Help with doing pads and rotors in back.

Pad material will cause these problems.... Buy good Cermic pads and new rotors and you won't have that problem

First you want to remove brake fluid from brake resovoir, raise front wheels off ground and set park brake or block rear wheels. Remove front wheels, keep steering wheel unlocked so you can turn rotors side to side. Loosen bolts that hold caliper end gently pry caliper free from rotor, remove caliper and remove pads, use bungy cord to hang caliper away from rotor, have rotors measured to see if they are thick enough to have machined, replace if out of specs. Match up pads with old ones, use anti- squeak red liquid and put layer on back of pads, let dry. Use tool to put pistons back into calipers, slowly put pistons back into bore while opening up bleeder screw so ABS won't be damaged. After rotors resurfaced, wash with rubbing alchohal to remove any oils from hands, install rotors and reverse putting pads back onto caliper and reinstall, torque caliper bolts to factory specs and tighten bleeder screws. Install wheels, torque lug nuts to factory specs and replace brake fluid in resovoir. Lower car carefully to ground and press brake peddle without pumping it. Any air in system should bleed out, if not get someone to help with bleeding system. Road test to ensure no squeaks or pulling, burn brakes in slowly.

Front and back rotors are different. For front rotors, after you remove the wheel you need to remove the bolts holding the caliper to the mounting spindle. The bolt can be a standard 6 face head, a recessed hex, or even a torx or star head recessed bolt.

With bolts removed, the caliper can be worked away from the anti-rattle clips the caliper slides on. These clips are called "hardware" and should be replaced.

The caliper pistons need to be pressed back into position because the new pads are thicker than what you removed. The calipers should be tied and suspended and not allowed to hang by their brake lines while you work with the rotors. Use a "c" clamp and an old brake pad to press the pistons back in. Sometimes it is good to remove the cap on the Master cylinder to allow for brake fluid to travel back to the Master.

Either replace or turn the old rotors and then put the brake hardware in place. Lube the caliper slides. then as a unit position the pads into the caliper and hang the caliper over the rotor. The caliper will hang and pivot into place. Replace and tighten the mounting bolts.

The rear brakes are more of a problem due to a second set of Emergency brakes in rear assemblies. So you have 2 sets of rear brakes, the Emergencies requiring clearance to remove the rear rotors. Some car models require readjustment of the Emergency cables before reassembly.

In all, I would suggest that you be an observer for your first brake job. At least get a Video of the process at a number of autoparts stores. You can wind up with a car you can not drive or reassemble without help.

1. Put your car on a level spot for safety and start your car Sienna.
2. For left front rotor, turn your steering wheel to the left all the way and stop the engine. DO NOT put emergency brake on! Put stopping blocks on the passenger front front, rear right and rwear left for safety.
3. Half loosen all front left tire nuts and jack up the left front then loosen all nuts and take the wheel off.
4. Use a 3" G-clamp from Lowes, Home Depot or any store near you, press against brake cylinder so that brake fluid flows back to its reservoir
4. Remove one bolt on the caliper and the other bolt loosen and lift the caliper with the other bolt on and rest on a block. Do not take the rubber hose off nor attend to loosen any brake fluid pipes and nuts.
5. Remove brake pads and remove the nuts on the rotor, done.
If you need further assitance please let me know and if this assisted you please feel free to rate the solution accordingly. Thanks, Midwest-tek

Rear disc brake pads offer better performance and are not as affected by moisture like conventional brake shoe style brakes are. Rear disc brakes are similar to front disc brakes. The main difference is that rear disc brake systems must incorporate the emergency brake system. There are two methods widely used for the emergency brake with rear disc systems. The first system is a brake shoe inside the brake disc that is actuated by the emergency brake lever. The second is a screw style actuator inside the brake caliper. When activated the brake pads are forced into the brake disc and held tightly by the emergency brake lever.
READ COMPLETELY BEFORE STARTING
Step 1 - Identify Rear Disc Brake Components
Rear disc brake assembly includes; rear brake disc, rear brake pads, brake caliper mount and a caliper mounting screw. (Note: Some vehicles do not have the rotor mounting screw.)
Step 2 - Removing the Rear Brake Caliper Mount Bolts
To replace rear brake pads and rotors the rear brake caliper needs to be removed. First loosen the rear brake caliper mount bolts and remove them. Turn counter clockwise.
Step 3 - Lift Rear Brake Caliper from The Caliper Mount
After the caliper mount bolts have been removed, gently lift the brake caliper from the caliper mount. Inspect the caliper slides; they should move freely in the caliper mount. Remove rear brake pads and hardware.

