Brake Issues.

[cmcolfax]

Toss your thoughts out here:

1989 Chebby 1500 4.3

Brake fluid in Master Cylinder was dark brown and bubbled like percolating coffee when the pedal was pressed.

Replaced MC yesterday.

Bench bled MC before installing.

Bled brakes until clear fluid came out of all four corners.

Pedal still goes to floor.

Fluid in MC still bubbles when pedal is pressed, appears to have tiny air bubbles in it when I pull the cover.

Looks like it is sucking air from somewhere.

Fluid now leaks from front "hard line" on MC when pedal pressed.

Thoughts? Ideas?

I was gonna pull the MC, bench bleed it again and re-install tomorrow.

I got nothin...

-cmc-

[MACK]

pull the MC, bench bleed it again and re-install tomorrow.

-cmc-

You have major air somewhere. Re bleed everything. Make sure you use the tube and bottle method so you don't suck air back into the system.


http://media.popularmechanics.com/images/brake-bleed-a-0407.jpghttp://legacygarage.com/images/Pictures/Brakes/Bench%20Bleed%20master%20cylinder.JPG

[MACK]

Just reread the first post...did you check your brakes? You might have a bad wheel cylinder.


http://www.allpar.com/fix/pics/drum-brakes/Brake-Drum-BlownCyl.jpg

[cmcolfax]

You have major air somewhere. Re bleed everything. Make sure you use the tube and bottle method so you don't suck air back into the system.


http://media.popularmechanics.com/images/brake-bleed-a-0407.jpghttp://legacygarage.com/images/Pictures/Brakes/Bench%20Bleed%20master%20cylinder.JPG

I bled 'em using the "tube-n-bottle" method; but was rushing a little... Annie was was working the pedal and Brendan was starting to cry in his stroller while I was doing them.

Might replace one of the bleeder screws too, it was a different size and the hose I was using barely fit on the tip of the bleeder.


Just reread the first post...did you check your brakes? You might have a bad wheel cylinder.


http://www.allpar.com/fix/pics/drum-brakes/Brake-Drum-BlownCyl.jpg

DS rear wheel cylinder was a little wet. I guess I should just pick up a set of wheel cyl's and put them in.

Then deal with the hard line leak up front.

Was hoping to have this thing on the road by Tuesday... and I promised the wife I would not spend Monday working on it.

Oh well...

-cmc-

[TJRobbie00]

well.... i wouldn't drive till it fixed trust me on this one...
:blowup:

[cmcolfax]

Half a day's work...

One trip to Advance...

One trip to CAP...

About 12 beers...

And I'd say it's 80% fixed.

Both rear wheel cyl's replaced.

Left rear brake was fawked. Missing pieces-n-parts, etc.
Ended up replacing all the hardware, springs, clips, etc...

Replaced the leaking hard line at the MC.

Re-bled everything, including a "dump valve" on the ABS system.

Get a nice firm pedal until I start the motor.

Once the vaccuum comes up, I get a soft pedal and still get "burbling" in the MC.

Further investigation revealed air being pushed in to the MC from the booster diaphragm.

And closer inspection revealed the front of the booster housing moving nearly 1/2" when the pedal is applied.

Pretty sure the booster is shot.

Shoulda grabbed one at CAP when we were there.

Looks like a CAR run tomorrow to pirate one of the complete 4.3L Jeff saw there earlier in the week.

Hmmph.

-cmc-

Moved here.

[cmcolfax]

look into why its moving .BUT to test the power booster . apply the brakes & hold the pedal down . THEN Start the truck . If the pedal moves down a little bit the power booster is working .

Easy enough...



Bad dump valve. Take it out of the equation permanently.

'Splain me...

From some friends on the New England 'wheeling board....

-cmc-

[cmcolfax]

Booster replaced.

Six more beers.

Still get a good firm pedal with the engine off.

Goes soft as soon as I start it.

Jeff is thinking sticky front caliper.

I dunno.

I'm gonna run to CAR on Wednesday AM and grab the "isolation dump valve" from the same truck Jeff pulled the booster from and swap that in.

If that doesn't work then I'll try just bypassing it altogether... hooking the hard line that comes out of it directly to the prop valve / distribution block.

The saga continues...

-cmc-

More movage.

[cmcolfax]

Pics.

The "RWAL Isolation Dump Valve" is the rusty looking part directly underneath the MC and to the left of the proportioning valve / distribution block.

And no, that's not brake fluid splattered all over everything, it's ZEP Teflon Spray Lube I sprayed on the hood hinges.

http://forum.neow.net/index.php?act=attach&type=post&id=21489

http://forum.neow.net/index.php?act=attach&type=post&id=21490

http://forum.neow.net/index.php?act=attach&type=post&id=21491

From the looks of it (rusty and the yellow paint on the end), it looks to already be a JY replacement.

-cmc-

[cmcolfax]

Removed.

Actually did it on Wednesday, but had to work yesterday.

Still dunno if it solved the problem 'cause I have not had the time to bleed them yet.

The shiny new hard line runs from the rear of the distribution block to the hard line that runs all the way to the rear axle.

http://forum.neow.net/index.php?act=attach&type=post&id=21533

http://forum.neow.net/index.php?act=attach&type=post&id=21534

http://forum.neow.net/index.php?act=attach&type=post&id=21535

I will no longer have ABS, but that is no biggie...

I work again tomorrow, but hope to get them bled Sunday AM.

And go from there.

-cmc-

[cmcolfax]

:bump:

Well...

Re-bled AGAIN today.

Got air from all four bleeders.

No leaks at any of my new lines or fittings (I cleaned everything and everything around them with Brakleen and rags after I put it together).

No obvious leaks from the hard lines along the frame.

Finally drove it this afternoon though.

(Had some other self-inflicted issues to resolve.)

Did the "stomp on the brakes in Reverse" trick a coupla times and got the rears to adjust and seat in.

They lock up good now (remember, I bypassed the ABS system).

Pedal still feels soft.

Brakes work, but the pedal is soft.

You can feel them grab and the truck nose dive and start to slow as soon as you hit them, but the pedal still feels soft to me.

I am thinking there is still air in there somewhere.

And everytime I bleed them I am rushing for some reason or another...

-cmc-

[Ace4wd]

:bump:

Well...

Re-bled AGAIN today.

Got air from all four bleeders.

No leaks at any of my new lines or fittings (I cleaned everything and everything around them with Brakleen and rags after I put it together).

No obvious leaks from the hard lines along the frame.

Finally drove it this afternoon though.

(Had some other self-inflicted issues to resolve.)

Did the "stomp on the brakes in Reverse" trick a coupla times and got the rears to adjust and seat in.

They lock up good now (remember, I bypassed the ABS system).

Pedal still feels soft.

Brakes work, but the pedal is soft.

You can feel them grab and the truck nose dive and start to slow as soon as you hit them, but the pedal still feels soft to me.

I am thinking there is still air in there somewhere.

And everytime I bleed them I am rushing for some reason or another...

-cmc-

So what your telling us is the pedal still feels soft ?