Stator Bad?

Okay so I finally got a chance to take the old Gen 1 for a drive with Torque and a Bluetooth OBDII attached (after the car sat idle for several months). For your reference, my original thread with some suspicions about what I thought the problem was is in the link below. However, as it is mostly about getting Torque to work I thought a new thread specific to the more likely issue was appropriate (P3120).

Trying to Diagnose Problem(s) With Gen1 | PriusChat

I had thought for a while that it might be an issue with the spark plugs or the PCV valve due to some rough running/idle of the engine whenever the "Triangle of Doom" appeared but with a code of P3120 now in hand I started to suspect the stator (I assume if MG2 is out of wack it could cause issues with how the engine runs?).

So with my son monitoring the Torque MG2 & MG1 Temperature readings we took the Prius for a short drive. I seem to recall that Torque is supposed to be able to log the readings but I couldn't get it to work right (any help on this would be appreciated) so we just observed the temps.

Both MG2 and MG1 started out a couple of degrees Celsius from each other (still need to set it up to convert the units to Fahrenheit).

However, not too far down the road (maybe just a few minutes into the drive) the temp of MG2 started climbing rapidly.

Max Temps We Saw: MG2 = 147 C, MG1 = 74 F

Does this mean drastic temperature difference pretty much guarantee that the MG2 Stator is fried/toast and should be replaced or do I need to keep diagnosing?

Additional Note: There is this high pitched whine when you let the car cost. The sound is especially noticeable when dropping from say 55 MPH to around 48 or 49 MPH. It has made this noise every since we bought the car so I hoped/assumed this was normal. However, my son's Prius (2006) doesn't ever make this noise. Is this sound normal for Gen1 or is it related to my issue (P3120)?

Other Tests I'm Considering:
* Test With a Megohmmeter:
I don't have one of these and they seem to be pretty expensive ($500+ for Fluke). I found one that will output up to 1000 volts and is only about $50.00 but I'm not sure it's good enough for my purposes (any advice/recommendations appreciated).

* Finger Test The Transmission Fluid
I know it's supposed to smell burnt. But how obvious is this? I've never smelled this fluid before so I'm not sure what "normal" should smell like.


Any advice and/or comments on any of the above is greatly appreciated!


Sincerely,
Vance

 

Just to clarify are you saying there are actually two issues?
1. Bad Transaxle
AND
2. Bad Stator

Or are you saying that these two symptoms: high pitched whine AND MG2 = 147 C, MG1 = 74 C (SORRY I meant degrees C NOT F) are both symptoms that mean there is a Bad Stator?

Thanks Again,
Vance

 

Hi Bob,
Excellent diagram and explanation of how the Prius hybrid system works. That really helps explain the whine. When I test drove the car I figured that whining noise might not be normal. Most people would probably cry at this point but I actually got the car for less than $2500.00 so if I can fix it economically enough I'll still be okay. First Gens in good working order go for around 4-6k in my neck of the woods.

So, can this be fixed just by replacing the stator or is there more extensive damage than that? How likely is it that the shorting stator caused any damage to other parts of the transaxle system?

As for the recording of the sound what would you need for quality. For example, someone holding a cell phone that was recording the whine and someone calling out speeds?

Thanks Again,
Vance