Help, Stumped! 5KTQ Brakes

[Edward R. Wendell IV]

You're not losing fluid and the master cylinder is making pressure 
because it's new so I vote for the only other component in the brake 
system that can cause a lack of pressure to the calipers: ABS actuator.

The Bently manual has all sorts of leakage tests in it for the ABS 
actuator. You need a couple of pressure gauges in the 2,000 psi range 
plumbed into the brake lines on the input and output of the ABS 
actuator. I'm guessing that the engine off / engine on change is simply 
because you can generate more force on the master cylinder with the 
hydraulic assist running than you can with it off. You probably have a 
bad bomb which means that you don't have any hydraulic assist with the 
engine off. It's either that or some sort of logic in the ABS 
controller that only turns it on with the engine running.

Roy Wendell
Clarksburg WV USA
86, 87 5kcstq
87 MR2 times 2
Three turbos, two quattros, too much fun