'95 M3 - No fluid from any caliper when bleeding

[keyland]

Hey guys,

I made the mistake of trying to do some proactive maintenance on my 'new' M3 and get rid of the nasty black brake fluid that was in the reservoir.

We cracked open the bleeder screw on the right rear caliper and attached our vacuum bleeder which pulled about a 20 in-hg vacuum and held it without ever pulling any fluid.

Okay, well that's a little strange, so I open up the bleeders on the other calipers and again nothing comes out.

Switched to a pressure bleeder on the master cylinder at 20psi and still nothing comes out. Tank holds 20psi almost indefinitely.

Reservoir dry? Nope. Completely topped off and the level never changes.

Maybe the bleeder screws are rusted? Nope. Even taking them completely out yields no fluid.

Even when leaving the screws out completely for an hour no fluid comes out.

And, of course now with the bleeder screws closed the pedal goes straight to the floor and you can still turn the wheels by hand.

My current plan of action is to pull off the rubber lines and check for fluid there, but after that I'm completely stumped and out of ideas.

The brakes worked perfectly up to this point. Grabbed hard and had no sponge at all, but there was some pulsation.

Anybody have any thoughts?

[Yurick]

I had a similar problem once on my E30. It turned out that the caliper itself was clogged. It was inside the caliper past the bleeder screw thread. If you find this to be the case with you, then you will need to remove the caliper(s), then take out the pistons and clean the clogged hole from inside the caliper cylinder.
I did not want to take any chances and went ahead and rebuilt the caliper while I was already in there.