water pump he figured might as well he should replace the Coolant Control Valve as well even though there wasn't any error code associated with it (please note that 3-way coolant flow control valve malfunction usually followed by Error Code P1121). We've done many DYI repair videos for this Prius so please check our channel for videos which might be useful to you. We will list some of related videos below.

In this video, Aiman also explain how the ICE cooling system for Prius works. We had a hand-drawn diagram which is somewhat incorrect but we also provide the correct diagrams for the system.

Recording Date: November 25, 2018
Комментарии
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Aiman, Thank you, thank you, thank you. My (ex) mechanic had my '08 for FIVE days and still didn't get this air bubble problem fixed. My awesome wife found your videos on the subject and I fixed it myself in one afternoon. Along with your vids and a tune up it has never run better since I bought it two months ago. Thank you and God Bless.

TonyHendren
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You're a really smart dude. I liked your video. You made me aware of the issue on my car and it wasn't even this model of car. Thanks dude. I'm going to go look up how to bleed the air out of my cooling sysstem now.

MikeyMystery
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Gorgeous diagram Aiman! I feel supported and capable in addressing the error codes im reading. Having a list of what was tested and costs involved in the test supplies for help limit expenses.

difranophile
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Thank you for this video, my prius plug in has exact problem, I changed the termostat and still has the same problem. What did do for this problem if you help me please 🙏.
Thank you again

mahtabuddinsakhizdad
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2008 Prius hybrid has multiple water pumps. I learned first hand after dealership botched the replacement of the synergy drive system’s water pump, that it is very important to properly bleed the cooling and heating systems. Computer monitoring systems more sensitive than older cars. If you have intermittent Triangle, Check engine, and thermostat indicators check the reservoir. If it is empty with no leakage, odds are you have air trapped in the system.

scpanther
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I have exactly the same problem. Thank you for your advice!

eventurapr
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Hi Aiman, thank you for your informative videos and everything you do. In my 07 Standard prius, 20, 000 miles ago i replace the inverter and inverter pump because they both went bad...now i got the code to replace the coolant control valve ... i also have 275K miles at this moment, do you also reccomed to replace thermost and radiator as well ? Thank you again.

gabrielcabrera
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Thank you thank you thank you aiman this video was thoroughly informative thank you 🙏

_payan
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Seems like you had to do many unneeded repairs through the process of elimination to finally diagnose your problem. What’s the best way to diagnose your pressure issue (or auxiliary pump) problem without performing all the previous repairs (ex radiator, water pump…)?

nicoleancell
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Very helpful and useful video diagram was great as well

cristianosorto
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Hello, my Prius V 2013 with 190, 000 miles having the same issue. Overheat light comes on and goes off intermittently, after changing the Thermostat . I am pretty sure sir is not in the system because I got radiator coolant got flushed at the dealer, after replacing the thermostat. Could it be bad coolant temperature sensor ? ( I read a comment from very experienced technician that coolant temp sensor can misread the temperature and send wrong signal to the system, after undergoing overheat problem ). I really appreciate your reply. Also, will it be very expensive repair if I ignore this overheat sign and keep driving. It's coming only after 20 minutes of highway driving. I subscribed

kumara
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Great video very clear process of elimination precise thank you

paulnorris
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Have the exact problem now with all the symptoms! Two mechanics and the dealer couldnt figure it out.

UncleHoCM
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Very good video kid you are best we learned bcse you try to do it the best

jorgemora
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I have a Toyota hybrid I noticed I was very low on coolant and barely anything in my reservoir...just recently bought the car will that alert come on as well? I will put coolant in both ...

alixandria
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It's quite peculiar that it sounds like you righteously solved the air in coolant circuit with too much pressure problem there causing the overflow tank to not suck back in. And yet alls you solved is finding the very slow RPM pump and replaced it with a faster spinning RPM one. I saw your other Auxiliary Pump test video with the slow spinning RPM but did you ever even solve the coolant tank high pressure and not sucking back in issue. Explanation is in a black hole can someone get it out.

playfullysound
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How do you know the auxiliary water pump is dead did you test it? Is there a way you can test it? I test my in is spending so I’m not sure if is that. My question is if the auxiliary is dead can you test it?

hmongamericavang
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I guess I have air in the system somehow. I drove the car for several hours at a time (just got it a week ago, 2008 Prius) but never with heat on. I actually had A/C running most of the time. I think when I set my temperature yesterday it might have been set higher than outside, so I guess water got directed to the heater core. After 5 minutes I got a check engine light (P1150) and shortly after the red triangle & temp warning.
I noticed the coolant reservoir being full prior to that but didn't think anything bad about it because it stayed at 190F and didn't throw any failure codes.

Is it likely that my issue is somewhere between engine and radiator on the heater core cycle? Maybe the core or pump itself? I just hope it's not the head gasket...

fantscher
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People sell there prius here on craigslist when overheated

mryusuf
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Say you replace nothing. Will air bubbles still form? Do you need to bleed once a year?

Chris-goti