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Brakes Puzzler

Dear Tom and Ray, & whomever–

My son owns a 1998 jeep cherokee. A little over a year ago he started having problems with the brakes seizing up. He was still under warranty from the brake job he had done at his local tire/brake shop, so we took it back to them. At that time, they weren’t able to truly diagnose the problem, but went ahead and completely redid the front brakes again, replacing the front calipers and pads, turning/replacing rotors as necessary. Now, 7000 miles (and about a year) later. He’s having the same problem. Again, the mechanic is having difficulty reproducing the problem. They took it out and drove it 5 miles with no problems and cannot figure out why the jeep is doing what it’s doing. We want them to really fix the problem this time and not just replace parts. Here’s the symptoms: The vehicle begins slightly pulling to the left without application of breaks. When breaks ARE applied, it pulls hard to the left. Eventually, subsequent to these symptoms, the brakes seize up entirely. If he give the brakes plenty of time to cool off, he can usually get it home or to the shop. He doesn’t drive this vehicle very much, and mostly short trips. Almost never engages the 4x4. Help!!

Correction from poster. Sorry, I meant to say, “When breaks ARE applied, it pulls hard to the RIGHT” (not left).

It’s possible the flexible line between the brake caliper and the metal brake line system near the front wheel is deteriorated inside and is at least partly clogged. The pressure of applying the brakes forces fluid through the narrow part, but the fluid can not easily return after pressure is released, so the caliper stays partly applied, and after a few cycles the caliper is locked. After waiting the pressure that built up leaks back through the clogged line.

When this happens in your chest, we call it a heart attack, and if you are lucky a surgeon can bypass the clogged artery. In a vehicle it’s a little easier.

I agree. The flexible rubber brake line is probably at fault. It will allow pressure to the caliper but won’t release it. This is very common and I really can’t see why a brake shop would not change it if you told them what was happening. Well…maybe I can. They got a brake job out of it.

This sounds like a wonderfully simple and rather inexpensive solution. However, I’ve also seen comments on other forums (on this site and others) that indicate it could be the ABS. My son’s shop has also indicated this could also be the problem. Is it easy to eliminate this as possibility? I would love to do that, as that could be much more expensive than replacing a hose. THANKS!!

Actually, the shop has been very good. Last year they replaced everything at no cost to us since it was under warranty. They are willing to fix it again this time under warranty, but are just having problems diagnosing the problem since they can’t get the vehicle to seize up when they drive it. I will pass this info along to them. I sure don’t want this to be an ABS issue. By the way, the shop is Les Schwab Tires. We’ve been doing business with them in one store or another for over thirty years and I have NO complaints.

I too would change the lines. especially since the braking is uneven.

However, since it begins to apply itself while driving and without pressing the pedal, let me suggest also looking at the brake booster. The booster is a vacuum diaphragm that uses the engine vacuum to assist you. Normally it has equal pressure applied to both sides of the diaphragm and is stable. When you push the pedal, it pushes a rod that goes through the booster canister and into the master cylinder. When the happens, the backside of the diaphragm is vented, the front side under vacuum, and that assists you. If the booster is defective or misadjusted, the vacuum could be slowly applying the brakes as you drive. If the booster problem is due to a sticking rod, that could also cause the brakes to not release properly when you take your foot off the pedal, manifesting itself as some of your other symptoms.

I’ve attached a link to an illlustration to help.

In my view you should stop worrying about the ABS and just have the shop replace the flexible hoses. While no job is free, this one is fairly straightforward and needs to be done anyway after 11 years.

There are other explanations, of course, but I’m a believer in doing one thing at a time,to see where the problem was. I am also a cheapskate, and so I try to come up with the simplest (cheapest) explanation.

Thanks gang! Again, I cannot say enough positive things about our own Oregon grown “Les Schwab Tires.” I talked to them this morning after this forum conversation, and it sounds like they are on top of it. They took it out for drive, but this time they had a heat sensor hooked up to the wheels so they could see where / when the heat is building up. Apparently, it told them enough that they are now on the same page as you all. Sounds like hoses, but they are going to go ahead and properly continue to diagnose the problem. The mechanic told me, “I’m not a believer in just replacing parts.” My confidence is restored!! If you are ever in Oregon, Washington, or Idaho, visit Les Schwab. They are a wonder to behold.

Tell your mechanics that any brake hose that has a steel bracket on it is subject to rust, which causes the steel bracket to swell, which squeezes and constricts the hoses, which causes just the kind of problems you are experiencing. Your Cherokee has these type of hoses on the front, so this is most likely your problem. It’s a shame you’ve been dealing with this for a year and the solution was right there in the form of a couple of $15 brake hoses.

Replace the cheap parts first… (the hoses). The ABS will have a fuse you can pull to disable it…