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

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.

1) https://youtu.be/Hsi79c9i9q0 - How To Replace Engine Auxiliary Water Pump Toyota Prius Hybrid Gen II 2004-2009 DYI | Part 1 Removal

Recording Date: November 25, 2018
Video URL: https://youtu.be/pRfn2GiMGzk

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