I am a big fan of Motive's power bleeder - happily used with adapters for my GM and VW vehicles.  So easy and efficient to push old fluid and air out of all four wheels quickly!

 

But there is no cap adapter available for the 1996 (not sure what other years) Legacy brake fluid reservoir.   The so-called universal adapter is a big pain.

 

So I took a trip to the junkyard to pick up an extra 3" cap.  I drilled out the center for a barb fitting and used large washers on each side to distribute the load on the silicon gaskets for the fitting.

 

I attempted to use the original gasket for the cap.  I cut out the center for the fitting.  But it would not seal at all.   

Turns out the original gasket is meant to use the center membrane - there is a small pressure relief groove on the edge of the gasket.  This prevents a true seal with the cap mod.

 

I tried several rigged "gasket-like" setups to try to get a good seal.  But it just wouldn't happen.

 

Then I realized that the three tabs under the gasket prevented anything from seating flat.   I ground these down flush with a Dremel and a craft knife.  Then I placed a toilet gasket (shown in the picture) that had an excellent bevel to it.   

 

Cap seals perfectly. - and now I can power bleed my Subaru!

 

Yep, I did the same thing years ago.   I love the ability to quickly bleed and flush the brake system.

I use Quick disconnect air fittings on my.  They seal fluid as well.

 

Nice Post.

GAAAHHHH!!!!
 

I did the same thing and it wouldn't seal either, thanks for describing that gasket issue, i never looked into that.  

In a previous life I would have cringed at using so much brake fluid.   But now I feel such a sense of satisfaction when the brake fluid flows clear and the reservoir looks like the day I bought the car new!

What kind of fitting went through the cap?

It's just a matching air fitting for the bleeder and a matching pipe thread fitting on the inside.