Burning coolant smell inside the cabin? Sweet burning smell that leads to a sudden craving for pancakes when stopped at a light? Phantom coolant loss? You may be eligible to join an exclusive club that the Audi engineers have forsaken, doomed to replace a  part that is barely accessible by mere mortals. Typical shops would charge about $350-500 dollars to replace the coolant flange, but you can do it with some patience and the right tools in a day, all for about $50.

The part in question is OEM part # 06D121132C, as you can see it is supposed to look like a 3 prong octopus. This tends to be what it looks like when people remove the flange during replacement, the neck breaks off in the block and leaves behind any sealing capability it once had.


Tools/misc. Required:


Tools/misc. recommended:

  • 2 x Part # N90316802 CTS/Heater hose o-ring (may as well)
  • 2x Mfg Part # 058121687 (Extras in case you pinch it)

Here is an idea of what you will be working with on the back of the engine. See your new best friend for the weekend? Screw located on the passenger side is visible and the other is catty-corner on the drivers side. You may also note the corrosive nature of the G-13 on the aluminum engine block.


You may see in the picture that the screw  is a T30 type. Some are an XZN, and it is rumored that it will be an M8. If you plan to do any serious work on your car, I can’t stress enough the importance of proper tools. This set is a life saver, the stubby style XZN socket set is genius, and has saved me on many occasions. Now more of a necessity rather than a convenience, are a good mini driver  and a remote hose clamp tool. I tried without the remote hose clamp tool, and I found it impossible. Just suck it up and purchase it.  If you have the XZN M8 screw, make sure your mini driver has an accommodation for it (I have a Kobalt one that comes with a lot of handy bits).

Ok, so off to the races. MAKE SURE THE ENGINE IS COOL! The only things I had to move to get access to the back of the engine were the snorkel for the air intake, the hose that goes to the vacuum pump, and the hoses from my 034 catch can to the pcv plate. So start off by removing those. I have seen people remove the coolant reservoir which seems completely unnecessary to me, but to each their own.


Close up of the vacuum pump fitting, which is an oettinger style clamp. Replace this with a hose clamp when reinstalling.


The vacuum hose to the firewall just pops out of its rubber grommet. Do this AFTER taking the nipple fitting off of the vacuum pump in the previous step. I emphasize this because if done out of order, you can break the plastic nipple on the vacuum pump.



If you break these pieces you will not be happy with the repair route. You will see why later, but remove the T30 torx bolts from the hard coolant line connection to the intake manifold and the front of the block. There is also an M8 bolt that holds the fuel line onto the hard coolant line so remove that too.



Put a drain pan under your car, around the backside of the engine where you will be working. Coolant is going to come out (maybe a quarter gallon).

Now, reach behind the engine from the passenger side standing by the fender, and use a pick to release the metal clip on the heater hose. This is a quick release clip, and does NOT need to be totally removed from the hose to allow it to disconnect. Pull the hose down towards the transmission tunnel and be wary that there is an o-ring in between the flange and the hose and some coolant will come out. This is where the optional o-rings come into play and I recommend replacing these. These are a couple dollars tops and take one possible leak out of the equation (Part # N90316802). Next, remove the electrical connector from the back of the coolant temperature sensor (this is done in the typical VAG way). Push down on the back of the L shaped clip and pull away. You can opt to remove the CTS now by removing the plastic retaining clip with the pick (pull it towards the firewall), and then just pop the CTS out. Another o-ring will be lurking in the connection.


I was able to remove the passenger side screw standing in the same location as the heater hose and CTS. Just snake your arm under the cam chain tensioner cover, and feel for the M8/T30 bolt on the passenger side with the right angle driver in your right hand. Guide the driver to be seated into the screw and back it out.

Once you have these removed, you can lay a towel or an old blanket on the engine and get comfortable. You will be here a while. Snake your right arm (with the right angle driver in your hand) behind the engine however is best for you. I went with kind of an under and up method. Now wiggle your left arm through the other way on the passenger side of the engine until you are bear hugging the engine. Feel with your right hand until you find the screw and use your left to guide it into place; apply pressure and loosen. Pop the flange out of the back of the block.

Okay, one of the harder parts out of the way. That wasn’t so bad right? Now look at all of those cuts and bruises on your arms, then at the tiny screws to show for it. But it still won’t come out yet. The worst part of the removal is upon you – removing the plastic welded coolant hose from the flange itself. This is where it gets tricky and the hose clamp remover really comes into its own. You need to blindly feel around from the driver side of the engine and find the clamp that holds the coolant hose onto the flange. Once you do that, guide the clamp removal tool onto the clamp, squeeze it and leave it. Work the hose clamp towards the driver side until it is just on coolant hose, release the clamp tool, and get it out of the way.

Lay down on the engine, grab the flange in your left hand and the hose you just removed the clamp from in your right. Start cursing and twisting the flange in your left hand while trying to pull the coolant hose towards the driver side. This is why you loosened the hard coolant line from the fuel line and block, allowing some wiggle room to pull it out. If you are having a lot of trouble, you can grab a pick and try to work it in between the flange and the rubber hose, but be careful not to tear it – just break the seal. Once you have this done, the worse is really over.

Now reverse this process completely. There isn’t really much to say about putting everything back together except a couple of tips.

  1. Be VERY VERY careful when you reseat the flange since the o-ring really wants to pinch (ask me how I know, I went through 3 o-rings trying to seat it and ending up pinching it). I lubed it up a bit with engine oil to get it to slip in easily (I also did that with the coolant hose hardline connection and heater hose).
  2. Don’t over tighten the flange bolts. Just generally be careful and pay attention to what you are doing. Stripping a bolt in the back of the engine would lead to headaches.
  3. Put the o-ring for the heater hose onto the flange first, and let it seat itself onto it. It will typically bunch and twist itself up if you try to put it in the hose and then seat it.

After you have it all together, top off the coolant and look for any leaks with your inspection mirror and a flashlight. If you have any leaks, you will have to take it all apart, inspect the gaskets/o-rings and repeat. I did this 2 or 3 times, so I feel your pain if you have a leak. Now start the car, and repeat the inspection. Let it run for a few minutes until the engine gets some temperature (maybe 1/4 mark), then turn the car off. SLOWLY undo the coolant reservoir cap until you get a pop and it sounds like air is bleeding out. Let it cool, and top off the coolant if it needs it. Take it around the block and let it get up to operating temperature. Be prepared to pull over and let it cool a bit though if it starts to overheat. If this happens, it is most likely just too much air in the system. Park at operating temp and blast your heat on HI with the fan all the way up. This forces the coolant to circulate through the system so it can travel to the heater core. Turn the car off, and repeat the slow reservoir air purge. Hopefully you are all done now with no leaks and a healthy cooling system once again. Grab a beer and relax, you are done! Well, until next time.