I find the cause of my problem...finally!

The oil usage wasn't due to stuck oil rings?

Details on what was done to the motor please. My guesses.:

The cylinders were honed?
Slightly larger rings?
All valve seals replaced? (why not if the engine is already apart)
Big engine seals replaced? (ditto)
Rod bearings replaced (ditto)
Anything else?

Cost and time?

 

I am curious if you could actually see why it was burning oil.

Dogma for this car is that the oil burning results from the rings getting immobilized by carbon deposits.
Scored up pistons could also result in oil burning, although dogma is that this isn't the problem on a Prius.
Bad valve seals can also cause oil burning.

Were any of the rings stuck?
Was there any visible damage to the cylinder walls?
Were any of the valve seals damaged or heavily worn?

Your rebuild cost more than a used engine, but at least you know exactly what went back into your car, which is worth something.

 

Please just mark the photo with an arrow or something. I'm not sure what you are referring to.

There is a picture of a pack at a different angle here about 40% of the way down the page:

Toyota Prius Gen 2 Battery - Battery Design

You can see there that the white/yellow plastic on top at each end is where the metal rods that clamp the modules together attach. The black piece above it near the battery sure looks like an air dam. I don't know if they are all like that though. Some might have foam rubber in that location instead. Also I vaguely recall that the Gen 3 has the fan on the other side, and that doesn't have any block on top at that location because the air is supposed to flow through there. Oddly the top picture in the link above seems to be of a Gen 3 pack, since the fan is on the computer side.

The foam rubber pieces with the white tape on the side are also air dams. They also help hold cables in place.

 

100%. You need to find a replacement.

 

Which could be quite challenging. It might come down to fashioning one by carving it out of a block of plastic or dense foam, or 3D printing it. As discussed above expanding foam is likely to expand too far and block other parts of the ventilation. I suppose though one could put some cardboard around it, place the foam with the case top off, then carve that back to fit inside the case.

 

If the end of the battery (near the ecu) isn't fully sealed off, then airflow will "leak out" around the ecu sheetmetal instead of being forced through the battery modules.

So you need the black air dam, I think there's another on the bottom. Also need the foam pieces on the sides of the end module (they have white tape on the outside and are in line with the air dam).

Posted via the PriusChat mobile app.

 

Here's what I mean.

Posted via the PriusChat mobile app.

 

LOL.....that IS your problem. Not the cable, nothing else....that missing plastic piece is your overheating problem, since that is what forces the incoming air to change direction and go downward between each battery module. Without it, the air just continues straight across the top of the modules and out the ecu end of the case....THAT missing piece is a rookie move seen very often when DIY buys a new OEM battery and switches the components from their old battery to the new and forgets some of them. It's probably the most forgotten piece. The two black foam inserts on the sides are good to have, but as long as the foam strips on the upper case are present, they seal against the top edges of the modules=>very minimal cooling air leaks to the side area of the modules. The bottom plastic piece is important only because it keeps the "heated" air from entering the electronics compartment. It pretty much forces airflow to go into the exit ductwork and out of the car.

 

Verify that whatever you use is nonconducting. In the original position it probably doesn't matter but if bits of it break off you don't want any of it landing on conductors in the ECU area and shorting them.

Foam isn't always nonconducting. When people first started building replacement IMA packs for the Honda Civic Hybrid (2003-2005 model) some thought they could get away without heat shrinking the battery sticks. These sticks were mounted with the ends sticking out, back and forth, in a big foam block, which pretty much everybody assumed was nonconducting. That assumption was incorrect and some unpleasant excitement ensued.

 

Pretty sure you just insulated and cut off air flow to a module that already has weak temperature control. I think that one also has a temp sensor on the bottom. If you think you had temperature problems already, just wait for the alarms now..........

I'll never understand why it's too hard to fix something right. This is like a $5-10 part new from Toyo. A dime a dozen online ebay or craiglist or whatever. Probably free from a forum member.

 

I've built probably 500 Gen 2 batteries and probably forgotten more about the Gen 2 battery then most people will ever know.
The temp sensor on top is the incoming air temp. The three thermistors on the bottom are there for a reason. Because air flows downward through the gaps between the modules and the bottom is going to be the warmest. The module you covered with expanding foam is one of the LEAST airflow modules of the pack. Think about how much air flows over the top of each module, through the gap and under the bottom..
Your photo shows some foam you jammed into the air chamber to act as a backer for the expanding foam, except that backer foam is also past the closest module, which exposed that module to being covered by your expanding foam, which expands really really well. It's likely the first foam insert was pushed one or two modules even further back, potentially allowing the expanding foam to cover the first 2 or 3 modules and blocking the cooling air passages that allow air to flow down between the modules. regardless, good luck. It will certainly provide a Wth moment for whoever opens the battery pack in the future. I've had plenty of those moments, so this DIY repair doesn't surprise me much at all..Pretty sure there's a thread somewhere on the forum about these type of repairs being discovered by rebuilders who frequent this forum...kind of like a wall of shame...maybe this will be posted there sometime in the future. Because of a simple little piece of plastic.........