I have had a coolant leak that I can not find for about the past 2 weeks. Its a 2003 A4 1.8t Quattro by the way. I have taken the car to 2 different reapir shops to have it pressue tested and they cannot find anything. From everything that I was reading on here, it looks like the most likely issue is with the coolant flange. I was just wondering if this is right because the coolant does not leak when the car is running/hot. Only after it is cooled down. Just wanting to make sure before I dive into this fix. Thanks for the help.

 

Where do you see the coolant leaking? Is it on the passenger side leaking on the exhaust then it is likely coolant flange or hoses connected to flange.

 

The leak is a little off center towards the passenger side near the rear of the engine. All the signs seem to point to the flange being the problem.

 

I just had the same problem. I couldn't located ether but i run different tests to see what was happening. What i came up was that i drove the car around when it was hot and had pressure in the system, i lift it up in the ramps and open the coolant cap and right way your will get the pressure come out with the coolant and found the the spot where it was coming from which was the Thermostat.. Look at DIY http://www.audiworld.com/tech/eng.html maybe this could help you out.

 

Seems to be the flange by where you described the leak. Changing flange is DIY. Hardest part is getting all the hoses on top rear of engine out of the way to get to the flange. Did this 4 months ago and wasn't too bad. Make sure O-ring is seated properly on new flange when reconnecting and you should have no leaks.

 

If I can find the part here locally, Louisville,KY, then I am going to buy it and change it tomorrow. If I have to order it online it will be a few days. Either way I'll update tomorrow with where I stand on it. Thanks for the responses so far.

 

I was able to get the part from the local Audi dealer for $32. When I went to start the replacement I had a loose clamp, so I tightend that. Coolant leak almost stopped, but is still present. So I will be changing the flange in the next few days and will update when I am done.

 

Did this job today on our 04' a4 1.8tq at 116k miles. Total job was around 7 hours start to finish. It's absolutely hilarious how much crap Audi attached to that flange, I mean come on, just put it somewhere less retarded, damn. I hope this flange lasts another 116k!

One thing that got me was one of the small .25" diameter hard evap lines that attaches to the upper flange bolt. You really have to disconnect that evap where it meets the first rubber hose near the intake manifold. I wasn't able to remove the upper flange bolt until I did this.

I also completely removed the pancake valve which helped immensely to get my hands and tools back there. The hoses that connect the pancake valve were one there for the past 7 years and were a bit tough to get out. A right angled pick that can chase underneath the hoses helped. This goes for all of the stubborn hoses.

One thing I did differently was to connect the temp sensor, lower heater hose and the short 90deg hose to the flange outside of the car. I took this approach after reading how difficult it can be to get it on the flange in the car. I also could see no way in hell to get the clamps off of the short 90' hose connecting the flange to the lower coolant hard pipe. These are normal squeeze to release clamps, with a twist, they're German and require forged pliers blessed by the Pope to make them release.

I also had no idea the upper heater hose has a bleed hole in it. This really helps to bleed much better than the bleed screw on the hard pipe above the intake manifold.

Other than those notes, the diy's were great. Any DIY for this flange job should include one last step, a massage. Leaning over the engine bay for hours is not treating me well.

Cheers

 

can anyone post more pictures please. i been trying to do this all last day still couldnt take off the flange and the sensor off the flange. thanks

 

I think I might have this problem but unless it is running off some mother stuff before it hits the ground it looks like its coming from more to the side of the engine but I can see a little gunk in the back by my flange so I don't know if it is the flange or something more forward of the engine on the passenger side. Any help appreciated!