Changing engine coolant

It appears that the origianl NAD ruling is now behind a paywall. Too bad. As a substitute here is a news report of the event.

Rumple

 

An update to my post #22 in this string. Since my 2004 has 98.8K miles I decided to replace the engine coolant this morning (the inverter coolant had previously been changed when I replaced the inverter coolant pump as a preventive move last summer.)

I removed the electrical connector to the coolant heat recovery system pump and opened the canister drain. I left the radiator cap on so that vacuum would drain the coolant in the translucent overflow reservoir. Once the overflow reservoir was empty, I removed the radiator cap to encourage coolant flow.

~6.5 US quarts came out. I didn't bother to open the radiator drain since my prior experience was that nothing would come out of that drain. When I opened the engine block drain, only a tiny additional amount of coolant came out. There was some cloudiness in that coolant, maybe a bit of aluminum oxide?

After reconnecting the CHRS pump and replacing the LH engine undercover and the LF fender liner, I refilled the radiator with as much SLLC coolant as it would take (~3 quarts). I then put the Prius into inspection mode and set the heater temp to MAX HEAT so that coolant would flow into the heater core.

Something weird happened: sometimes the engine would respond to accelerator pedal input, but other times the engine would remain at idle speed, although the pedal was floored. Anyway, I continued to add coolant as the level in the radiator dropped.

After a while, I had reached the point of diminishing returns, but had only added 4 quarts total. I turned off the engine and took a break.

When I returned, I used a paper clip to short the switched terminals in the CHRS relay socket while the car was IG-OFF. This provides 12V to the CHRS pump.

That worked really well to move coolant into the CHRS canister, thus allowing more coolant to be added to the radiator. I ran the pump for 30 seconds at a time, then added coolant, then repeated 2x more. This allowed me to add another 2.5 quarts, so I felt I could declare victory. (Note that 30 seconds is the amount of time that the Toyota diagnostic laptop will run the pump. I don't advise that you run the pump longer than that period of time, as the motor may overheat.)

I took the car for a 30 mile drive without incident, and will check the coolant level after the engine has cooled down.

 

Clever... If you get a chance sometime would you be kind enough to put up a picture showing where to do this short across. I, and likely others, would be grateful.

 

I don't have a photo. However I'll describe this in some detail, hopefully you can follow along.

Find the relay box mounted to the cowl, over the engine. Remove the relay box cover.

The interior of the cover has a map showing the names of the various relays. Find the CHS relay which will be on the driver's side of the box (towards the inverter). Pry out the relay gently using a small flat-blade screwdriver.

You will note a pair of copper terminals and a pair of silver terminals on the relay bottom. The silver terminals are for the relay coil while the copper terminals are the switched terminals. I used a small paper clip to bridge the relay socket terminals that would mate with the copper terminals, to run the CHS pump. Do this when the car is IG-OFF, and don't run the pump more than 30 seconds at a time.

 

Yes, that was very helpful. I have identified the right one now and have saved this in my links to review before DIY projects on the Prius. I had saved this link Prius: 30k Service which suggests using a vacuum pump (both for radiator and inverter) but your method is easier and cheaper!

 

dont know if its been mentioned here, but what if one wants to bring the inverter coolant reservoir up to the full mark. can i just add distilled water? i only have 32k miles so i doubt i need a complete change, but i noticed the level is almost at the low mark..

 

I'd suggest you buy a gallon of Toyota SLLC and use that, rather than raise up the freeze point of the antifreeze by using water.

Also, if the coolant has dropped that much I'd also suggest you look for a leak.

 

I dont know if the level has dropped much if at all. I never really checked it before, but just the other day was snooping around the engine compartment noticed the level is not at full. For all I know it could have been there since it came from the dealer. I doubt it would take more than a few ounces to top off.

 

If you are a DIY then listen to Pat, you eventually will need a container of the right stuff anyway, H2O will absolutely dilute it. Not a threat in FL on freezing. But might interfere with proper cooling to the inverter.

 

Good advice. But, since it's still under original warranty, couldnt I let the dealer just top it and let them see if it's an actual warranty issue ie; leak?

 

Yes, you could.

 

And, you should.

 

And, maybe I would. But, I called the service manager and he said it's likely nothing other than typical coolant loss ie; evaporation, I mean we're talking maybe a couple ounces over 3 years, and they would top it off for free and I should keep an eye on it. I checked every possible leak point and there is no leak.

 

Sounds good. While looking for leaks, did you check the coolant drain plug on the transaxle bottom, the three hoses leading from the inverter, the three hoses on the transaxle, the bleed valve hidden under the large black plastic cover running over the radiator, and the inverter coolant pump behind the driver's side headlamp?

 

Yep, dry as a bone.

 

Just wanted to post pictures of how to get the electrical coolant pump to run during the bleeding procedure. As Patrick pointed out, you remove the blue relay from the "CHS W/P" slot at the far right, as shown in picture 1. The relay is marked Toyota 90987-02027 on the side and "Denso" on the top. A close up picture of the relay after removal from the socket is shown in picture 3.

After removing the relay you can jump the two upper horizontal contacts (metallic copper on the relay prongs, but tin colored in the relay socket) as shown in picture 2. I used a current meter, which will turn the pump on as well as give you a reading of the current flowing through the circuit. In this case it was reading about 3.6 Amps while the pump was running.

Update: I just finished draining, refilling and bleeding the engine coolant. I drained about 6 quarts and refilled with a little more than 6 quarts. I drained from the coolant storage tank only (did not open radiator or engine block drain). To refill, I used a funnel in the radiator filler neck and kept adding fluid a half a cup at a time. Then I squeezed the hose on the right side of the radiator (below the radiator vent plug) to force the trapped air to bubble out the radiator neck. I cycled the coolant storage pump for about 5-10 seconds at a time.
I repeated the whole fill, squeeze, pump cycling about 15 times to get the system filled up.
The current meter was a useful indicator of trapped air because it read 3.6 to 4.0 Amps after all the air was bled out, but read about 1 to 1.6 Amps before bleeding, presumably because it wasn't pumping much fluid.

 

I also added a very short (10s) movie on YouTube that shows actuation of the electric engine coolant pump:

This 10 second video shows how to actuate the electric coolant pump on a 2006 Toyota Prius. This procedure needs to be done during the engine coolant refill and bleed process to get all the trapped air out of the cooling system. This is the pump that the Toyota diagnostic laptop actuates during the "Active Test" mode to get the air bled out.
In the movie, I'm using a digital current meter (set on the 10A max current mode) to connect the two horizontal upper contacts on the "CHS W/S" relay socket. You can see the meter reading about 3.9 Amps as the pump is activated and hear the sound of the pump pumping coolant.


The photo attachments for the coolant pump relay:

 

An excellent idea to use your multimeter to measure the DC current draw of the pump (as long as the multimeter can handle 10A DC current; some have a lower capacity.)

Thanks for providing current readings when the pump is moving air, vs. when it is moving coolant. That provides an objective indication for the DIYer who may be unsure regarding whether air remains in the system or not.

 

Hi Steve,

Pls see the following message string:
http://priuschat.com/forums/gen-ii-prius-main-forum/71580-cant-get-inspection-mode.html

Inspection mode does not provide instrumentation, so you will not have visibility to coolant temp or any other operating metrics.