Curing a soft brake pedal on a Jeep Cherokee
A soft brake pedal on a Jeep Cherokee can be very unnerving. The brakes are not exceptionally great on a Jeep Cherokee to begin with so when they are not working well, they can be downright scary.
The first place to look on a Cherokee is the adjustment of the rear drum brakes. If the shoes not adjusted right, then the pedal travel required to take up the slack will be enough to make the pedal feel soft.
To adjust the shoes, remove the rubber plug in the backing plate. Use a screwdriver or better yet a brake spoon to turn the spiked wheel. Turn it down to tighten the shoes. I usually tighten them until there is noticeable drag when turning the tire.
If the adjuster does not click when you turn the wheel, then the auto adjuster is likely not installed correctly. I see this problem often. The auto adjuster is operated by a cable the moves the adjuster wheel when the brakes are applied in reverse. The cable is routed over a small metal pivot point. Often the metal piece is not installed correctly under the spring and will allow slack in the cable. To fix, simply remove the spring and reposition the pivot plate in the hole and reinstall the spring. Just make sure the plate stays in place as you reattach the spring. That is the tricky part.
Also, if exposed to road salt, the adjuster screw may seize. Free it up with a rust dissolving oil like PB blaster or ATF. Coat it with grease when re installing to help prevent it seizing.
If the rear brakes are adjusted properly ands the pedal is still soft, you may have air in the lines or a leak. Check the rear wheel cylinders for evidence of leaks. Look for traces of fluid inside the brake drum. In the front, look for fluid around the calipers.
If you still have a soft pedal then you will need to bleed the brake system to purge any air. Air can get in if the master cylinder has ever run dry or if a brake line has been removed for any reason.
I prefer to use a pressure bleed system to bleed the brakes. I find it gets air out faster and I can do it without an assistant. I don’t like using vacuum bleeders because I have found that they can pull air in past aging wheel cylinder seals. If the seal are new this wont be a problem but old ones can allow in air during a vacuum bleed even if they don’t leak fluid out. The old “pump and bleed” method works if you have an assistant but is slower than a pressure bleed.
One last are to look at if you continue to have a soft pedal after checking all of the above is the front brake calipers themselves. Some Jeep calipers use a phenolic piston. The plastic in the piston can break down with heat and start to crumble. If the piston is breaking it may flake off a little each time the pedal is mashed.