A long time reading, first time contributing to the community.
This is a DIY for a coolant flush for the VW GTI MK5, something that for the life of me, I could not find anywhere else. If you're like me, you enjoying wrenching on your vehicles; especially the venerable MK5 platform. This DIY is incredibly easy with the right tools and materials available before you begin, but like you (Since you're reading this) I like to do my research before I begin and this should nudge you in the right direction. This was brought on by improper coolant being added to the system by a good intentioned loved one.
2.) Jack Stands (really only need one for the passenger side, but I like the extra room)
3.) T25 Torx for Belly pan removal
4.) Drain Pan
6.) Large Pliers for tension clamps
7.) 1 Gallon White Vinegar ($2.99, optional, more later)
8.) 3 Gallons Distilled water ($.99, Only need one unless pursuing optional portion)
9.) 3 1.5 liter containers of appropriate G12 grade coolant (Napa, Pentofrost G12 ++, $11 per 1.5 liters)
Time: 1 hour
1.) Begin by popping the hood and unscrewing the Reserve Coolant Tank in the top left corner of the engine bay. If your car is hot, let it cool down, a face full of steam does not a good day make.
2.) Chock the rear wheels, set the parking brake, and jack the vehicle up, and place the jack stands on the appropriate points on the vehicle. Use T25 Torx to remove belly pan. I tend to leave the jack on the working side - just in case.
3.) Here's where I stray from the Bentley Manual. While the method it states does work (I tried both to be sure), the way I'm about to show you gets the same results much easier and faster. Look for "Item 12 - Connecting Piece" below, it's in front of the oil pan. Remove the pressure clamp (Red Arrow) from the connector (Yellow Arrow). Notice the plastic hose clamp highlighted by the blue arrow; there is a screw within the red arrow that plastic piece mounts to. Don't forget to reattach it or your coolant line could rattle loose going down the highway. By draining the fluid from here, the lowest point in the system, you only have to unhook this connection, and don't risk breaking the radiator quick release or having to fight to get to it. You also get an extra .1 gallons this way along with less mess.
3.) Optional portion for contaminated systems such as mine. Mix white distilled vinegar and distilled water to the ratio of 50/50 and pour into the coolant reservoir. Leave the cap open until the end.
These globs of chunky mixed coolant mud were mixed until the vinegar got to it
4.) Start the car (Safety first, take it off the jacks) and allow the coolant to reach 90*C or the fans cycle, which ever comes first, adding 50/50 mix when needed. Drain, repeat until satisfied.
At the very least, the last cycle should be ONLY water to flush out the remaining vinegar. Various flushes (four total, left to right, replacement coolant right)
5.) Mix G12 ++ coolant with water at 40/60 for -13 F 50/50 for -31 F and 60/40 for -40 F. For 06 and 07 GTI's coolant capacity is 7.8 Liters/ 8 Quarts; for 08 and 09 GTI's coolant capacity is 8 Liters / 8.4 quarts. Add to reservoir with engine running until coolant mix is between min and max lines. Make a bit extra and go for a drive, stopping after the first 1/4 mile or so and adding coolant when needed. DO NOT OVERFILL. It's better to start out at the min and add when you get home that to fill it to the top and crack the reservoir.
6.) Enjoy. Check again in a week and add if needed. You could buy every item mentioned and have enough left over for a tank of gas with the money you saved.