Hello. I recently became the proud owner of a '90 240 sedan, 190/k miles. The brake petal went to the floor when I bought it. I bleed all four wheels and the petal came up to about 1/2 and would stop hard, but after two days it got spongy again and went to the floor.
Observations: I disconnected the brake lines at the m.c. and plugged the holes. Petal very hard pushing only 1". Both back wheels hard to bleed, using a pressure bleeder(20psi)nothing came out of nipple full open. Only by pressing brake petal was I able to get 3oz.fluid on more than 20 strokes. Front wheels bleed on pressure alone and rapid, but the brakes are tight on the front. Can't spin them with just the rotor, must have the wheels on, and even then they are hard to turn, but that isn't evedent when you are driving. One more thing, when the petal is spongy, it is possible to get a "good break" if you stomp the petal, but if you let up the least bit and then rebrake the petal goes to the floor.
Any advise where to look next?

The good news is I fixed the problem by installing a new master cylinder, the bad news is I wasted 3 hours bleeding and re-bleeding before I changed the MC.
I did the test where you disconnect the two brake lines at the master and plug the fittings. That test gave me a totally good petal, so I figured it was ok. Guess not! Does anybody have an idea why? jdl

I think you've got some contamination in your brake junction block, and/ or a master cylinder that is causing you your pedal grief.

try bleeding without the pressure bleeder. brake fluid should run out the bleed screws on its own .. if the back wheels dont bleed then start to think obstruction somewhere along the line. And i know this is sacrilegious in volvo land , but try bleeding all three bleeders (one at a time) up front drivers side, then all three bleeders (one at a time) up front passenger, then back to drivers side rear bleeder and accross to passenger side rear.
The dealerships around here use the gravity bleed. it works well for me after fussing trying to get a stiff pedal by pumping i could never get my pedal back until i gravity bled like the dealer recomended, i tried everything so i had nothing left to loose, Dont think master or break booster or hoses until you try gravity bleeding, i suppose you can always check your drivers side floor pan for brake fluid, but really give the above sequence and passive gravity bleed a try first.

oh yeah one more tip, you shouldnt need to fully open a bleed screw , it might just let more air back in . . 2 turns max ! some would say even less than that.

also , since you disconnected the lines from the master to plug them and check your master seals .. you could (if you have an assistant) gently crack the lines from the master cylinder (one at a time) with a paper towel under the connector, while your buddy pushes on the brake pedal have him tell you when he is getting to the bottom of his pedal stroke so you can close the connection before he releases. if you see air bubbles sqweezing out the threads of the coupler then repeat this until no more air. this summons new fluid from the resevoir and bleeds your master. if still having trouble, just write back. i'll offer up more suggestions. I've done soft pedal problems more than i care to admit.