I recently had the opportunity (read need) to replace the coolant expansion tank on my '06 CS Titanium due to the seal leaking. While the DIY write-up on Pelican Parts is certainly adequate I think they have you do more than necessary. So, below are the steps I took to replace mine.
Tools needed (may not be all inclusive as I'm doing this from memory): 12mm triple square driver, T30 & T15 torx bits, 16mm (or 5/8") socket, couple of extensions, blade screwdriver
1. Remove the beauty covers over the CET, in front of the passenger side MAF, and passenger side air pump. This gains you access to all the parts you need to remove to get to the CET.
2. Siphon any coolant from the tank. I used a clear plastic tube pushed down into the tank as far as it would go and sucked on it to get it started. Just like siphoning a gas tank (not that I ever did that...).
2. remove the air filter box.
a. remove the filter cover and filter. This requires disconnecting the cover from the MAF
b. remove the air box. This is held in by one bolt at the top front and two pins on the bottom. It takes a little effort to disconnect it from the air inlet and maneuver it out of the space.
3. Disconnect the torque arm at the frame mounting bracket and loosen it at the engine mount. This has a 16mm bolt and the 12mm triple square bolt. With it disconnected at the frame mount and loosened at the engine you can swing it out of the way.
4. Remove the torque arm frame mount bracket. This has two 16mm bolts. One near the engine, one at the back that is reachable with a socket and rachet. Pelican calls for removing the lamp assy, but this is not necessary at all.
5. With the torque mount bracket out of the way you can now remove the CET. Remove the hoses attached making sure to catch any additional coolant that may come out of the main hose and maneuver the lower (main) hose up and out of the way.
6. Remove the CET by pulling it forward and up. It has a mounting channel on the bottom that you have to pull it out of.
7. Assy is the reverse.
Once I was done with the installation I put in about 2 quarts of coolant to top it off. After driving it for a day I rechecked and added just a bit to bring it up to max as it had bled down to min during this time, which I expected it to do.
Here's a link to pics. http://s1172.photobucket.com/user/tjrobinson2000/library/Porsche Cayenne Unfortunately the pics I took are all 4mb or larger so I can't upload them directly.