Can Someone Tell What This Is?

I think that is some sort of transaxle vent. Hard to see under there but I think it is located on the upper transaxle or MG 1/2 housing. Just went and looked at mine and there is a little bit of oil, I assume to be W/S type fluid, around the exterior of the cap. Mine isn't that dirty though. Still, probably not an indication of a problem somewhere.

 

Oh yea... I read about that on some transmission fluid changing threads... It's designed to relieve pressure build up due to heat. I wonder if they've ever failed? I wonder how you remove them and test them to see if they're working correctly, or at least what the symptoms are if they aren't working correctly?

 

My theory, as I am not a licensed mechanic, is that it is designed to vent under positive conditions and I suspect NOT under negative conditions. In that regard, you should probably just keep the area clean and not worry about it. But then I think, when you pressed down the cap, of course testing the return spring tension, you may have pressed a bunch of gunk into the seal area, and over time it will creep into the seal and lead to compromise. It does look like there is a 10 or 12mm nut on the base of it, so careful removal from the housing would be possible. Then it could be properly cleaned and replaced (torque ?) and return your peace of mind.

 

Op how many miles on car? Have you ever had the trans fluid replaced? If not I would get on that.

 

Highway or mountainous driving isn't the issue, it's hot weather and driving your car the way a cab driver in a hurry would drive in the city that stresses/heats up a transmission. But in this case as far as I know what you're seeing with your tranny is entirely normal.

 

Yes, I would say steep mountain driving *is* a factor in my experience. That can get your transaxle temps up to 65C or more in hot weather. MG2 is working hard on those hills, both up and down. You want to use B mode there.

When I opened up my transaxle for refilling, a suction sound was heard as the plug loosened. The above vent is doing its job by releasing under high temps.

 

Wow... I see... That's a lot to ask from a little Prius!

 

Where is it exactly? Do I look for it above the hood or under the car? When I opened the transaxle fill plug I did not hear any vacuum suction hiss. Maybe because I tried to open and drain the transaxle while it was still warm? I hope I don't have a stuck/leaky vent - moisture could get in and ruin the innards!

 

Not likely, I would say. It's on top of the transaxle, probably not possible to see with the inverter in place?

 

The photo at the top of this thread shows the location...