2010 prius cooling system issues

What's the miles, and how long have you had it?

 

You should use an OBD2 scan tool OR a Bluetooth dongle and use an app to monitor the engine coolant temperature.

Has the coolant in the plastic reservoir gone down?

When you said that you replaced the water pump with an OEM Aisin, I am assuming that you did not buy the OEM pump from a Toyota dealership. I think you still have a water pump problem.

 

Monitor the coolant temperature. Then you will know if it is a water pump problem.

 

^ That and check your coolant temperature sensor. It's actually a variable resistor, so a bad or corroded connection will affect it's output reading. Also inspect for rodent chew marks on your wiring harness.

Hope this helps......

Did you also compare hose temperature to radiator temperature with a laser temperature gun? Cold spots in the radiator would indicate a blockage. Make sure your electric cooling fans are operational also. Have you been changing the coolant every 50K miles, before replacing the water pump 4x?
One of the previous owners may have put a stop-leak product in the coolant and it's now clogging up the coolant pathways.

 

Sorry to bump this, but I, too, have a 2010 that I suspect has blockages or reduced coolant flow. I pulled the apparently original water pump and found some fairly large chunks (see photo). I replaced the pump and thermostat with Aisin. (Is there really an appreciable difference versus Toyota parts?) There were also some smaller chunks when I drained the system. The car is relatively new to me, so I'm guessing stop leak products at some point. Maybe hard water put into the system.

I'm wondering exactly where and how I would use a garden hose to flush. Looking through related threads I have a vague understanding of the gen III cooling system, thanks to rjparker and others. Car has 188k. No DTCs. I've driven it 10k. Suspect head gasket, but would like to know the best way to flush regardless.

 

Mixing incompatible coolants will also do that. It looks like a chunk of calcium, so hopefully just "hard water". That's why your suppose to only add distilled water to your coolant; if the Toyota or equivalent isn't available.
Old-timers usually say that it doesn't make a differences (dump anything into the radiator); but these newer cars' tolerances are so tight, not following OEM guidelines can eventually lead to what you've found. Damage is slow and incremental - plus you've already got 180K+ on it.

Just my 2-cents....

 

Thanks for that.

I also want to mention something related that I found because probably many haven't seen it: a guy was able to replace his heater core without removing the dash.

The description he wrote is pretty thorough. Video is from October 2024, but only has 1600 views.

 

Hmm ...

...you have to be willing to cut some insulation out of your way. You can cut it in a manor that you can just fold it out of the way and put it back when you're done so you can't even notice. Also, you'll need to pound the firewall out towards the engine bay just a little bit to gain the little bit of extra clearance needed to slide the old heater core out. Don't worry, it doesn't hurt anything and you really don't even notice.

The only other thing that you need to do is either cut or detach the hard aluminum pipes from the heater core that stick through the firewall, because you can't slide the core out with the pipes protruding through the firewall. When you put the new core in you'll need to cut or remove those ones too so you can slide the new core back in, then splice or reattach the pipes depending on the method you chose.​

... I guess I can see why a shop might not offer that option ....

 

Good Sir! Can you offer any pointers on where and how to use a garden hose to flush the gen III cooling system?

 

I don't know, I've never done it. Not sure I'd want to; the hose water might have more minerals or other stuff than I'd want in there, and it's hard to get all of the water out (or all of the whatever's in there back out), which means that, since the coolant Toyota sells is 50:50 premix, it would be difficult to refill the system afterward and end up with a 50:50 ratio.

 

Let's hypothetically say I'll use distilled water and a pump, then Mendel's suggestion to fill the system halfway with full strength coolant and top off with distilled. Given the chunks I've removed after water pump replacement and draining, it seems we need to stabilize the patient as a first priority.

 

Frustrating that Toyota Super Long Life Coolant only comes diluted. Yeah could be done with (full-strength) Long Life Coolant, but check availability, seems hard to find. Or a third-party equivalent?

 

Let me ask this: has anyone actually tried to flush the coolant system with a hose? Or does anyone know someone who has? If not, where exactly would you guess would be the best place(s) to put the hose?

 

I just purchased coolant concentrate from a Toyota dealer yesterday. around $36 for that gallon in Wisconsin.

op, are you losing coolant? have you considered a chemical test or other to see if there is a head gasket problem.

 

Thanks for that. Even if I have to order it, at least it's available.

I'm assuming there's a head gasket problem, but haven't done any tests yet.

 

Stop leak product, it's not hard water.

Exactly.

First things first. What symptoms are you having? Temperature lights? No heat in the cabin? Loss of coolant? Occasional severe rattling on engine starts?

If you have to do engine work the coolant passages could be checked then.

If a temperature light came on, one of two very reliable sensors reached 248f in an engine that normally runs 195f in summer traffic with 100f ambient and the ac on full blast.

Assuming no codes (you mentioned none) the first thing I would do is break out my Car Scanner app or Techstream and monitor both sensors.



If one was hot (215-248f or more) and the other was normal then you have an unusual sensor problem or no coolant at one of the sensors. Most likely both will be too hot after a complete warmup and drive.

Most of the small coolant hose devices are not going to overheat the engine even if they are completely blocked. No heater just means no coolant flow through the heater which could be clogged or there could be low coolant.

It's the big radiator hoses, the radiator, thermostat and engine water pump that are important.

Flushing - given you have a micro channel radiator it would be my first suspect. Reverse flushing is the only hope if it's clogged but is unlikely to work as unclogged channels would flow while clogged channels would not. But you might get an idea if it's flowing well in general before replacing it.

You could disconnect all the engine radiator hoses (not the inverter coolant hoses) and adapt your water hose to the biggest passenger side connection while plugging the smaller passenger side reservoir connection.

 

That link in my signature regarding flushing out stop-leak product has a recipe for a solution which "may" be effective.