Brakes act funny on rainy days?

for the three years that i've owned my Cherokee, the brakes have always acted strange on rainy days... the first time the brakes are used on a rainy day, a light tap on the pedal jerks the car to a stop. this usually reoccurs through the second and sometimes third stop, after which the brakes seem fine. lately, though, there is a new addition to the rainy day behavior - the brakes seem to slip and make a loud noise prior to the heavy lock/jerk. do any other jeep owners out there experience similar brake behavior??

This is not something I've run into and it looks like no one else has either.

Have to ask - are these shoes/pads what came new with the vehicle or have they been changed?? and can you tell if the front or the back brakes are the ones affected??

Grease will cause brake grab - could be a leaky rear wheel seal........

JD

are your rubber covers on? they are about 2" long inside bottom of rear drums, they pop off to allow shoe adjustment, maybe moisture getting inside? have you had to add brake fluid? sign of a leak...wheel cylinder.

You might be missing the slash shields for the rotors. These are the thin steel dinner plate-sized things that cover the inside of the rotors. They can rust away and let road spray cover one side of the rotor. Mind you, I have not had any on my Jeep for a year and there is no difference with my brakes, wet or dry.

" the first time the brakes are used on a rainy day, a light tap on the pedal jerks the car to a stop. "

I saw this same behavior on my '98. I never saw it escalate to what you are seeing though, and just considered it normal.

I share your pain... on rainy days, my brake rotors will rust a little and when I start out, it will actually lock up if i use a little force on the pedal. I have performance friction brakes, and it has actually helped somewhat considering that the pads are less vulnerable to the weather than the standard pads. the rear brakes will 'scrub' a little after a rainy day if I don't drive for a while.

I don't know why but this is very common on jeeps with drum brakes.I know if you change the shoes and cut the drums it will fix it but in time it will probably start doing it again

I've had it on a few drum-brake cars, but jeeps seem particularly prone. it usually doesn't happen until the shoes are over 50% worn.

what causes it (I'm no mechanic, but fixing this stopped the problem on mine) is the adjuster (opposite end of the shoe from the cylinder), doesn't adjust out.
after a while your shoes are only hitting on the top half of the drum. without even pressure they can bind. in the rain you have less traction so it binds easier.

the adjuster is supposed to extend one click when you hit the breaks in reverse(until it has all excess travel taken up). when the adjuster works the shoes push off of it on one end and the cylinder on the other. when it doesn't the adjuster end stays too narrow to reach the drum on breaking, so only the top (cylinder end) does the breaking. since you aren't putting even pressure on the drum and shoes it binds.

it has a sheet-metal lock that lets it ratchet out on reverse braking until you get the proper adjustment. the problem is when the adjuster either rusts tight or the sheet-metal keeper breaks and the adjuster stops adjusting.

you should be able to take the drums off and clean it out. replace the shoes if they are very uneven on the wear. check all of the retainers, and make sure all of the clips and springs are in good condition and in the right place.

if the adjuster is worn with severely rounded edges on the ratchet nut, or so rusted that it doesn't thread easily replace it. before reassembling coat the adjuster with a good grease, both on the threads and where it mounts to the shoes. (I used a synthetic gun grease, it coats well and doesn't wear off, without the need for any more than just a thin coat)

while you need to thoroughly coat the adjuster, obviously you want to be sure that you wipe off any excess and only use enough grease to get the job done. excess grease in the brakes can't be a good thing.

I hope this helps for you.

im havin the same problem with my 96 cherokee classic...after it rains and my jeep sits for a bit, the first bit of pressure on the pedal will jerk it to a stop, and sometimes even lock one of the wheels up until the pedal is released. im almost positive that it is the front brakes becasue i just replaced them about 400 miles ago, and after i did, it actually got worse. very disappointing. my slash shields are both good, so i cant figure out what it could be. i asked a mechanic that im good friends with, and he didnt look, but he said its just the design, the way the weather will get to the rotors and pads, which is odd if so few people have the same issue. if anyone figures this out do tell because this is extremely annoying...whenever i leave a parking lot after rain it looks like im standing on the brake pedal for no reason. what im trying is not releasing the pedal all the way after shifting out of park and using the gas to get rolling, and just riding the brake for 20 or so feet so the rust can wear off before i need to use the brakes.

for the three years that i've owned my Cherokee, the brakes have always acted strange on rainy days... the first time the brakes are used on a rainy day, a light tap on the pedal jerks the car to a stop. this usually reoccurs through the second and sometimes third stop, after which the brakes seem fine. lately, though, there is a new addition to the rainy day behavior - the brakes seem to slip and make a loud noise prior to the heavy lock/jerk. do any other jeep owners out there experience similar brake behavior??

Jack the car up in 2WD and see it the brakes work (in drive of course).
On my 97 with 124K on it...the wheel cylinders were not functioning or needed to freed up. I freed one and replaced the other....should have done both though. So the car was just stopping using the front discs.

You didn't say if you had ABS. There are things wriitten about that also.

I found out about my problem when doing a California smog test on the dyno....the rear brakes were not working to stop the dyno rollers. Surprise!! My daughter had complain about front lockup in the rain also.