Step 4 - Removing Caliper Mount Bolts
With a socket wrench or other appropriate removal tool, loosen the rear brake caliper mounting bolts. Remove bolts and lift the caliper mount and remove it from the vehicle. Remove the retaining screw from the disc mounting hole. Tap the rotor gently to release any rust that has accumulated between the rotor and bearing hub. Lift brake rotor from wheel hub holding on tightly, using both hands. You do not want to drop the rotor.

Step 5 - Removing Rear Brake Rotor
Remove the retaining screw from the disc mounting hole, tap the rotor gently to release any rust that has accumulated between the rotor and bearing hub. Lift brake rotor from wheel hub, hold on using both hands and do not drop.

Step 6 - Install New Brake Rotor
Check the new rotor against the old brake rotor to make sure they are the same size. Clean the mating surface on the wheel hub before the new brake rotor is installed. Reinstall rotor retainer screw.
Step 7 - Reset Rear Brake Caliper
Before new brake pads can be installed, the rear brake caliper must be reset. The reset tool winds the piston back into position so the new brake pads will fit. This style of brake caliper will not compress with a clamp tool; it can only be reset with the proper reset tool.
Step 8 - Reinstall Rear Caliper Mount and Install New Rear Brake Pads
After the caliper has been reset, reinstall caliper mounting bolts and make sure the bolts are tight. Then match up the old brake pads to the new brake pads. They should be exactly the same except, of course; the old ones will be worn out. Check the new brake pads for proper fit and install any brake hardware that is required.
Step 9 - Remount Rear Brake Caliper
Reinstall the brake caliper, align brake pad hardware and reinstall caliper mounting bolts. (Note: align the rear peg of the brake pad to the groove in the caliper piston.) Recheck and retighten all caliper and caliper mount bolts. Bleed brake system to relieve any air in the system. Before driving the vehicle, push the brake pedal down and let it up slowly. This operation forces the brake pads to travel to the brake rotors. DO NOT DRIVE VEHICLE until proper brake pedal operation resumes. When test driving vehicle listen for any unusual noises during the operation of the brakes.
WARNING! Always have the vehicle under inspection on level ground, in park with the emergency brake on. Always wear protective eyewear, gloves and necessary clothing before inspection or work begins. Never crank an engine over when anyone is near the battery or engine. Always have an operational fire extinguisher close by, obey all first aid instructions in the event of an injury. Never stand in front or behind a vehicle when cranked over or running. When engine is cranked over keep hands and clothing away from rotating components. Never move a car without proper brake pedal operation.

the emergency brake shoes have a star wheel adjuster that must be backed off to remove rotor

there should be adjustment under vehicle looks like bolt attached to cable just back off nut and loosen bolt 

You need to go into the access hole in the rotor and back off the park brake shoes, which are located inside the rotor.

Check the hardware for the drum emergency brake inside the the rear disc brakes, these pads are for your emergency brake, there should be an adjustment bolt that just sits between the two pads. Also, check the cables running to this set of pads to make sure they were connected properly. After you have checked the drum emergency brake, follow the cables in the undercarriage and look for the point at which they combine to another single cable, this is the point where the actual cable pressure adjustment is located.

You can't remove the rotors because the emergency brake is tight on the inside of the rotors. Make sure it's not engaged when you are working on the rear brakes. Block the front tires for saftey. Then you have to remove the rear calipers from the mounting brackets, there are two bolts that hold the calipers on. Make sure you hang the calipers securily with some wire so you don't damage the rubber brake line hose. Then you need to adjust the emergency parking brake shoes in order to remove the rotors. Theres a rubber plug on the backside of the rear hubs, once you look at the back of the hub you'll see the plug. It's on the top. Once you take out the plug, you need to use a screw driver to turn the star spindel. You need to turn the star spindel counter-clockwise in order to give yourself enough clearance to remove the rotors. The beauty of this design is that ford incorporated a drum and caliper system together, but it's difficult to take off the rotors if the emergency brake shoes are to tight. The inside of the rotors acts as the drums for the emergency brake system. I've done this and it's not that hard, but, I did have to replace the emergency brake shoes because they were worn out and the shoes fell off the metal backing plates when I finally got the rotors to come off. They only glued these shoes onto the backing plates, they don't rivet them so take your time getting the rotors off or you can damage the emergency brake shoes, but if you do they are cheap at napa. My service guide says to install the new rotors, use a couple of lug nuts to hold it on, then adjust the star spindal for the emergency brake all the way clockwise until you can't turn it anymore, then you must back it off 8 clicks counter-clockwise. Make sure the emergency brake is not engaged when you are doing this, the 8 clicks backwards compensates for when you do engage the parking brake because the shoes expands outwards. This adjustment sets the emergency brakes so they work properly. Once the emergency brake is properly set you can't remove the rear rotors, which is what your initial problem is. Then install the rubber plug back in the hole, put on the new pads and calipers and you're good to go.