Toyota 2004 Sienna repair: February 2013

2004 Toyota Sciena timing belt and water pump removal and installation notes:

There are more complete web sites and video's of this procedure, but I wanted to document a few points I figured out.

First of all see my post regarding the side mounting bracket flaw.

Next, the engine is mounted so close to the side wall of the engine bay that removing the rear cam gear to take off the timing belt cover back is difficult without the special tool to hold the cam gear. My solution was to not remove the rear timing gear and only loosen the rear cover so the water pump could be removed. I did this by removing the front timing gear with a powerful torque wrench. I then removed all of the bolts to the rear timing gear cover. The bolts behind the rear cam gear are accessible by rotating the cam. Do not be surprised when the cam gear springs uncoils and spins a bit. Just make sure you line up the timing marks and you will be fine. Once you get all of the rear timing gear cover bolts removed, it can be rotated around the rear timing gear so the water pump can be removed. It only needs to rotate a little to make way to slide out the water pump.

The other thing worth mentioning is that the crankshaft timing mark is on the top side of the crank. See my picture below.

The best tip ever from another site was to use electrical ties to hold the timing belt on the cam gears during installation. The rear cam gear and belt is nearly impossible to line up, so rotate it so you can see it, and then attach the electrical or zip tie around the cam gear and timing belt. Once you have the other marks lined up simply cut the zip ties.

Ok, so I completed changing my timing belt on my wife's 2004 Sienna mini van. Just prior to this, I replaced the timing belt on the 98 Sienna. The design of the newer van although a bit more stylish than the 98 has been given a few design flaws. Hopefully this blog will help others deal with the problem and maybe drop the hint to Toyota to fix this in the next version. Even with a few design flaws, it is far superior to most other cars, I have had the pleasure of fixing.

The flaw, I would like to mention today is the side mounting bolt bracket assembly. The side mounting bolts sit just in front of the top timing belt cover on the side of the V6 engine on the passenger side. They are used to connect the engine to the top of the area close to the strut tower. The bracket is composed of 2 aluminum pieces stacked on top of each other. The lower one bolts to the side of the engine. Two long vertical bolts thread into this piece. A shear pin is located between the bolts to keep the spacer bracket from sliding. The upper aluminum spacer bracket has two clearance holes. Also there is an additional threaded hole in the top of the bracket labeled #1 below. A final black steel bracket rests on top of the middle piece. The vertical bolts sandwich the 3 brackets together.

This design is nearly the same as the 98 with a couple exceptions. The outside of the black metal bracket is dished up. Picture below shows the bracket with clearance holes labeled 1 and 2. I am guessing this provides extra rigidity. Unfortunately, it acts as a funnel to route water and debris into the clearance holes for the vertical bolts. The bolt heads do not completely cover the slotted holes in the metal bracket. The slotted holes feed directly into the clearance holes in the middle bracket, which direct everything into the threaded lower bracket.

So I discovered this problem when trying to take the mounting bolts out. The front bolt came out with a significant amount of torque. The rear bolt failed in torsion, even after soaking it with PB blaster. Not only did the the bolt fail in the middle of the non-threaded shank, the middle aluminum bracket was still attached to the lower bracket. Crud in the clearance hole and remaining stud was holding onto the middle bracket. I ended up working it back and forth and twisting it around after raising it over the shear pin enough to get it loose. Once I removed the spacer section, I removed the lower bracket with the remaining broken bolt end attached. See picture below of the lower bracket with the sheared bolt attached. I put the bolt in my vice and turned the bracket and luckily was able to remove the bolt without damaging the lower bracket.

Se pictures of the bolt below. Note that this bolt came out of a suburban driven van, that is kept fairly clean.

To avoid the problem again, I would consider putting a small amount of RTV sealant in the slotted holes on the metal bracket. Also, I would grease the mounting bolts prior to installation.