Hey fellow TDI owners...
I know this thread is old, but I just went through the removal of the thermostat assembly on my 2010 TDI Sportswagon and wanted to document the steps I went through. The notes and pictures in this thread assisted greatly, especially the picture showing the cocking of the thermostat assembly to remove it. I did this while changing my timing belt/water pump at 122k. Installation is the reverse of removal.
0. Remove the engine cover.
1. Disconnect the battery.
2. Drain the anti-freeze.
3. Removed the short intake feed hose from the throttle body to the lower connection.
4. Remove the three Throttle body bolts and upper dipstick tube mount bolt. You will need a new O-Ring when you re-mount the throttle body. Clean the Throttle body throat while you have it out.
5. Remove the large radiator hose from the bottom of the thermostat assembly and secure out of the way. This gives you clearance to remove the lower dipstick tube mounting screw.
6. Rotate back and forth and pull up to remove the dipstick tube from the engine hole. (Good opportunity to replace the tube's O-Ring at the engine end to prevent seepage)
7. Remove the remaining two hoses from the thermostat assembly. This leaves the one plastic tube still connected to the back of the thermostat assembly.
NOTE: replace all the spring hose clamps with quality hex head screw versions!
8. Remove the upper alternator bolt and loosen the lower one to rotate the top of the alternator toward the radiator side. This gives you the room needed to slide the thermostat assembly off of the horizontal plastic tube.
9. Remove the two thermostat assembly to engine mounting bolts.
NOTE: So far, I see no need to remove the screw securing the plastic anti-freeze tube that is behind the oil filter.
10. Reaching down with both hands, rock the thermostat assembly up and down to loosen it from the block, being careful to stop once it releases from the block.
11. Once loose from the engine, rotate the thermostat assembly on the plastic tube while sliding and cocking the mounting end towards the opening created by rotating the alternator forward. Please take your time with this step as you don't want to damage or crack the plastic tube. Once the thermostat assembly is loose, remove it from the top.
12. Clean the O-Ring sealing area on the block with fine sandpaper.
13. Lubricate the new O-Ring on the new thermostat assembly with fresh antifreeze along with the new seal on the plastic tube. Install the new thermostat assembly being careful not to roll either O-Rings out of their grooves.
The balance of the installation should be the reverse of removal...
Some of the hardest parts of the procedure were:
1. Coolant host spring clamp removal. I borrowed a friends clamp removal tool that has a cable between the handle and the action end. That's why I recommend replacing these clamps with a good quality screw type.
2. Breaking the seal on the hoses. I used a hand tool made for loosing hoses which has a odd angled "ice pick" end to get in between the hose and the seal. Once you get one section loose, twisting the hose will usually finished up the removal.
3. Once the upper alternator bolt was removed and the lower one was loosened, it still didn't want to rotate. My pry bar had to assist to rotate it.
4. Getting the thermostat out of the block. I had to use a long pry bar from the top of the engine between the upper thermostat assembly and the block to "encourage" it to separate from the block.
It wasn't easy, but up to this point, not impossible either. Budget at least a day or so. This is one job that you don't want to rush through!
Once the new O-Rings for the dipstick tube and plastic horizontal tube arrive, I'll re-assemble. I'll update this thread once done...
Hope this helps!