Question about Brakes Grabbing after Rain

My 98 XJ has developed an interesting condition and I wanted to see if anyone else experiences this. After an 8 hour work day I often come out to my XJ after it sat in the rain all day. I notice the first 3 or 4 times I apply the brakes they seem to grab a lot more than usual. I am also getting a slight squeal during this time which I just attribute to brake dust or pads warming up against a cold rotor. The brake fluid is full and I have no leaks. It could probably stand to be flushed but I've seen much much worse. Is this something to be concerned about? The XJ stops just fine and it never feels like the brakes aren't releasing....been there with a 4runner and back brakes that locked up. I'm thinking that brake fluid being water soluable and all....maybe after a heavy period of rain I'm absorbing just a bit of moisture through some older brake fluid resulting in this sort of grabby feeling.....anyone have any thoughts? I'm replacing the front pads in a few weeks because they're down to about 25%.

Usually that's just light surface rust on the rotors wearing off. If you look at the rotors before moving it, you should see some light orangeish/reddish rust spots all over them, after stopping a few times it gets scrubbed clean. Water in the brake fluid would give the opposite feeling, after a few brake cycles it could heat up enough to boil and give you spongy brakes due to the vapor in the line (I think.)

I get the same thing, scared me the first few times it happened as I was leaving work also. Usually I do a few good stops in the parking lot and then everything is back to normal. I always assumed it was light rust on the rotors...

That makes perfect sense guys....thanks for the quick replies. I didn't think the rust would start on the rotors that quickly but it makes sense that the problem would be compounded after a period of rain versus never having this problem during the summer. Thanks again.

yeah, it got me at first too... got curious and looked. I know overnight is more than long enough, so I figured a full day at work would be too.

:cheers:

98NWCherokee said:

That makes perfect sense guys....thanks for the quick replies. I didn't think the rust would start on the rotors that quickly but it makes sense that the problem would be compounded after a period of rain versus never having this problem during the summer. Thanks again.

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If i wash my jeep ad go drive it an hour later it does the same thing, i think it forms as fast as it drys.

I was thinking more like the brake drums not the rotors. My drums do that after it rains.

I have found you can minimize this by adjusting the brakes really well. I'm not sure what proportion of this is "the brakes grab when they're unadjusted," versus "adjusted brakes scrub off the rust quicker," but it helps a great deal whatever the cause.

Me too!

Mine do it to, but not as bad after changing the rotors

Khary23 said:

Mine do it to, but not as bad after changing the rotors

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Oddly enough, I also found that on my 87, which had chronic rear grabbing and lockup, it improved when I replaced the warped front rotors. I never figured out that connection, but it was there.

i've had this on other cars, if everything else is good its def the slight build up of rust on the rotors.

I've also had this on my jeep w/ the rear brakes. one side in the back would always lock up like a hair trigger the first few times hitting the brakes after it sat overnight on a humid night, or after sitting for awhile when it was moist/raining. Turns out that the monkey that did the rear brake drums/shoes last used BOTH big shoes on one side (the locking side) and both smalls on the others. Once i redid the brakes, new shoes/drums/hardware/wheel cylinders blah blah and re adjusted... never a problem.

You should be able to tell if it's the front or rears grabbing. Most likely as mentioned before, its the drums that need better adjustment to help this. Mine did it for a year until I did the rear brakes.