Bobzombie

I was a tech for many years and have never paid anyone to fix anything of mine. I am very mechanicaly inclined however my 90 runner has got me baffeled again!

Long story...

Fri- front brakes making noise needs pads and rotors. Installed, repacked bearings, ect ect. everything went fine. To remove the hub i choose to undo the brake line from the caliper instead of unbolting the tie rod bracket. No big deal just had to bleed the brakes afterwards. bleeding went fine.

Sat- perfect! good braking

Sun- hope in runner to go for a cruise. half way out of my neighbor hood front brakes stuck. I force it back to the house stopping for ten min intervals every few 100 feet to let cool down a little.
Left front caliper stuck (i also check right side but it was not stuck). Crack bleeder screw, compressed pistons(pistons moved freely). I bleed down caliper and notice that there seems to be no pressure building and pistons are not moving so I check right side ..same thing. so I am thinking master cyl.
and I crack the front feed line loose at the master and as I expected no fluid squirting. Buy new master bench bleed fluid squirting out of both ports. I bench test old master, fluid only out of rear port. It looks like problem found YAY!!!............ WRONG!! Put new master on and start the bleeding process(i have always been told farthest first). I get good press and fluid out of rears,
left front same problem a slight drip that never gains any pressure. Right front a little better.

So I continue to repeat the bleeding process and even went as fas as undoing both sides of the lines and blowing air through(just to make sure it wasnt debris) I got pressure out of fronts but only once and only the first press and hold cycle then back to no pressure and only a slight drip
So the brakes have been bleed since about 3:00am untill about 11:00pm
gone through a whole quart plus some
There are no fluid leaks anywhere everything is tight all lines are solid and not pinched or crushed?????

I am completly and utterly dumbfounded
please help me and keep me from burning her to the ground >:/

sorry for the super thread

TNRabbit

Where is the slight drip on the left front coming from??

Bobzombie

the drip is from the bleeder screw (while bleeding)

Bobzombie

where in Md are you?

Cyclopsblown34

If this has an "umbrella" valve like an old truck(both lines from Master cyl run to a block and then split), you might need to open the rear bleeders with the fronts closed and mash the pedal hard to center the valve. This usually only applied if you have total loss of brakes on one end or the other. Once the leak is fixed, open the bleeders at the opposite end from the initial failure and close the bleeders at the end where the failure was, stomp on the brakes and it centers the valve and restores balanced brakes. I've only run into this problem once and it was just like you're describing but on a 79 Chevy 1/2 ton.
Good luck
Chip.

Bobzombie

There is no proportioning valve on this vehicle, it has two ports on the master one for the rear and one for the fronts. These lines go into a T and then to each side.
I check the T and it is not a valve,only an open passage way.

Cyclopsblown34

Have you changed your booster? How's the rod from the pedal to the booster? You got me grasping at straws something awful now.

Bobzombie

Havent replaced the booster because the booster does not contain the fluid. if the booster was bad it would only make the pedal difficult to push.the "push"rod looks perfectly fine, and the old master showed no signs of wear...

"You got me grasping at straws something awful now."
Tell me about it I am going crazy with this thing.

If there is air getting in somewhere then I should see fluid leaking out!?

Also even though there is no pressure (or should I say little) both calipers are clamping the pads when pedal is depressed and unclamp when pedal is let go.
Common sense tells me that there is air in the lines.But common sense also tells me that i should get some sort of pressure(either air or fluid) out of the bleeders when they are cracked open) and I should not have to bleed for hours. I need a vacuum pump to pull the fluid through the bleeder screws. If it doesnt pull the fluid through then there is a leak some where. Do you agree?

TNRabbit

I'm in Lusby, MD. A little over 100 miles south of you, right next to Solomon's Island.

Cyclopsblown34

How are you bleeding them, pump pump, hold bleed? I took a jar and drilled a hole in the top of it, put brake fluid in it about an inch deep, put a hose in the jar with the end submerged in the brake fluid and the other end on the bleeder screw after it is cracked open. I give the brakes several (10) pumps and then check the fluid in the jar and master cylinder. Top off master and drain off excess in jar. It helps to have someone watch the jar to see if it is bubbling.

Bobzombie

TNRabbit-Thats cool. I go camping/fishing/boating at solomans a lot of fun!!

Ok I think We might have figured it out. After speaking to one of the techs here and telling him the rediculous brake story he said he has seen the soft line colapse (which would explain the brake locking up,fluid has no where to go so it holds the pistons out) and the only time i got a pressureized bleed off on the left front(the one that locked) was after i disconected both sides of that line and blew compressed air threw.(which would have pushed open the colapsed section) then after the fluid pressure was applied the line collapsed again.

what do you think of this theory!?!?!?

TNRabbit

It's possible. never seen that one before.

Cyclopsblown34

I had it happen on a 92 Bonneville on the driver side. The car was barely a year old. The hose "cover" was intact and the inner tube became delaminated from the outer and must have been a hole in the tube. It would hold pressure and lock the piston in the out position and it wouldn't let any more pressure through just like what you're having. The hose is a cheap fix too. I'd replace both sides to play it safe.

Bobzombie

Yeah it makes sense! I will update you guys tomorrow I am working on it when I get home. Thanks for all your input.

Cyclopsblown34

Good luck!

scope103

I had a different pickup with similar symptoms; turned out that the flexible line was blocked. (Mine was easy to diagnose; I couldn't push the calipers in, and pressing the brake pedal didn't make them move out.) You may have a flex line that is deteriorating, so that it will work for a while until a piece inside the line moves in the way. You might be able to check that by disconnecting the flex line, and pressing gently on the brake. If no fluid comes out, you found it.

Bobzombie

Yeah Thats what I was saying . However I replaced both flex lines and I still cant get fluid out of any bleeders. I put an old ac vacuum pump on the bleaders (pulling 25psi) and still cant get any fluid. Is it possible that there is that much debris in ALL of the lines that 25psi would not pull through?I think that is pretty unlikely but what the hell else could be going on.

Any other ideas???

I am about to park it in the and watch the show

scope103

If no fluid from the bleeders, I would say the next step is to disconnect the line from the caliper. Step on the brake pedal (gently!) Fluid out=bad caliper. No fluid=keep moving, and disconnect the flexline from the hardline. Eventually you'll get back to something that works. The last thing you disconnected is the bad part.

The way I say it makes it sound easy, but removing brake lines is anything but. Get a GOOD flarenut wrench (don't use the crap I use). Be prepared to wreck a hard line (it will be one of the good ones, donchakno). If you wreck a line, try to get find a line with the correct overall length that has the flare fittings arlready on it. (Autozone carries them, but you may have to try a few stores to find the exact length.) Bending brake line isn't tough with the right $13 tool, but putting on double-flare nuts takes more talent than I can muster.

And good luck!

Bobzombie

My hands are tired of brake fluid and my head hurts.
So I am down to this...

1) The reman master cyl is bad
2) debris in the line/lines
3) clogged calipers/wheel cyl
4) she doesnt want to sleep outside in the snow

Bobzombie

before i get of work to go work on it BUMP!!