absolutcq20v

I had the typical leaky plug while the car was running (I could watch bubbles come out from all around it)...
<img src="http://lh4.google.com/absolut27t/R68IXKCkovI/AAAAAAAABIQ/Y-EcB8avvEk/IMG_1463.jpg?imgmax=576">

...and this is what's under the o-ring sealed cap: a spring and a insert that bears on the inside of the cap...
<img src="http://lh5.google.com/absolut27t/R7uDsaCkrsI/AAAAAAAABiw/8TrrZhNi1VU/IMG_1546.jpg?imgmax=800">

<img src="http://lh3.google.com/absolut27t/R7uDs6CkrtI/AAAAAAAABi4/KcS2KuONrp0/IMG_1547.jpg?imgmax=800">

The o-ring I removed was an oddball size, in that the 3 dozen different sizes in the shop were close but not quite. So I looked into copper crush washers (for oil drain plugs) and found one that fit perfectly but was a little thin...the cap has a shoulder that bottomed out before the washer was engaged, resulting in a massive leak. Doubling up two washers worked perfectly and now it's as dry as a bone.

PS - I replaced mine after driving about 30 miles...which forced about half a quart of fluid out the opening when I removed the cap. When I first removed the cap the car had sat for a few days and not a drop came out. Just FYI.

BostonCQ

Mine is leaking in exactly the same way

cuatrokoop

I had mentioned that that is not a plug but the cylinder head and is spring-loaded to regulate pressure. Replace the copper crush washers with an o-ring to keep the tension correct on the spring, I'd do it sooner than later. Order the rebuild kit for under $6 from various online vendors. That way if another leaks you'll have every o-ring and seal you need...

quattro.pilot

i agree that crush washers are a better solution than the o-ring

cuatrokoop

o-ring part number.

You should be able to use the 026198049 rebuild kit that a worldpac vendor has for $5.21.

cuatrokoop

I disagree...

BernieBenz

Problem with the rebuild kit parts kit and my original O-ring size recommendation is that both were designed for the wrong interface seal surface under pressure. This O-ring under pump pressure must seal against the ID of bore in the pump housing, not the OD of the cylinder head. If the latter, the O-ring must be moved by pump pressure to seat against this bore ID, Not a good static seal design. Use a 2-019 rather than the previously recommended 2-018 generic o-ring.

Further, when installing the cylinder head with a new O-ring, the ring must be well greased, not just with PS fluid, to prevent differential area elongation and resultant localized cross section reduction because of the cylinder head rotation. This cylinder head need not be torqued beyond screwdriver tight to provide the required initial o-ring squeeze.

absolutcq20v

I thought of that, but the brakes performed as expected (in both passive and aggresive applications). I will keep it in mind, but the crush washers are working great as of now.

absolutcq20v

Take note of cuatrocoop's warning, though. I thought of the same thing during reassembly, but noticed no diff in brake performance. YMMV.

AudiSport4000

Id second Eric on this one.