Front brake problems..

[RINGKONG]

1988 Cherokee Larado AW4 NP241 Dana44 rear.


I bought this truck last week for 1200 bucks, I bought the body and knew it had some mechanical problems.. well now I am trying to fix the brakes, the front ones will drag.

I have replaced the master cylinder, and both calipers and pads.

the previous owner must have attempted to fix this and other things and now I am trying to fix them CORRECTLY..

the brake pedal can pivot all the way to the bottom of the dash and sits up well above the accelarator pedal. I know this is not right and might be contributing to my front brakes locking up.

I looked under the dash and saw this part.. what is it and how do I adjust it? it was screwed ALL the way back(towards dash away from firewall) and bent over to the side, the brake lever would not contact the switch at all. plus it had a vacum line attached to it.

I have a feeling my booster is gone... but maybe not. How do I adjust the rod, maybe my master cyclinder is not disengauging all the way.. when I took the old master cyclinder out, the rod could be removed from the brake booster, is it supposed to do this? I don't remember my f150 booster to be like this.

here is a pic of the pedal height. it seem WAY to high..


sorry about the size... didn't have time to shrink it.

any tips,pointer, or help would be greatly apprciated.

thank you

 

[AZ Jeff]

The item in your first picture is your brake light switch. It mounts thru a hole in the bracket that supports the brake pedal. It uses a small spring clip type nut to attach it via it's threads. It must be adjusted so the pedal turns the lights off when at full release point.

There is probably a spec for adjusting the pushrod on the power booster, but lacking an FSM, here is a backup method:

1. Measure the distance from the mounting surface of the master cyl. flange to the cup on the rear piston.
2. Adjust pushrod on brake booster so rod protrudes from booster to same dimension as #1 above, plus about 1/10 of an inch.
3. This should place rod in slight pressure contact with rear piston when master cyl. is installed.

If you are not sure about the booster and it's condition, start by taking the booster to the local parts shop, and comparing it to a known good (new or rebuilt) booster for that year. If it does not look the same, suspect a funky booster, and replace with new unit.

If it DOES look the same, there is only one test for a bad booster: with system all bolted together, and properly bled, and engine OFF, pump pedal until it's ROCK SOLID. Hold the pedal down firmly, and start the Jeep. If the booster is working correctly, the pedal will drop some more as the vacuum comes up on the engine. If it does NOT do this, it's new booster time.

Hope this helps...........

 

[Matthew Currie]

I believe actually that if the thing has a vacuum line attached it is the brake switch for the cruise control. The switches for both the brake light and the torque converter unlock are separate and electrical only.

 

[RINGKONG]

The item in your first picture is your brake light switch. It mounts thru a hole in the bracket that supports the brake pedal. It uses a small spring clip type nut to attach it via it's threads. It must be adjusted so the pedal turns the lights off when at full release point.

There is probably a spec for adjusting the pushrod on the power booster, but lacking an FSM, here is a backup method:

1. Measure the distance from the mounting surface of the master cyl. flange to the cup on the rear piston.
2. Adjust pushrod on brake booster so rod protrudes from booster to same dimension as #1 above, plus about 1/10 of an inch.
3. This should place rod in slight pressure contact with rear piston when master cyl. is installed.

If you are not sure about the booster and it's condition, start by taking the booster to the local parts shop, and comparing it to a known good (new or rebuilt) booster for that year. If it does not look the same, suspect a funky booster, and replace with new unit.

If it DOES look the same, there is only one test for a bad booster: with system all bolted together, and properly bled, and engine OFF, pump pedal until it's ROCK SOLID. Hold the pedal down firmly, and start the Jeep. If the booster is working correctly, the pedal will drop some more as the vacuum comes up on the engine. If it does NOT do this, it's new booster time.

Hope this helps...........

thanks for the procedure... but how do you adjust? does the rod screw in and out like on a ford booster? or do I do some thing else? when I replaced the master cyclinder I could pull the rod completely out of the booster.. which I don't think is right....

thanks.

 

[RINGKONG]

I believe actually that if the thing has a vacuum line attached it is the brake switch for the cruise control. The switches for both the brake light and the torque converter unlock are separate and electrical only.

thanks, that makes sense.

Now where is the switch for the torque converter?

I have other issues with that...

 

[Matthew Currie]

I don't have one here to look at, but seem to recall that my 87 had a pair of switches, each with two terminals, that looked about alike, somewhere on the upper part of the brake pedal lever itself - that is, the switches moved with the pedal. This was a perpetual problem because if the wires weren't routed just right, one would pull off. One was for the brake lights and the other, I assumed, was for the TC. I notice on the 93 and 95 that there is now just one big plastic switch with many leads, attached to the bracket, where I believe the cruise switch on the 87 was, but I don't know when that change was made. I just looked at an 89 wiring diagram and there is something identified as the "cruise/trans switch" there, so if that is the case, it's quite possible that the switch with the vacuum connection is also used for the tranny! In the 95 FSM it's clear that all functions - cruise, TCM and stop lights - are handled by the one switch. But this is a big black one with many leads, definitely not like your two-lead white one.

You may have to do some detective work with ohmmeter or test lights to see what switch is supposed to switch what, and whether they're even still there. If the previous owner really messed with the system, it's possible they're just missing.

Anyway, there should be a hole in the upper aft part of the brake pedal bracket (just above the pink wire loop in your picture) into which that cruise switch should fit, and once the pedal itself is set right, it should be easy enough to adjust.

 

[RINGKONG]

I don't have one here to look at, but seem to recall that my 87 had a pair of switches, each with two terminals, that looked about alike, somewhere on the upper part of the brake pedal lever itself - that is, the switches moved with the pedal. This was a perpetual problem because if the wires weren't routed just right, one would pull off. One was for the brake lights and the other, I assumed, was for the TC. I notice on the 93 and 95 that there is now just one big plastic switch with many leads, attached to the bracket, where I believe the cruise switch on the 87 was, but I don't know when that change was made. I just looked at an 89 wiring diagram and there is something identified as the "cruise/trans switch" there, so if that is the case, it's quite possible that the switch with the vacuum connection is also used for the tranny! In the 95 FSM it's clear that all functions - cruise, TCM and stop lights - are handled by the one switch. But this is a big black one with many leads, definitely not like your two-lead white one.

You may have to do some detective work with ohmmeter or test lights to see what switch is supposed to switch what, and whether they're even still there. If the previous owner really messed with the system, it's possible they're just missing.

Anyway, there should be a hole in the upper aft part of the brake pedal bracket (just above the pink wire loop in your picture) into which that cruise switch should fit, and once the pedal itself is set right, it should be easy enough to adjust.

thanks alot for all your help. I will look into it.