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Unread 08-24-2008, 08:07 PM   #1
battlecat
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having problems with front rotors heating on my 1988 Cherokee...need help!

for quite awhile I had some evidence of a warped front rotor, so I replaced both front rotors, used new pads and test-drove my Cherokee (1988). I drove only a few miles and when I got out, the front brakes were really HOT (burning smell) particularly the passenger side. I took her home installed a new passenger-side caliper/hose, bled the brakes, took her out for a drive...still hot (but not quite as hot). I talked it over with a guy who suggested I bleed all four brakes again (thinking the reason the rotors were hot was due to air in the rear lines, thereby putting too much emphasis on the front brakes to stop). I did this, but no change in the heating situation (there is not longer a super hot, smoking rotor...but they're so hot you can barely touch them for a split-second, even after a slow drive around town. I should note that both front rotors are heating this way (equally). This weekend, I removed everything, double checked the free motion of the pads, thoroughly cleaned, polished and lubed (with brake grease) the channels that the pads slide on, also filed smooth the insides of the notches on the pads. Still no improvement. When jacked up, (wheels off, calipers and pads installed) I can rotate the rotor (by hand) with some evidence of dragging pads, (but it's not too hard to turn the rotors). Now I'm wondering if the problem could be a malfunctioning valve in the master cylinder (not releasing pressure fully). When I crack the bleeder valves on the calipers, (to release some possible pressure), there is no detectable difference in the effort required to turn the rotor (and only a slight dribble of brake fluid...not a squirt... when I cracked the valve). Anyone have an idea what this could be? Are Cherokee rotors supposed to be that hot (nearly too hot to touch) after a drive???

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Unread 08-24-2008, 10:31 PM   #2
firefighter1c57
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I'm wondering if you got the correct rotors. Somewhere back in the eighties models the brake rotor depth changed. This was due to a change in the unit bearing. The depth wasn't much, but it would be enough to make the rotor drag the inside brake pad.
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Unread 08-24-2008, 11:51 PM   #3
bikedude189
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no. it sounds like they have perfect drag on them and that the calipers may be sticking a little. if you think that is the case, pump the pistons in and out a few times (make sure to not let it get all the way out *pop*!). or they may just be normal... unless its dragging excessively or they are hot enough to burn the boot on the tie rod end, then i think this is just normal heat....

after all a brake works by turning kinetic energy (movement) into thermal energy (heat) by means of friction...
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Unread 08-25-2008, 10:37 AM   #4
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I can think of two possibilities for your problem, first off....when checking your rear brakes did you happen to look for signs of a wheel cylinder leak or glazing inside the drums and are you sure the pads were adjusted out properly?

Secondly, if you're fairly new to the Renix model Cherokee it's only fair to warn you that the braking system totally SUCKS! If you were to drive any other type of newer/better brake design vehicle to the point of getting used to it then try driving a Renix Cherokee it'd be a miracle if you didn't hit something, the needed braking distance is probably 3-4X that of other similar weight vehicles. Basically, perhaps you're trying to stop in the same distance you have with other vehicles and are bearing down on the pedal to make that happen, which in turn is really heating up the brakes?

If none of the above is possible and everything on the axles checks out to appear "normal" I would start leaning towards master cylinder or booster issues as they were barely even adequate when new. The very first thing every other XJ owner would tell you to upgrade on the braking system is to switch out the stock master cylinder and booster for those on a 95-96 model as they are dual diaphragm (stock is single) and the rods are the same length so it's a direct swap for the most part. You can also swap out your rear drum set up for the rear disc setup on a ZJ Grand Cherokee to even further improve braking.

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Unread 08-25-2008, 10:59 AM   #5
tangofox007
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Quote:
Originally Posted by HeepToJeep View Post
I
Secondly, if you're fairly new to the Renix model Cherokee it's only fair to warn you that the braking system totally SUCKS!
The brakes on my '88 Cherokee work great. My TJ has front and rear disks and it doesn't stop noticably better than the XJ.

If your brakes don't operate properly, it might not be the fault of the "system."
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Unread 08-25-2008, 11:26 AM   #6
HeepToJeep
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Originally Posted by tangofox007 View Post
The brakes on my '88 Cherokee work great. My TJ has front and rear disks and it doesn't stop noticably better than the XJ.

If your brakes don't operate properly, it might not be the fault of the "system."
How do your XJ and TJ compare in weight? Does the TJ have a single diaphragm booster and are the rotors the same size as those on the stock XJ? The brakes on my 89 work well too and are of stock design but most vehicles of similar weight stop better. I've yet to hear/see anyone say that the master cylinder/booster or disc upgrade wasn't a pretty big improvement...have you?

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Unread 08-25-2008, 08:14 PM   #7
battlecat
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wow! Great ideas!

There are plenty of good suggestions to follow-up on here, guys! Your suggestions are much appreciated. Today, I decided to try another experiment (I drove the Jeep to work...20 miles one way, 65 mph).....this time, I pulled off the highway, let her coast to a near-stop (didn't touch the brake pedal) and stopped it with the emergency brake. Surprise! The rotors were not hot! But later, when I arrived at work (and had used the brakes normally), They were pretty hot again. So, apparently this is either normal heat...or the rear brakes are not supplying much stopping power...so I guess I'll have to check them out a little better (I installed brand new shoes about 2000 miles ago...adjusted them as needed) When I inspected all four brakes this weekend, I saw no evidence of leaking) I agree that the brakes have never been much to brag about, even at their best (I always used to wonder if I could ever lock 'em up if I ever had to...but I don't tend to drive like that). I am also gonna check out some of the other suggestions you guys made....thanks again!
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Unread 08-25-2008, 09:08 PM   #8
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It's normal for brakes to get hot after use. A friend of mine told me to splash water on the wheel and if it steamed, you have locking calipers or brakes overheating. One issue i had with my old TJ was bad bearings would cause the rotor to lean at a slight angle and rub against the pad at all times. This caused them to get real hot and also wore out the pads in a angled way.
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