Hello guys.


Got an elusive problem that needs urgent attention.


Ill go through it chronologically so you guys can get the picture.


93 Pickup. 22RE 5 speed.


1) I was wheeling in the rain 10 days ago. When I was exiting the trails, I noticed my brakes were spongy. Because it was a downpour, I figured the oceanic puddles I was crossing had saturated my brakes.


2) 6 days ago, I noticed my brakes had become exceptionally spongy. I figured that they just needed a good bleeding as I was a little low on fluid. Topped it off and during my walkaround, I found that a brake line entering the top of the 3-way T junction in the passenger side wheel well had rusted badly and a spray of brake fluid was erupting every time I applied the brakes.


3) 5 days ago I attempted a drive to and from work. On the drive home, my brakes failed entirely. Pedal sunk to the floor and would only lock the wheels up when fully depressed. (almost hit a school bus.)


4) 3 days ago I replaced the bad brake line. Upon screwing in the new fitting to the T junction, The line coming out of the rear part of the T was also rusted through and leaking. I replaced that line as well. both go up to the master cylinder along the firewall from that T junction. I inspected all other brake lines and they appear serviceable.
When I attempted to bleed the brake system after a job well done, I could not fully eradicate the air bubbles after 3 quarts of fluid. Brake pedal would hold, but sink to the floor under pressure. Master cylinder would make a "slurping" noise and the area directly under it on the brake booster was damp with brake fluid.


5) Installed a new master cylinder TODAY. Bled not only all four wheels in order, but the master cylinder itself and the LSPV bleed point. Even after bleeding all six points, and eradicating all air bubbles from the system, the brake pedal would only retain its stiffness with the ignition and engine off. After feeling good about how stiff the pedal was, I'd fire up for a test and the pedal would sink to the floor. Brakes would only engage with vigorous pumping, or lock up upon the pedal reaching the stop.


6) After head scratching and a beer with the old man, we tried a few strange theories. We disconnected the vacuum line from the brake booster. It made a sucking hiss upon breaking connection. When plugging the line with a thumb while disconnected, the brake pedal became stiff once more (though plugging with a bolt and a clamp for a braking test in the driveway resulted in.....wait for it....NO BRAKES) We tried a separate section of vacuum line and still, a very sloppy brake pedal.


Could this be the brake booster leaking air? The line holds its suction when disconnected, but upon connecting to the brake booster, the brakes do not work safely.


I need help and my dad and I have exhausted all conventional theories.


....and we're almost out of beer.

 

Not the booster....you have a leak sucking back air somewhere. Fix the leak and bleed the brakes.

 

Stupid question. You had the truck running while you bleed the breaks right?
Aside from that your calipers might be toast. If you has rust floating through the lines it could have damaged the calipers. If so try and replace all the lines and then new calipers. The calipers should have a core charge so take your old ones with you if possible to save a trip. I just had to replace the rear calipers on my 99 Chevy w/214k. So they can go bad.

 

What the hell would the truck running have ANYTHING to do with bleeding brakes?

 

Umm you have vacuums assisted breaks. The break booster needs to be functioning to properly bleed the breaks. Just saying...

 

No it doesn't....do you understand how the booster works?

Has NOTHING to do with bleeding the brakes. Whatsoever.

 

X2. All the brake jobs I've done that involved bleeding them was done engine off. You have power assisted brakes, they still work without vacuum just not the "power assisted" part.

 

So does anyone have any theories? Im thinking that booster is the weak link in the chain here since the pedal is sinking when the booster is connected.

 

I told you what is wrong. There is a leak that is sucking air back into your system somewhere.....either that or you are not bleeding them well enough. Did you bench bleed the new master?

 

Is your fluid level dropping? A bad booster will just act as is the engine is off, hard to depress the pedal.

 

Did not bench bleed. Bled the master in place. Fluid level is not dropping.

"Somewhere" is rather vague. I can surmise that myself. Of course it's leaking somewhere. That's why I'm asking on here man! Before I have to look everywhere to find that "somewhere", I'd like a few well-aimed ideas to keep my efforts focused and solve my problem soon.

When the engine is off, the pedal is very stiff and gives me the hope that the bleeding was effective. As soon as you turn the engine on, the pedal sinks under the weight of my foot to the floor.

 

Air in the master....or a bad master.

 

I was just wondering the same. I've never had a vehicle running while bleeding brakes.
??

 

I'll try a bench bleed and restart the process

 

I'm thinking if one line rusted through you might want to check the rest. Might be another line having issues. I think the T fitting in the passenger fender also feeds to the rear brakes. I'm betting you have air in the LSPV. Look at bleeding all brakes and lspv in correct order

 

I doubt the booster has anything to do with it. With the engine not running, you have "manual" brakes, and they feel stiff only because without the booster you can't push hard "enough" to engage the brakes. The booster only helps you "push" harder. (That's why you don't have the engine running to bleed brakes; to apply the brakes requires several 100 psi in the brake lines, but to bleed them requires almost nothing.)

"Pedal sinks to the floor" is not a sign of air in the system (air in the system gives you a "spongey" pedal). Instead, I suspect a bad master cylinder: you push the pedal to pressurize the lines, but instead of holding that pressure it's leaking internal to let the pedal drop. Of course, this all assumes you don't have a puddle of brake fluid accumulating on the floor.

Last, did I get your chronology right? You found that a "spray of brake fluid was erupting every time I applied the brakes", and then the next day you drove to work anyway? Find your Yellow Pages and look up "bus" and "taxi." Just sayin'

 

It was a discovery late Thursday night. I didn't notice anything more than a sponginess. Had to finish one last day of work before a weekend to start fixing it. Of course it wasn't good to do, but I didn't really have many options.

It is a brand new master cylinder. Im going to bench bleed the mc first, then the wheels. Where does the LSPV fall in on the bleed order? I was bleeding it between the rear wheels...but it was guessing.

 

You can bench bleed the MC on the truck by cracking the fittings. It has worked for me. Do the LSPV last after MC and all 4 wheels. Also check your drums are adjusted tight, it has a strong effect on pedal feel.

 

I would look at the lines you replaced .

All the connections need to be super clean the least little dirt in the Tee fitting can allow it to suck air with no fluid loss

As your brakes seemed to be working before the rusted lines leaked.

As long as your able to get fluid out of all the bleeders .

Remember it takes a long time to get your right front bled because of the lines to the LSPV

In all the Brakes I have ever done I never needed to bleed a New Master Cylinder.

Nor other then the my first very expensive bleeding of the LSPV have I ever touched them.

 

had something like that hapen when my rotors were so thin and the caliper pistons started leaking when the pads were too thin. how do the wheel cylinders look in the back, those can leak unseen.