Rear brake issues

W

Weasellee

Member
Supporting Member
Joined
May 6, 2021
Messages
29
Location
PV,NY
The YJ has been sleeping for a couple years and I decided she needed to come out to play. In the 6 mile trip from storage to home the brakes were super soft til eventually they hit the floor.
Visually inspected all 4 corners to find no leaks but what looks to be a lot of stock parts.
After a good bleed nothing changed.
I went with my gut and replaced the brake master cylinder.
Much better pedal but still no rear brakes.
Gravel road brake test shows great front but no rear brakes at all
Open up the drums and the rear cylinders are not pushing out on both sides.
Now i replaced the two wheel cylinders and whilst there the spring kit.
Still no rear brakes. But solid pedal.

I’m thinking the soft line from frame to axle?

Ideas? Recommendations? Critiques on my methods?
 
Gilaguy23 said:
The soft lines can get swollen internally and cause issues. Sounds like your on the right track.
Click to expand...
Buying all three soft lines and replacing next. I think I’m going to buy the crown pre bent stainless kit and replace all lines. My daughter drives this rig. As long as nobody thinks it’s the booster then all the lines it is.
 
Those soft lines can be tricky , sometimes they swell up and other times they collapse so it traps pressure in the brake cylinder causing the brakes to drag and get hot.

If you're up the the challenge I can recommend the AGS Poly Armour brakeline tubing. It's easy to bend without kinking. All you'll need is the proper tubing flare tool for the ends. One coil of tubing is around $20 at your local friendly auto parts store. It's not a difficult job, just time consuming.

​

 
  • Like
Reactions: Weasellee
You said you bleed the brakes, I'm assuming the rear brakes bleed just fine?

I'm having similar issues so im curious what you find. I've replaced the caliper since one was iffy, but they bleed just fine. Still having issues.
 
JurassicJP60 said:
You said you bleed the brakes, I'm assuming the rear brakes bleed just fine?

I'm having similar issues so im curious what you find. I've replaced the caliper since one was iffy, but they bleed just fine. Still having issues.
Click to expand...
Fronts bled fine. Rears with new hard lines on the axle and new wheel cylinders still won’t give good pressure. I ordered Crown braided line set and when it arrives I’ll replace the rear soft line and in turn will need to replace the hard line from proportioning valve to rear of the frame.
I’m confident the issue I’m having is the rear soft line failure.

My fronts are fine. Hard stop on gravel fronts lock up rears no skid.

Make sure they f you have drums in rear you adjust them properly.

Air in the lines is usually the problem. Usually.

Let me know what you find.
 
This issue I solved with a phone call to Blaine at Black Magic Brakes. He sold me an inexpensive tool to install in the “proportioning valve “ where the dash brake light plugs in. This salved everything.
 
  • Like
Reactions: ytradio
solved
once bled, the valve will self centers, with a hard stomp on the brake pedal
then the brake fail lamp goes out. (did it?) /) was it on/?
you bought the bleed tool.

you never said the brake fail lamp glows

the tool just jams up this shuttle valve. (switch out)
the reset is just key on, and push hard the pedal and it self centers if not full of air or jammed.
after sitting for long years the valve corrodes inside and jams up.



proporting1.JPG
 
Last edited:
Dorf said:
solved
once bled, the valve will self center, with a hard stomp on the brake pedal
then the brake fail lamp goes out.
you bought the bleed tool.

you never said the brake fail lamp glows./
Click to expand...
It wasn’t glowing when i was bleeding because the key was off. 😁 Also wasn’t glowing when test driving. Hence the need for support.
 
I only posted for dead or super weak rear brakes. also 20% rear brakes is common, value for sure stopping fast on dry pavement.
the DOT3 fluid is hydroscopic and wants to rust all these parts out.
if lamp not glowing key on the lamp good means the valve is in the center. for sure.
the lamp can be tested easy , if suspected
jumper the black pin ground
and cluster lamp glows

here it is, see the 2 pins,
it really is 2 switches inside it not just 1.
the lift switch if for lamp direct
and the other pin sneaks (see the jump) in the parking brake switch.
so jumper ground pin G9 BK (means use the engine ground or battery neg or the body ground)
and the lamp glows, key on
then put back plug, G9/11
and if not glowing in cluster that all is good.
if glows all the time unplug the park brake switch first. key on.



tricky-brake-switch.JPG
 
Also wasn’t glowing when test driving. Hence the need for support.
its not suppose to.
you posted dead rear brakes (not skidding rears)

"Much better pedal but still no rear brakes.
Gravel road brake test shows great front but no rear brakes at all"
the rear cylinders reported dead
so air in the rear lines
or proportioning valve stuck inside.
i can stick at full on front brakes only if rears have air. that is what it does.
it will unstick if lucky , once all air is gone rear. for sure unsticks engine running and boosted assisted and driver hard braking the pedal.
if not the shuttle piston inside it is rusted up jammed (corrosion)
dismantle and clean it or buy a new valve.
is super old, and most that old are bad. for sure parked for years. now bad
 
Top Bottom