I haven't taken that cover plate off before but can't imagine it is much more than an assembly access cover. If it were me, I would drain the coolant and loosen the bolts enough (1/8" or so) and gently tap on the cover with a soft face hammer to break it loose.

Once that is done, it would be a matter of backing off the bolts (a little at a time) enough to see if the cover is holding something in or is just for access. I'm fairly certain that it is just a cover that can be pulled, cleaned and another bead of RTV added to it before bolting back into place.

After that, just fill it up and breath a sigh of relief....

 

Hey Georgiahybrid. My TCH has 146k miles. I was checking the hybrid coolant level and see that it has dropped below low, cold morning before starting engine. Is it ok just to add more fluid or would you recommend a fluid change?
If changing the fluid do I pour in exact same amount that came out or I should pour until I reach Max limit?
The coolant being low, does it indicate that anything else has to be checked?

 

The converter coolant is a closed system. If yours is low, that means it is going somewhere it shouldn't be (unless you have coolant stealing tweekers around your area). You need to find out where the leak is, fix that and change the coolant. As far as the level goes, make sure you add at least as much as what came out and (because of your leak) add enough to take it up to the flange of the reservoir similar to the last picture in the "how to".

 

Do you have a diagram of how the coolant flows, and how I can test it if there are leaks?

 

Take a look at the photos on the bottom of the first page of this thread. It is very obvious when you have a leak but you might need to look under and between components to see them. I use a video camera with a long flex head to help and if it is not obvious, try to find someone with an inspection camera that can help.

One thing that is cheap and easy if you plan on working on your car is to get a subscription to either Mitchel or All Data on the net for a single car subscription. I use AllDataDIY for our family cars and they are a complete, factory manual that is worth every penny of the cost the first time you use it.

That will show the entire cooling system for the invertor and will help you look for potential leaks.

 

Thanks for the DIY procedure for the inverter coolant change. One question is if the car should be off like I gathered from subsequent discussion, is the pump run using the 12V battery in the trunk?

 

You will need a bi-directional scan tool of some sort to power up the pump. The car is turned on by pushing the start button WITHOUT pressing the brake (Accessory mode) and the scanner is attached to the OBDII port and then the water pump is run using the 12 volt battery by the ECU

 

Can this be done by using the NAV (MFD) screen for those who have the XLS model, by putting the car into diagnostic mode?

 

I never have tried turning on the pump that way, have always used a scanner. I would look it up but I am in Manila right now and don't have the best of internet connections. Go ahead and try the maintenance mode BEFORE you do the change to make sure you can.

 

Can I do this without a scanner. Can I flush the coolant for inverter from the bottom fill up the reservoir and then put the car in fwd maintnce mode because the pump alway works when in that mode. I have seen someone on YouTube do that with Prius. Also u did coolant flush for radiator and now I have over heating issue can anyone help me. Tested thermostat was good. Burb the system put in fwd m mode and ran the water pump . When I drive the cAr it over heats when its idling it's ok