DIY - Coolant drain - B6/7 S4 and other similar engines

Why: Required step for doing most coolant and bigger repairs. Also a good maintenance item every two years because that is about the useable lifetime of Audi’s “lifetime” coolant.

Recommended Maintenance Interval:
Audi says that their coolant is a “lifetime” fluid but most of the time it should be changed every two years. A few ways to check if your coolant needs to be changed is by looking at it to see if it has turned orange instead of pink or purple. Or take a volt meter and dip the leads into the coolant tank to see how much voltage is present. If you see 0.5 volts or higher then the coolant needs to be changed.

Previous steps required:

  1. Jacking up the front end or driving onto ramps.
  2. Removing the belly pan, if there is one.

Parts Required:

  1. Coolant - Pink G12+ or Violet G12++ - can also use Lilac G13 but it is not compatible with the older G12 coolants. Most people get Pentosin since it is cheaper than the coolant from the dealership. I CAN NOT STRESS IT ENOUGH THAT ONLY AUDI COOLANTS LIKE G12+, G12++, OR G13 SHOULD BE USED! Other wise bad things happen fast.
  2. Water - preferably distilled but tap water works too.

Tools Required:

  1. 6 mm Allen key or socket and ratchet.
  2. Drain pan - needs to be able to hold at least two gallons.
  3. Vacuum coolant filler tool - not needed but highly recommended.


  1. Wait for engine to cool if it has been driven.
  2. Loosen the coolant tank cap slowly.
  3. Locate the thermostat housing on the bottom of the driver’s side front of the engine. There is a 6 mm Allen bolt that is facing down.
  4. Put drain pan under that bolt.
  5. Loosen coolant drain plug and watch the coolant drain out.

  1. Once the coolant is done draining then put the coolant drain plug back in.
  2. Fill with coolant - this is where the vacuum filling tool comes in handy to avoid air bubbles. It is not required though so you can just keep adding coolant and water until it is full and the coolant level doesn’t drop any more.
  3. Dispose of the coolant in an appropriate manner.
  4. Wonder why you waited so long to such an easy maintenance step.

I wanted to update this thread with the RS4 specific coolant drain but it will not let me modify the original post so here goes.

Basically it is the same procedure for the RS4 as the B6/7 S4s to drain the coolant but the RS4s use a plastic Phillips drain plug. See the picture below:

A word of warning though. The RS4 coolant drain plug has a notch cut into it so that it can slowly leak out coolant rather than fully draining out like with an oil change. You can either keep turning the drain plug until it is fully out or just let it slowly drain for about twenty to thirty minutes. Here is a picture to better explain:

Updated with picture of the RS4 coolant plug.

WOW always super work. Helpful stuff