I took a break from the transmission to pressure test the OEM coolant reservoir.  I plan to redesign this and make something from aluminum, so I needed to know what pressure the stock cap opened.

Some supplies: 1/8- and 1/4-NPT taps, with tap drills and Schrader valves.

I turned a plug for the OEM coolant hose, with a 1/8-NPT tap in the bottom.

It looks like the stock cap releases pressure right around 20psi.

I also turned this piece, a 1" sanding pad for my Matco mini-DA sander.

M6 thread.  It wasn't done in this photo, I had to machine a step in this side for clearance.

sand sand sand!