I changed the seal on it and it totally stopped leaking. The gasket was less than a dollar and it took a bit to get it replaced. First you need to drain the contents and then remove and install. Once you get that done you need to bleed your entire system.

It worked for me and there is not a single drop coming out. There are two of them and I had a leak in the one closer to the front of the car.

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Audi TT