Procedure and first picture by dano0726, other pictures by drajac. For support on this writeup, please see this post in the VW TDI and Audi TDI forum.
Here are the part numbers: dual hose assembly (1K0-122-157-GH), two quick connectors that mount on the firewall (1K0-122-291-H [top] and 1K0-122-291-J [bottom] -- they have to be replaced) and one 3 liter container of VW Coolant (G-012-A8G-1G). Remember to mix the coolant with distilled water at a minimum of 50/50 or maximum of 70/30 ratio. All of this for just under $100...
In addition, I purchased 4 screw hose clamps to swap out those spring load hose clamps that VW installs from the factory.
Finally, buy a spring loaded hose clamp (from Sears/Craftsman). It is a major requirement to remove the 4 spring hose clamps as well as the air intake tube near the firewall (in order to reach both quick connectors on the firewall) -- don't even try to use needlenose/channel locks/other; the space is extremely tight for top and bottom hose clamps.
1. Get the Jetta elevated with ramps; I wouldn't recommend jack stands since you will be moving around alot underneath the engine bay area. Wear eye protection and old clothes (long sleeves) Have multiple flashlights ready to light up everything.
2. Crawl under the car and remove the plastic belly pan protector; get it out of the way.
3. Crawl back towards the firewall on the passenger side and look up. You will see the "space blanket" which is a heat shield and remove. See my picture. The 1st hose is connected there. Use your newly acquired spring loaded hose clamp to loosen and move upwards to pull off the hose. Get ready because you will get a face full (trust me here) of coolant dripping when you try to pull the hose. It took me a very long time to get it off (knife to cut away and scrape off). Now find the 2nd hose and repeat; it's higher up towards the center of the engine bay maybe 6 or 8 inches from the 1st hose. Look about 10 o'clock from the 1st hose. Take a well deserved break because you've earned it.
4. Get from underneath the car and remove the air intake tube -- it has 2 connections that must be removed and 2 more dreaded spring clamps. The front one is near the air filter, and the second one is towards the back near the firewall. There is a secondary plastic hose (sorry for my ignorance as to what is the mechanical terms here) on top of the fatter air intake tube that pulls apart. Once you get everything out of the way, you will see the 2 quick connectors on the firewall. There is a metal clip on each that needs to be removed as well as those spring hose clamps for the top of each hose.
5. Once you have removed the metal clip (do the top one first), take care of the spring hose clamp and remove the old hose; move it back some and repeat everything for the 2nd/lower quick connector. Install both new quick connectors in reverse order; bottom one first, then the top one.
6. Crawl back underneath and install your new dual hose assembly; I used the screw hose clamps instead of the spring clamps -- you decide, but it was easier for me to use a screwdriver and a socket to get all 4 tightened. Install the bottom fittings first and run the top up from underneath. Line up your clamps beforehand (as to how you want to tighten; remember the bad angles you have to deal with). I took my time with this step -- it could be fast or it could take a long time.
7. Now that you have both hoses connected (and clamped top and bottom) and have tested both quick connections, then re-install the "space blanket"/heat shield and clean up a little bit underneath.
8. Re-install the air intake tube assembly and connections and test for proper alignment.
9. Congratulate yourself -- you have saved yourself about $300/$400 in dealership labor!
10. Fill up the coolant reservoir (remember to mix 50/50 coolant to distilled water ratio) to "max" line and start the Jetta. I did this step 3 separate times, driving around the block a couple of times, then driving for longer periods of time on each occasion. I would watch the dashboard for coolant light and the temp gauge. Would return home and let the car cool down and repeat (filling up the coolant reservoir to the "max" line each time.
I plan on watching (over the next couple of days) the coolant reservoir and crawl underneath to recheck my 4 connections -- so far no leaks are spotted.
Here are drajac's notes and pictures
Noticed problem with leaking coolant while on vacation 500 miles away from home. Thanks to this and similar posts, I managed to get home (adding half a gallon of distilled water every 50 miles). Ordered hose assembly from a local dealer and thanks to dano0726's instructions replaced it today. Took me three hours to finish the job. Did not have spring loaded hose clamp tool but managed to remove the clamps with pliers. Also, did not replace quick connectors - not sure if and why they have to be replaced. 2nd hose was kind of melted and glued to the metal pipe, so I had to cut it and scrape it off with knife. Also, I had a little problem mounting air intake to the turbo; for some reason plastic intake at the end of air intake tube was not screwed in and came off with the tube. Here are some pics (click to enlarge)
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