Coolant leak

[MR:OlympiaA4]

So when I first bought my A4 Quattro 3.0l it needed a lot of stuff since then and 4500 bucks later the coolant system was completely gone through new thermostat and expansion tank new coolant and new heater core, in addition to a lot of other not coolant system related parts. I was having no issues till a leak developed behind my engine by the rear firewall... in the past it was the thermostat O-ring that was leaking and the coolant was dripping off the back side of the engine due to the tilt of the engine, I checked the the upper intake manifold is dry the water pump is dry are there any hoses back there that could leak


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[Dodaman]

Sounds like the engine coolant flange. I have an 05 A4 with same motor. Others call this the rear coolant flange. I am having the same issue. A dried trail of pink and whitish crust coming off a fitting from the flange. I haven’t fixed it yet as I had to do my timing belt, water pump, etc. this weekend. From what ive seen and heard, it is a PITA as it is tight quarters back there. I may even get a quote from a shop. Not sure if I have the time to get it done. Let me see if can find my post about it. I was sent a few pics. I will be back shortly.

[Dodaman]

This is what I was sent by the member Gosser. He was very helpful. Good luck. Guess we can see who gets it fixed first 😀

On the diagram, it was #21 that was his issue as well as mine. Simple enough if it was easily reached.
I guess I should have said the one pic with the mess is once he cleared eaveything out, while the other is after he titghtened the small nut at that fitting. He pulled it and put Teflon tape on and it has been dry for the last 10,000km. Mine is the same set up. The flange itself isn’t leaking from the engine. It appears it is coming from the fitting unless the flange has a small crack in it. But that flange is metal, and I don’t want to swap it to a plastic one if not needed.

[pablolizarraga]

Here’s 2 other potential leak sources.

IMG_2473.JPG

IMG_2474.JPG

I just replaced the coupler on my coolant supply hose w/ this $5 URO coupler (3B0122291B).

IMG_2467.JPG

Inner diameter is a bit smaller but so far so good. To access, I just had to remove the breather tube from passenger side valve cover, disconnected some vacuum hoses above throttle body, and the plastic tube that connects to throttle body. You’ll have to push aside harness to get to that supply hose. Pull the metal clip and shimmy that coupler off. Be patient w/ removing coupler so as to not to damage the tube where it connects to; which I believe was plastic.

Good luck!


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[MR:OlympiaA4]

Thank you to all, I’ll investigate


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[Turbo510]

I had the rear-of-engine coolant leak, and it was a deteriorated/cracked coolant manifold, shown in red on the diagram above. About $120 for an OEM part, harder to change out than I had expected due to some tight clearances in a few places. Moving the fuel injector rail out of the way, and then removing the intake manifold, was the easy part. SAI pipes also have to be moved out of the way, and I had to disconnect the combi valves for the same reason. With all that effort, you'd think I would have replaced the O-rings, but they seemed perfect, and with a little Silicone sealant smeared on right before installation, I have had zero leaks for a couple of years now.

[jj94tt]

This is what I was sent by the member Gosser. He was very helpful. Good luck. Guess we can see who gets it fixed first 😀

On the diagram, it was #21 that was his issue as well as mine. Simple enough if it was easily reached.
I guess I should have said the one pic with the mess is once he cleared eaveything out, while the other is after he titghtened the small nut at that fitting. He pulled it and put Teflon tape on and it has been dry for the last 10,000km. Mine is the same set up. The flange itself isn’t leaking from the engine. It appears it is coming from the fitting unless the flange has a small crack in it. But that flange is metal, and I don’t want to swap it to a plastic one if not needed.

My issue was no.16 o-ring... though, don't let the forward position fool you... the valley fills up then runs over the rear of the engine around the trans bell housing.

[Gosser]

If you need that red highlighted pipe, let me know, I have a brand new one in a box still that I have no use for:
https://www.ecstuning.com/b-genuine-...pe/06c121085h/
will let it go for 70 bucks shipped.