Heat Retention, Coolant and Thermos

I believe that the coolant would not cool down any different then any other car. The recovery system thermos only holds approximately 3 liters of coolant. It is tied into the system similiar to having a heater core. Coolant is passed to the engine when the HV system is turned on & the engine is cold. Coolant is circulated into the bottle after the engine has reached operating temp. When full,the ECU will stop recovery. Also when the system is turned off ,when parking for example,and has not finished,it will continue for several seconds till it is finished.

 

I think what Tideland is getting at is the aluminum engine acts as a heat sink, rapidly cooling the coolant if the thermos wasn't used.

Aluminum has a very low specific heat (about 22% of water) and a very high thermal conductivity. This is why commercial heat sinks are often made of aluminum. I'm not certain what the specific

The engine will cool faster without the coolant, and the coolant will cool faster if left in the engine instead of the thermos.

 

Oh I see now

 

I wasn't aware that the coolant is sucked dry from the engine. I thought it was more of a fluid exchange.

 

Great question. From the Toyota documents I've read, I inferred that the majority of the coolant volume is actually pumped out of the engine and into the thermos. One of the reasons why the engine cannot start immediately upon turning on the car is because the coolant must be pumped out of the thermos.

If my model is correct, however, then the coolant pump is a critical failure point.

Rick, how the heck does this system work???

 

So the system immediately pumps coolant out of a hot aluminum block motor when it is at full operating temp?

I don't see how. Seems to me you would have a seriously warped block and/or head in short order. The ORNL description and illustrations didn't mention anything about the block being routinely drained.

When you Power On, the electric pump will pump warm coolant out of the thermos into the head to minimize cold start emissions. There is a bit of a delay in doing this before the ICE can start, which seems to depend more on ambient temp and SOC than the thermos.

If it's a nice summer day, no demand for Max Heat or rear defrost, you can Power On, wait for Ready, go into D and slowly drive off in Stealth. At -40, even if the SOC is green, the ICE will almost immediately start.

 

Hey guys - new here, Maybe I can shed a little light.

The thermos and engine are always full. No draining out or moving coolant from one place to another. The hot coolant in the thermos is opened up to the cold engine which does help heat the engine up faster, goes into closed loop faster, reduced emissions, better fuel economy.

The mixing of hot coolant with the cold coolant/engine is not so violent that would cause warping of metal block/head. Instead you get warm coolant in the engine and thermos. The water pump continues to circulate coolant thru the engine and thermos until both are up to temp. After the thermos temp is satisfied, the ECM closes the thermos valve so the water pump only circulates hot coolant thru the engine.

When you shut down, the engine cools off, and the thermos does not.
Rinse, lather, repeat...

 

Welcome prius mdt,

Not doubting your post, but do you have any corroborating links, etc. Or are you by chance a Prius Tech?
It’s a persnickety bunch here.

P.S. I hereby donate another point to double your PriusChat Point total to two . Again Welcome!

 

Ok guys(and any gals following) here goes.
You have an engine,heater core and coolant recovery bottle. There is a 3-way rotary valve connecting all 3. When the engine is cold,Power On but before start, a water pump activates to move hot coolant from the bottle to the engine & engine coolant will refill the space in the bottle.As the engine starts,the valve shuts off the flow during engine warm up and the system has normal operation with coolant circulating thru the heater core. When the engine reaches operating temperature the valve moves again to direct the coolant to both the recovery bottle and the heater core. When the bottle is filled with hot coolant the valve moves again to direct the coolant only thru the heater core,blocking the hot coolant in the bottle.
Any questions? Just ask,maybe I can explain a little better.This is explained in the 2nd gen NCF which has all kinds of interesting info :wink:

 

Ha! I checked your Profile and we have another Toyota Master Diagnostic Technician on board. Welcome Don!

 

After shutdown, does the valve rotate one last time and recharge the thermos? If not, what is that noise we hear after shutdown?

 

http://john1701a.com/prius/presentations/2...entation_38.htm

Page 38 to 41 shows good explanations.

Regards,
Ken@Japan

 

Thanks for the link,Ken. That shows a good explanation of what happens. Like they say," A picture is worth a thousand words" or something like that

 

Just an observation: If the coolant pump is running after I stop the car, the driver's side external door lock will not work until the pump stops. I have been monitoring this for quite awhile now...

Robert

 

Generically, this is a good presentation. However, there is actually another pump in the system. A pump is located/attached to the thermos bottle which is run only to empty and fill the thermos. This pump does not appear to run at any other time, and in my car if it was running in READY mode I would hear it based on the pump noise at shut off and start up. There are three pumps to this system: a mechanical pump within the engine (typical water pump) to circulate coolant when the engine is running; an electric pump which circulates coolant when the engine is not running to provide the heater function (actually circulates coolant through the engine as if the engine was running to take advantage of the heat transfer from the engine when it is not running); an electric pump which moves coolant to and from the thermos.

OK, evidence what I say is true? Dare I admit I was involved in a complete tear down of a 2004 vehicle? I am searching for the picture of this system, as it was quite evident the cooling system of this car is a bit more complicated and expensive than a radiator, a few hoses, and a water pump. Hoses and clamps and pipes etc. everywhere!

 

Hello Mark,
I agree there are three pumps.

This pump is shown in the presentation.

This pump is NOT shown in the presentation.

Regards,
Ken@Japan

 

Sufferin' - no links, just pullin this stuff out of my head - yes, I am another prius tech. One of the first - prius trained before they were available to the public. Been a Toyota Master Diagnostic Technician for about 10 years now. I've purty well figured out how these things work - my explainations tend to be simple.

Rick - how do I shed my "rookie prius poster" title for the "prius tech" title you display???