Legal disclaimer: This is my procedure and it is by no means the only way to install a cooler. You accept all responsibility for your own work. Don't blame me if you break your vehicle. This is simply a synopsis of my install.
*Do not use fuel hose. The additives in the transmission fluid can damage the fuel hose and contaminate the transmission or or cause the hose to rupture.
So here we go. I have had good success with B&M supercoolers on all my previous vehicles. They are stronger than the fin and tube type which can be easily damaged by road debri. Here's what comes with the kit from B&M: Cooler (1.5" thick), 5/16" transmission cooler hose(too small) and hardware for mounting. I ended up buying 3/8" cooler hose. Also in the picture is a Magnefine inline filter. These are unique because it has a large doughnut magnet at the inlet which attracts metallic bits that will damage the transmission and block passages and clogs valves. Then the fluid passes through a paper filter media like an oil filter. Should the filter ever clog, no worries, there is an internal safety bypass valve that will let fluid flow through the filter. These transmissions only have a screen in the pan so there's no reason to ever drop the pan. I spoke with several Toyota dealership parts departments and they all told me the same thing. A new strainer has to be ordered as its only stocked in CA because unless the transmission grenades, they have no reason to replace them. A clean transmission will last longer, so I use these inline filters. They are easy to install and easy to replace every 30,000.
Open the hood and remove the front fascia by popping the center rivet and lift out the fastener.
The cooler will be routed around the side of the radiator on the passenger side. There is a large cavity behind the headlight with nothing to rub against. There is also a wind dam between the front bumper and radiator. This is where the cooler hoses will be routed.
The rubber grommets (7/8") will protect the hose from rubbing and help stabilize the hose mid point between the cooler and radiator.
Its held by 3 tabs on the rear face. Press them forward to detach the wind dam and pull it out. I used a 7/8" spade drill bit to cut the holes for the grommets. It cut easily, just go slow at a medium speed.
You need to gain access to the radiator and AC condesor (in front of the radiator). Remove the top radiator support. remove the plastic air intake by removing two silver bolts and unplug the wire connection so you can lift it up and out of the way. There are 3 black bolts across the top of the radiator support and 2 bolts on the front ends. I suggest using a camera to keep images of where these bolts came from. Most are 10mm except for the 2 silver bolts beneath the radiator support which are 11 or 12mm. There are 2 phillips screws on the front of the bridge that connects the AC condensor to the radiator and 4 bolts across the back of this bridge. 2 hold the cooler lines and 2 attach the radiator fans to the radiator. Remove the 2 bolts that attached the hood latch to the top and bottom of the core support, disconnect the electrical connection behind the hood latch and you should be able to lift the top core support/hood latch up and forward out of the way. The bridge can be lfited up and back so you can now gain access between the condensor and radiator. It will be tight and you'll need small hands.
Be sure to use towels to protect the paint on the bumper. The AC condensor has unusually small spaces between the horizontal tubes. I used a very small phillips screw driver to create the holes in the fins. Lift the cooler into place and gently slide the screwdriver into one hole just far enough to pass thru the condensor (don't hit the radiator). Then wiggle the screwdriver left and right to make a space big enough for the plastic zip ties that come with the cooler (about 1/4") Don't go up and down. Do one hole at a time. Insert the zip tie into the first hole and place the cooler back in place on the zip tie. Then mark the next hole and repeat until all 4 holes are made.
Now you are ready to affix the cooler to the condensor. Put the foam pads on
the cooler between the cooler and condensor over the holes you chose for the zip ties. This keeps them from falling out and protects the condensor from the cooler. If everything lines up properly, run the fastens down the zip ties to permanently attach the cooler. The hard part is almost over. Put the radiator supports back on and reattach the air intake and hood latch assembly.
Now is a good time to install the filter and wind dam. The typical path for the trans fluid is into the top port and out the bottom port. I want the fluid to pass through the filter last so it will be attached to the bottom port fairly close to the cooler. Then route the hose through the bottom hole in the wind dam. With the hose pulled through the wind dam, reposition the wind dam into place.
Like I said the hard part is complete and now I'm taking a break because I didn't buy enough hose. I bought 4' of 3/8" transmssion hose from O'Reilys auto parts when I needed 6'. The hose that came with the cooler was 5/16" which is slightly smaller than the factory steel lines. I could have used the 5/16" but its a struggle to get it on the factory cooler lines. It probably adds resistance to the fluid flows as well. I will do a flush before adding the cooler to the circuit.
Flush is done. Link to: DIY Transmission flush on an '08 Sienna XLE
First things first. Before reconnecting the cooler line you need to identify the correct flow of the fluid through the radiator. I used the easiest line available to verify flow. Using the top radiator trans fluid line I disconnected the 5" shaped hose from the steel line above the radiator and attached a hose to each side. The hose needs to be long enough reach a gallon milk jug positioned behind the passenger headlight. This is strictly waste fluid collection.
Once you have the hose in place, you will need to start the engine for 3 seconds and shut it off. This will pump enough fluid out to see which hose is the ejection line. In the picture below, there is a black hose connected to the steel line and a clear hose connected to the top radiator port hose. The clear hose fit tightly inside the rubber hose. There's no back pressure so no need to use a clamp. In the picture below you can see the clear hose is now full of ATF. This is the ejection port for the radiator.
The fluid flows: Tansmission -> lower radiator port -> upper radiator port -> back to transmission.
This short hose will be removed entirely to connect the cooler back into the circuit.
Connect the cooler lines this way.
Route the hoses through the cavity behind the headlight and around to the top radiator port and steel transmission fluid return line. There is no modification needed to the steel lines. Just connect them with worm screw hose clamps. The factory clamps won't fit the new hose.
This is the finished install behind the radiator. Its hard to tell from stock.
Up front, the cooler gets connected with the top hose for the cooler input and the lower hose for the cooler output.
*Add 1/2 to 3/4 Quart ATF to compensate for the new cooler & filter and then check the dip stick before starting the engine. Start the engine and check the dip stick again adding ATF as needed. After running the engine for 5 minutes, check for leaks and fluid level. Test drive it for 15 minutes and recheck for leaks and fluid level. Lastly, new rubber hose tends to soften with a few heat cycles, so after 100 miles, remove the grill and re-tighten all the hose clamps one last time.