Rear braking testing and possible problem

So I have the stock drums on the rear. I wanted to make sure my braking was good for trip I'm about to go on so I popped up the rear on stands and put my jeep in drive.

I pretty much have to push as hard as I can on the brake to get the rear to stop, and this is just in drive without accelerating. I figured this couldn't be right so I took apart the drums, cleaned really well and replaced the shoes which had cracks in them. I also adjusted the shoes, parking brake, and bled.

I tried again and it was only marginally better so I started to look for other possibilities. I popped off the hardline from the master cylinder to the proportioning valve and found that the one for the rear was %100 dry, as in not one spot of fluid coming out or around the hardline that I disconnected.

So I went ahead and replaced the master cylinder, bleed, adjusted, etc... Now overall it was a little better but it still feels like it takes way too much brake pedal to get the rear end to come to a stop. My ebrake seems to be good however, given that that's mechanical I'm assuming I must still have a problem with the hydraulics.

Does this warrant removing and cleaning the proportional valve or is there another possibility I'm missing?

Thanks!

For reference, this is my 98 xj with 8.25 truetrac rear and 33s.

that sounds right.

even with rear disk, mine is the same way.

every rig I have ever done this test with its the same thing.

the brake bias on our rigs is extremely front heavy, which is a good thing. too much rear brake is a bad thing.

whats more important is if your rig actually stops the way it should under actual driving conditions. a jackstand test can't tell you that, and the fact that you say your ebrake works tells me the shoes are stopping the drums, so as long as your pedal isn't soft or you cant stop under normal driving conditions I would say leave it alone.

On stands you should always be able to stop the rear, esp with the 8.25 9" brakes.

Try re-bleeding the back 2 lines. Next look at assembly, IIRC, smaller shoe goes towards front. Also check to make sure wheel cylinders are not froze.
I had the last one happen.

-Ron

rockclimber said:

that sounds right.

even with rear disk, mine is the same way.

every rig I have ever done this test with its the same thing.

the brake bias on our rigs is extremely front heavy, which is a good thing. too much rear brake is a bad thing.

whats more important is if your rig actually stops the way it should under actual driving conditions. a jackstand test can't tell you that, and the fact that you say your ebrake works tells me the shoes are stopping the drums, so as long as your pedal isn't soft or you cant stop under normal driving conditions I would say leave it alone.

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I wholeheartedly agree with this. Most of your braking is done with the front on ANY type of vehicle.

I know the brakes are bit underpowered.

But...
This part where I said this still worries me:
" I popped off the hardline from the master cylinder to the proportioning valve and found that the one for the rear was %100 dry, as in not one spot of fluid coming out or around the hardline that I disconnected."

Even though I did get fluid coming out when bleeding the brakes. I think that fluid was only coming from the proportioning valve front section.

Sounds like you need to bleed the rear brake circuit some more

souske said:

Sounds like you need to bleed the rear brake circuit some more

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And replace the wheel cylinders.

To finish off the thread. My proportioning valve was dirty and had a broken o-ring. I cleaned with detergent and water and replaced the o-ring then bleed everything. I tried removing the gromet to get more braking power in the rear and it worked, but my rears locked before my fronts so I put the gromet back in. Overall my rear drums are operating a lot better and my fronts lock before the rear.

I also solved my chainy or metal clinging / ringing sound when going over bumps. My jeep came used missing the spring on the strut or crossbar in the drum brakes. This was causing the strut to jump and rattle making a really annoying sound. I'm happy to have this figured out after 2 years.

Thanks everyone

Qban said:

To finish off the thread. My proportioning valve was dirty and had a broken o-ring. I cleaned with detergent and water and replaced the o-ring then bleed everything. I tried removing the gromet to get more braking power in the rear and it worked, but my rears locked before my fronts so I put the gromet back in. Overall my rear drums are operating a lot better and my fronts lock before the rear.

I also solved my chainy or metal clinging / ringing sound when going over bumps. My jeep came used missing the spring on the strut or crossbar in the drum brakes. This was causing the strut to jump and rattle making a really annoying sound. I'm happy to have this figured out after 2 years.

Thanks everyone

Click to expand...

I am happy you got it resolved. When I had drums in the rear they usually lock before the front on wet or icy roads. That was with all OEM parts. At one time I had a problem with one wheel not stopping only to find the wheel brake cylinder froze. A replacement cylinder fixed that.