Jump to content

Brake Pedal Went Soft.


Recommended Posts

Was coming off of the freeway exit ramp and was slowing down as I approached the light and my brake pedal went soft and hit the floor. The brakes will grab real hard when you bottom out the pedal.

 

I checked the brake fluid and it's full. I couldn't see any blown lines anywhere. I'm clueless. :huh???:

 

The pedal used to be kinda firm. It was almost almost as firm as the clutch, but not quite.

Link to comment
Share on other sites

Although it sounds like an internal failure of the master cylinder, if that were the case I would expect that both (a) the brakes would NOT hold on a hill, and (B) it would not have happened suddenly. It sounds more like a ruptured line to the rear wheels. When that happens, the pedal still provides braking by the front wheels, but the pedal drops almost to the floor.

 

If possible, jack up the rear axle (put it on jackstands if you have them), then run it in 2WD up to maybe 10 or 15 MPH and slam on the brakes. See if the rear wheels stop spinning.

Link to comment
Share on other sites

I got to thinking. When I pop the cover on the master cylinder, should both sides be full of fluid? One side is full and the other is just damp?

 

AAAAARG! I ASSumed the master fluid levels had been checked already. Note to self: DO NOT ASSUME ANYTHING! :doh:

Link to comment
Share on other sites

I got to thinking. When I pop the cover on the master cylinder, should both sides be full of fluid? One side is full and the other is just damp?

 

AAAAARG! I ASSumed the master fluid levels had been checked already. Note to self: DO NOT ASSUME ANYTHING! :doh:

 

Don, just an oversight... He did say he checked it... Don't beat yerself up.

 

 

I checked the brake fluid and it's full. I couldn't see any blown lines anywhere. I'm clueless. :huh???:

 

The pedal used to be kinda firm. It was almost almost as firm as the clutch, but not quite.

 

I think he's got it now...

Rob L.

Link to comment
Share on other sites

I got to thinking. When I pop the cover on the master cylinder, should both sides be full of fluid? One side is full and the other is just damp?

The big chamber feeds the front brakes, the little chamber feeds the back brakes.

 

Let me guess -- the little chamber is the one that's empty, right?

 

Look for a popped hard line across the rear axle, or somewhere in the area where the lines run along the frame next to the gas tank.

Link to comment
Share on other sites

I got to thinking. When I pop the cover on the master cylinder, should both sides be full of fluid? One side is full and the other is just damp?

 

AAAAARG! I ASSumed the master fluid levels had been checked already. Note to self: DO NOT ASSUME ANYTHING! :doh:

It had been. He reported that it was full. He didn't understand that the two chambers are for different ends of the truck.

 

I checked the brake fluid and it's full.
Link to comment
Share on other sites

I got to thinking. When I pop the cover on the master cylinder, should both sides be full of fluid? One side is full and the other is just damp?

 

AAAAARG! I ASSumed the master fluid levels had been checked already. Note to self: DO NOT ASSUME ANYTHING! :doh:

 

Don, just an oversight... He did say he checked it... Don't beat yerself up.

 

 

I checked the brake fluid and it's full. I couldn't see any blown lines anywhere. I'm clueless. :huh???:

 

The pedal used to be kinda firm. It was almost almost as firm as the clutch, but not quite.

 

I think he's got it now...

Rob L.

 

No love for me Don?

 

:dunno:

 

Rob L. :D

Link to comment
Share on other sites

Yep. Little chamber was empty.

 

Found a broken line just about where the lines go by the gas tank, that I couldn't see in the dark. Looks to be the only line that a po didn't replace, all of the others look new.

 

While I'm at it, does anyone have any info on the proportioning valve bypass? Like a good writeup?

Link to comment
Share on other sites

The two outlets on the front metering block (that thingie just below the master cylinder) that go to the rear are to forward two. The one that comes out the "nose" is the one you keep. The one out the forward bottom is the bypass, and that gets blocked off. Go to a good hardware store and buy a 5/8 SAE (fine thread) bolt. The shortest available is 1" -- cut it off to about 3/8" long, put an O-ring around it, put a dab of RTV on the end, and screw it into that front/bottom outlet.

 

Run ONE new line from the "nose" outlet in front directly to the flex hose at the rear axle.

 

Done.

Link to comment
Share on other sites

  • 2 weeks later...
The two outlets on the front metering block (that thingie just below the master cylinder) that go to the rear are to forward two. The one that comes out the "nose" is the one you keep. The one out the forward bottom is the bypass, and that gets blocked off. Go to a good hardware store and buy a 5/8 SAE (fine thread) bolt. The shortest available is 1" -- cut it off to about 3/8" long, put an O-ring around it, put a dab of RTV on the end, and screw it into that front/bottom outlet.

 

Run ONE new line from the "nose" outlet in front directly to the flex hose at the rear axle.

 

Done.

 

Got it all put back together, and running the new line from the block was a big pita. At least the stupid valve is gone.

 

O'Reilleys actually had a threaded plug that fit perfectly into the block. I didn't do an o-ring or any rtv, maybe I should have. I just opened the package and threaded the brass plug in.

Link to comment
Share on other sites

O'Reilleys actually had a threaded plug that fit perfectly into the block. I didn't do an o-ring or any rtv, maybe I should have. I just opened the package and threaded the brass plug in.

You should be good. Under normal conditions there's nothing coming out that port anyway, so no pressure that might force fluid around the threads of a dry plug.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...