Hi, been a while since I posted here.
Got family in town and...........
Having a sudden issue with brake pedal sponging to the floor. Dang!

(At least the main sewer line backed up twice already in a week so we are batting 1000. :-)

It was braking normally when pumping a few times, then it just acted like something was wrong pulling out of the driveway and brake light on dash came on.
(This used to go on when the switch would get stuck, btw)
Van had sat for a while. I had the brake master replaced a few years ago.
Seemed like a bad master.
So I replaced it today with a Napa Auto Parts new one. I bench bled it really good and then bled every brake RR-LR-RF-LF.
There was a lot of air in the back brakes, btw.

So this didn't do the trick.

When I push the pedal down when the engine is running there is an audible hiss. Seems like it has been doing that forever. Maybe this is not normal and the power booster finally gave out?
at the lower end of the pedal travel you can actually engage the brakes but the throw is only about an inch at that point and you really have to stand on it to get the van to stop. Locking up the brakes may not be possible now.
the ability to pump the brakes to get the pressure in the pedal hard has gone away.
And starting the car doesn't seem to alter the equilibrium of the pedal stiffness, but I should double check that.

I checked the 1 way valve on the booster. I am able to suck air through it. When "blowing" air through the valve from the end that attaches to the booster it does seal but it is not "perfect" air tight.

Also blowing into the tank when attaching a snug hose in the hole produces a balloony back pressure effect you would expect. Again, this is not a "perfect" seal and I imagine a pressure meter might find it reducing in pressure somewhat over say 20 seconds.
The vacuum hose is working and there is significant pull when the engine is running. Near the engine block where it makes a 90 degree turn there is a plastic valve - not sure what that does.
That said, Does it sound like a bad booster?
And since I have a lot of time into bleeding these brakes with the brand new master, can the booster be slid out from behind the master without disconnecting the lines?

Thanks guys for any help.

 

Sounds like you blew a brake line somewhere....... I would want to physically touch, and run my hand down all of the rear lines, and verify they are still good.

 

I opted to try a new (Cardone reman) booster today. Spent most of the day getting the old one out painfully trying to reach the nuts.

The new one acted worse and went to the floor even thought there was solid pressure with engine off.
I adjusted the pushrod to be further forward to mate with the piston without causing brake drag and no difference, just ppppft... to the floor with no resistance and less actual "stopping" clearance than the original booster.
So I was thinking maybe the original booster is not the issue? I put the old one back in. (PITA!!)

Maybe you are right about a bloated line somewhere. I dont see any leakage but have not had the wheels off.
Last year I had the rear wheel cylinders replaced.
Looks like I may have to pay the man to put her on the rack tomorrow. As every UPS man was dodging my feet today!!!
What would cause a brand new Brake Booster make the pedal hit the floor faster than an old one?

 

It works better, and gives you more assist. You have a hydraulic problem there somewhere.......

 

Ah, of course. Got it up on the rack with wheels off last night. Whole rear end was shot. Going to replace with all new USA parts and blow out the lines and start from there. Will keep you posted!

 

The van brakes work great now. While fiddling with the previous "to the floor" scenario, I noticed the "BRAKE" red light came on and stayed on. Can't figure out how to get it to go off. I seemed to remember in the past that pushing the brake pedal to the floor would reset it. But the pedal is firm now. There doesn't seem to be any hanging up of the parking brake switch either. I did have a temporary issue with the #7 25amp fuse blowing and my Right turn signals (front and back) were out. BTW it that fuse supposed to be hot even when the key is off? Test light shows it has voltage from one metal clip to the other.....

 

If the brake lite is still on, need to find out why.

One trick I like to try is: Grab a friend, stick 'em in the drivers seat. Have them pump up the brakes, and HOLD pressure on them, while you crack open a rear bleeder. Do that a couple times on one end, (use the same bleeder) then pump 'em up, see if the lite goes off. If not, do the same thing with one of the front bleeders. Should reset the lite.

 

most likely proportioning valve has pressure differential.
If bleeding does not equalize the pressure on both sides of valve then try this.

Reset the Proportioning Valve: A brake system proportioning valve is designed to monitor the front and rear brake pressure. When a difference in pressure is detected it will trigger this valve which in turn turns the brake warning light on. If repairs have been made and the light is still on the valve must be reset by pushing hard and quickly on the brake pedal. This action should push the proportioning valve plunger to the center of the valve and turn off the warning light.