Brake Troubleshooting

[DanHfmn]

So my brakes suck...

I swapped in an 8.25 last fall and they've been bad since.

Today I put the rear end on jackstands and put the jeep in gear, when I step on the brakes it doesn't seem to even phase the rear wheels, they just keep on spinning. The E-Brake does slow them down and stop them.

I've bled them to death, doesn't seem to help.

So my next step is the brake cylinders in the drum brake, good idea?

 

[joe_peters]

Just guessing but you might want to adjust the rear brake shoes. They should just drag the drum when adjusted right.

 

[DanHfmn]

I'll check that again, I've done that in the past too. Maybe that part isn't working properly and it's not staying adjusted.

Thanks!

 

[winterbeater]

When I tore mine apart this fall, I noticed that the little adjuster cable gizmo on one side was too long. It will never adjust the "star" wheel properly. It was late at night so I just put it back together. Most the other rear drums I had would adjust up by driving backwards and pumping the brakes, but obviously, due to lack of dimensional control of the parts, that doesn't always work.

Something bothers me though on the adjustment issue. You did not say that your pedal is going to the floor. Is it going to the floor? If so, can you pump it up and make it hold? Do you have antilock brakes?

 

[DanHfmn]

The pedal feels good and firm, there just doesn't seem to be good pressure at those rear wheels.

I replaced the free spinning side wheel cylinder, and it definetely helped. But even holding the brake pedal down, the rear wheels still creep and rotate a little.

The shoes and drums are probably pretty old/worn, could it be just a lack of good friction?

 

[winterbeater]

Not unless they are soaked in oil or brake fluid. You don't have antilock brakes?

 

[DanHfmn]

Well the original rear axle did, but it blew up so I put an 8.25 out of an early 90's back there to replace it.

 

[winterbeater]

If your replacement axle doesn't have the anti-lock sensors in it you probably need to bypass all that stuff. You haven't said your year, but maybe you should research putting in the Grand Cherokee junkyard booster/master cylinder with the dual diaphragm. I seriously doubt that bleeding or adjustment will fix your problems. That would only help if your pedal was now going to the floor. Your hydraulic pressure is being stopped up front before the wheel cylinders expand far enough out. Or else your pedal would bottom out.

 

[latenights]

proportional valve? just throwing it out there. my rear brakes didn't work either and it ended up being the proportional valve

 

[DanHfmn]

Yeah, I replaced one on a YJ a while back when I did an 8.8, I need to check this one out, good idea.

 

[mini=man]

I rebuilt my rear drums becasue I had no rear brakes due to a blown axle seal, but the new adjusters and springs never hurt. I think for both side it ended up being about $50 with shoes at AutoZone. Then I just had to adjust them. But in my experiance drums are constanly needing adjustments no matter how new the parts are. I now carry the adjuster tool in my center console for when I start to loose my park brake.

 

[winterbeater]

I agree. If bypassing the antilock shit (not easy, maybe just replace with non-antilock) doesn't work, add a proportioning valve. But I don't think it will work WITH the antilock.

 

[TiRod]

Just to recap what we've learned: You're running a non ABS back axle, with no sensors, hooked up to an ABS car, and the back brakes don't work.

Right, you have done exactly that - disabled the back brakes. The ABS is looking for rear sensor input.

Disable the ABS, you may need to add a proportioning valve, and when properly dialed in, you will have engineered the system back to normal. Or, add the sensors and tone rings, and the brakes will start working as part of the system.

Once you have the back brakes working as part of the system, then other mods like boosters, disc conversions, etc. come in. Welcome to the world of hot rodding, you are now the vehicle engineer, make your choices wisely.