Transaxle oil change

Did you open a coolant drain plug ? Check the coolant container levels and replace with Toyota SLLC. You may have to purge air if the enough coolant was drained.

I do not follow where you put new WS into. Maybe you can grab a good picture and mark your tracks for further advice ?

 

I'm confused by your post.

You removed the inverter/transaxle coolant drain plug, which has a 24 mm hex head. Therefore, when you refilled via the reservoir, you should have used Toyota Super Long Life Coolant. Around 3 quarts of coolant will be needed if all of the original coolant drained out. I suggest you do a search to see how to purge air out of the coolant, which involves opening a bleed valve which is visible when you remove the black plastic cover over the radiator.

When you say that you "filled the rest through the side fill", what fluid did you use to fill? The correct fluid to use is Toyota ATF WS but very little fluid should have been needed since you did not remove the correct drain plug which has the 10 mm hex key hole.

The correct transaxle ATF fill plug faces the radiator. If you found another fill plug on the transaxle case, it was the wrong one to use.

 

Hobbit mentions that two holes exist to fill the transaxle: one facing the radiator like you mention, and another one on top. If OP put in WS, he either overfilled the transaxle or put WS in the wrong compartment.

 

Well, there actually are more than two, IIRC. I believe that one plug can be found on the side of the transaxle facing the driver's side front wheel.

It would be pretty tough to find the plug on top of the transaxle unless the inverter was removed first.

 

After reading OP's post again I think (?) he is saying that he recognized his mistake of draining coolant, so he replaced coolant first into the reservoir, and then through a different hole that is plugged by a 24 mm bolt.

If this is the correct reading, all he might need to do is purge air. However, his writing 'watery oil' draining out has me confused. Seems an odd description of SLLC.

 

I'm also a bit confused by the OP post. I just hope he didn't put ATF in the coolant loop or even worse visa-versa.

 

This is exactly why I posted a video of doing this just last week with a stern warning about not pulling the wrong plug:

http://priuschat.com/forums/gen-ii-prius-main-forum/92149-video-using-fluid-exchange-pump-transaxle.html

 

The coolant is nearly the same color as the ATF WS and coolant does have a kind of oily feel to it.

 

I nearly made the same mistake because the two bolts are the same, but I did research prior because even though I've worked on cars for 25 years and done just about everything you can imagine, the Prius is just different in a lot of ways. I just happened to run across this warning about the drain plug in another thread so I made sure to point it out in the video. BTW, if you use a fluid exchange pump or long funnel and go in through the side filler plug, you can't overfill the transaxle.