I violated one of my own rules and did some non-essential maintenance to my winter car in the winter. I'm paying the price.

The car is an '88 245DL automatic, non ABS. The original problem was the brakes required too much force on the pedal for too little braking, and the pedal travelled a little too far in the process. I felt this could be either the booster, unlikely, or the master cylinder. Pumped the pedal to bleed off the vacuum, held it, and started the car. Pedal dropped noticeably so I figured, master cylinder, and replaced it.

Bled the system with my home brew vacuum bleeder. Does about 10" max vacuum or the bottle collapses. Had a little trepidation going in because of a bad experience on my '80 Mercedes which clearly didn't appreciate the vacuum bleeding method. I've only used it to exchange fluid on the Volvos. Never had to actually replace a brake component so never had to actually "bleed" the system. A good run of luck with three 240's.

Followed Bentley's prescribed bleeding ritual; rear left, front left lower, etc. Everything looked cool, but the pedal had just slightly more than the ideal travel before firming up, no power, when I was finished. Torqued all the wheels on and rolled it out of the garage and about soiled my pants. Pedal sunk nearly to the floor under power, with alarmingly poor braking at best. Dropped it into drive and rolled it right back into the garage and almost through the workbench.

With no vacuum on the booster the pedal travels a good third of a stroke before encountering spongy firmness. Can't pump it up, or maybe just ever so slightly. We're talking 20 strokes and some imagination to say it pumped up a tiny bit, maybe.

Ok. Bled it the conventional way. Pump, pump, pump, prop the board against the seat, bleed, repeat; still following Bentley's. No diff.

Got the wife in the drivers seat (Hard of hearing. Mechanically challenged. Could have made money if I'd filmed it. Amazingly nobody had to sleep on the couch! She's an angel). She pumped and I bled. I jacked up the rear of the car so air could go up. I jacked up the front so it could go the other way (down?). We ran two+ quarts of DOT 4 through this thing. No diff.

Did some reading here on the forum and ordered the Motive pressure bleeder. Hooked it up, watched my brake reservoir bulge alarmingly at twenty PSI and ran another two quarts of DOT 4 through the system. Nope. Bulged that mutha out to 25 PSI, with my eyes bulging to match. Nope. Bulged and pumped, calmly, then wildly. No dice.

Did some more forum browsing. Dumped the Motive and rigged a bottle to each rear wheel, hoses in a couple inches of fluid. Stroked the pedals with the bleeders open and watched amazing quantities of fluid index through them at high velocity with nary a bubble. Did tops and bottoms of the fronts the same way. Waste of time.

At this point, it is impossible for me to believe there is one molecule of air in this brake system.

Rigged some plugs on the new master cylinder. Firm as you could ask, with and without power. If only it were connected to some brakes!

Ok. Examined all the calipers. Must have some lost motion somewhere. Replaced the rear left; one stuck piston. Bled everything. Same #&^%!! story! Ahhhh!!!

Maybe the wrong size bores in the master cylinder? Got one for ABS or something?

Folks, I ain't no neophyte. I've done ALL my own mechanical work for thirty years. The only thing I haven't tackled (yet) is rings and pinions. But this has got me baffled and humbled.

Help.

Chuck