2nd Gen Non-Engine/Transmission Front Disc Brakes Releasing

[tjm]

Hi all



I hope someone can help. I searched the entire forum no one else seems to be having this problem. When applying maximum pressure to the brake pedal the front brakes will grab then release, grab again, release again, then I'll stop. During the "release" phase there is a loud almost clunking noise like you can actually hear the calipers getting hammered or something. If I apply a moderate amount of pressure and increase my braking distance I dont experience the adrenaline rush.



I though it was the ceramix brake pads so I replaced with performance friction carbon/metal. That didnt fix it. I have brand new rotors on as well. Calipers are relatively new also.



My rear wheel ABS system isnt working or is out of adjustment could that effect the front disc brakes? I plan on converting to rear disc when I get the time and money to do so.



Any ideas would be helpful.



Tim

 

[B.G. Smith]

If the rear ABS is out of commision, the brake light on the dash should be on. My guess is the ABS is causing the problem. See if you can disconnect the elect. connectors from the ABS module and see if that changes the situation? bg

 

[tjm]

Thanks bg



Brake warning lamp isnt on. I'll try the electrical disconnect and report back. Thanks!



Tim

 

[tjm]

Kudos to bg



Removed ABS connector and the problem went away. All four wheels lock up. So the ABS system is causing it. I'll start trouble-shooting the ABS now. Its odd that the rear wheel ABS system can effect the front disc brakes. Looking at the service manual the only point where the front and rear brakes come together is in the master cylinder reservoir and in the combination valve. Combination valve appears to be working. I can see the plunger move in and out when the brake pedal is depressed and released.



tjm

 

[fortunate1]

Brakes mushy, losing vacuum?

I spent some time reading a few of these brake threads, and decided to jump into one instead of starting another. It's not that load sensor problem; I've got a '95. The brake pedal can go all the way to the floor/stop. The ABS & BRAKE lights come on for a while when at a traffic light, but then they'll go out after about 15 - 20 seconds when I get going again.



The big shop manual has a troubleshooting procedure for checking the vacuum lines, the pump, and other things. But I wanted to know if anyone has had this kind of thing happen to them, and see if there is a shortcut to the ultimate culprit here. I do plan to do a full system bleed first. Might this be the same problem that tjm is having?

 

[tjm]

fortunate1

I had an intermittant brake/abs warning light when cold. Went away after engine warm-up. Here in texas it didnt really bother me a lot. I replaced the brake vacuum switch near the fuse box under the hood. It measures vacuum and will report an error via the lamps. It looks like a speaker with a hose attached to it. Wasnt very expensive.



tjm

 

[B.G. Smith]

Originally posted by tjm

Kudos to bg



Removed ABS connector and the problem went away. All four wheels lock up. So the ABS system is causing it. I'll start trouble-shooting the ABS now. Its odd that the rear wheel ABS system can effect the front disc brakes. Looking at the service manual the only point where the front and rear brakes come together is in the master cylinder reservoir and in the combination valve. Combination valve appears to be working. I can see the plunger move in and out when the brake pedal is depressed and released.



tjm

I think the reason the rear ABS affects the front is, it causes the brake pedal to fluctuate with your foot on it, it is modulating the fluid to the rears while causing you to put more pressure on the front????? bg

 

[B.G. Smith]

Re: Brakes mushy, losing vacuum?

Originally posted by fortunate1

I spent some time reading a few of these brake threads, and decided to jump into one instead of starting another. It's not that load sensor problem; I've got a '95. The brake pedal can go all the way to the floor/stop. The ABS & BRAKE lights come on for a while when at a traffic light, but then they'll go out after about 15 - 20 seconds when I get going again.



The big shop manual has a troubleshooting procedure for checking the vacuum lines, the pump, and other things. But I wanted to know if anyone has had this kind of thing happen to them, and see if there is a shortcut to the ultimate culprit here. I do plan to do a full system bleed first. Might this be the same problem that tjm is having?

From what you describe, I would guess that you have an internal leak/by-pass condition inside the master cylinder. The fact that the lights come on indicates that the combination valve is operating and resetting after you drive off. The pedal should not go that far down without a leak somewhere. bg

 

[tjm]

I think the reason the rear ABS affects the front is, it causes the brake pedal to fluctuate with your foot on it, it is modulating the fluid to the rears while causing you to put more pressure on the front????? bg

Interesting Hypothesis. However I have since determined that its the rear brakes that are giving way. I stuck my head out the window and heard the "clunking" sound travel from the rear to the front.



I've never had good working rear brakes. Drums/components have 177k miles on them. Im going to buy the rear disc conversion kit from http://www.tsmmfg.com/2682.htm and hopefully fix my rear brake problems! I'll report back in a month or so after I get it done. No time to do it right now. Thanks



Tim

 

[tjm]

conversion almost done

I bit the bullet and did the conversion. Only thing I'm missing now is the E-brake setup. Conversion was simple. There are many threads here describing howto's. After the install I tested it out in a parking lot. Slammed on the brakes numerous times. Vehicle stopped nicely. I did the same on wet pavement numerous times as well, ABS kicked in and I was able to steer while stopping. Loaded truck with a pallet of Quickrete concrete (2800 lbs). Slammed on the brakes in parking lot. Truck stopped nicely. Im having Control Cables inc htttp://www.controlcables.com make a custom driver side control cable for me. It needs to be a bit shorter with the discs. I'll get it next week, install on the wkend, sanp some photos of my e-brake setup and post here.



Prior to conversion I did buy extra:

Rear Wheel seals

Rear Bearings

Axle nut clips



You can always take the items back if you dont need them. And they sure are handy if you do need them.



tjm

 

[tjm]

Pictures of E-Brake mounting hardware

Attached are pictures of my hardware install. Basically welded on 1/2 of an axle U-Bolt. This allowed for adjustment of the e-cable at the mounting bracket on the U-bolt, thereby taking slack out of caliper spring.



Custom e-brake cable from Control Cables Inc 562-949-0455. Cost me around $40.



tjm