How front brake caliper slides?

Tiny
MCJEEPIN
  • 2002 JEEP WRANGLER
  • 107 MILES

How do you get the front brake caliper guide/sliding pins on a Jeep TJ to slide freely and not stick every time they sit for a couple minutes!

P.S I'm using brand new pins, sleeves/boots, and grease.

I have tried different amounts of grease.
I have tried putting the pins inside the boots OUT of the caliper mount hole to see if the caliper mount hole was too tight and nothing changed. STILL STICKING!

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Friday, June 22nd, 2012 AT 12:38 AM

25 Replies

Tiny
RACEFAN966
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Have you used the ceramic caliper lube? If not try that its the heat that boils out other greases. Also the sliding area is there any grooves in it?

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Friday, June 22nd, 2012 AT 12:46 AM
Tiny
MCJEEPIN
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There are little ridges inside the rubber boot piece and the metal pin that goes inside the rubber piece is smooth and brand new.

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Friday, June 22nd, 2012 AT 1:21 AM
Tiny
RACEFAN966
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Emery cloth the ridges a little to smooth them and then use the ceramic caliper grease and you should be fine.

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Friday, June 22nd, 2012 AT 1:27 AM
Tiny
MCJEEPIN
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Everything slides fine and goes together good when I first put it together but when I let it sit for half an hour and come back to try to move them, it feels like the grease has acted like a glue and frozen/dried? Then when I break it free of its stuck position, it works fine again but let it sit for some time and same thing happens.

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Friday, June 22nd, 2012 AT 1:33 AM
Tiny
RACEFAN966
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Ceramic caliper grease should fix that problem.

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Friday, June 22nd, 2012 AT 1:47 AM
Tiny
MCJEEPIN
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You think? I'm using synthetic. Will that really make the difference?

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Friday, June 22nd, 2012 AT 2:03 AM
Tiny
MCJEEPIN
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What about silicone? I'll pick up some ceramic based tomorrow. I guess I'll try ceramic first and if it doesn't work, could I try silicone based caliper grease? (If available)

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Friday, June 22nd, 2012 AT 2:12 AM
Tiny
CARADIODOC
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Most people don't even understand the importance of brake grease so kudos to you for that. It doesn't sound like you have a problem. The caliper is only supposed to slide 1/4" over the life of the pads. The rubber inserts stick and bend a little when you apply the brakes, then when you release the pedal, the sleeves relax an pull the caliper toward the rotor just a fuzz to release pressure on the outer pad. The square-cut seal inside the caliper works the same way to release the inner pad.

If you REALLY want to see a sticking caliper, (and a real poor design in my opinion), look at a 1980s Ford truck with their steel inserts. Now THAT'S a caliper that won't slide.

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Friday, June 22nd, 2012 AT 2:25 AM
Tiny
MCJEEPIN
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But its sticking so bad it WILL NOT "relax an pull the caliper toward the rotor just a fuzz"

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Friday, June 22nd, 2012 AT 2:54 AM
Tiny
CARADIODOC
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Maybe my fuzz is smaller than your fuzz. You won't see the caliper move;... Well, maybe it will twist a little if you watch while a helper works the pedal, but all you need to care about is that you can turn the rotor by hand when the brake pedal is released. If not, it's the piston that is sticking. Two things can cause that. Most commonly a ring of rust or mud has developed around the piston that is catching on the square-cut seal so it can't retract. That happens most often when the piston is pushed back into the housing to make room for the new thicker pads. I only worry about that when I can't pry the piston in with a small flat blade screwdriver before I remove he caliper. If you ever HAVE to resort to using a C-clamp, you have a piston problem.

The second cause is brake fluid contaminated with a petroleum product. You'll see the rubber bladder seal under the reservoir cap is blown up and mushy. On some models the flexible rubber hoses can become constricted too leading to pistons that won't release. You can identify either of those by opening the bleeder screw while the brake is stuck. That will release trapped fluid pressure.

That doesn't sound like what you're describing though. It might turn rather hard, but if you can turn the rotor by hand, you're okay. Keep in mind that when you're bouncing down the road, the normal play in the wheel bearings is going to let the rotor wobble a microscopic amount and that will help push the piston in and shove the caliper around. Unless I'm missing something in your symptoms or description, I don't think you have a problem.

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+1
Friday, June 22nd, 2012 AT 3:17 AM
Tiny
MCJEEPIN
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If you say so. But if I go down the road smoking, it's all you! =D

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Friday, June 22nd, 2012 AT 4:05 AM
Tiny
CARADIODOC
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If you go down the road smoking, you can't turn the rotors by hand.

What made you concerned with the calipers to start with? Did you just do a normal brake job or was there some problem you were trying to address?

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Friday, June 22nd, 2012 AT 4:31 AM
Tiny
MCJEEPIN
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My front left (driver side) caliper was not releasing in some way and caused the Jeep to pull hard left and strained the engine as well and I burned a quarter tank just short drive home (while taking frequent stops to allow caliper to cool off and small amount of smoke to clear.) You couldnt see the smoke going down the road but I could smell it and feel it. I rebuilt the calipers (new piston ring and dust boot) after cleaning it in a solution in a parts washer at the craft shop.

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Friday, June 22nd, 2012 AT 4:41 PM
Tiny
MCJEEPIN
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The problem I was trying to address was the sticking caliper. When I got home and jacked it up I could turn the whole wheel by hand with plenty of force but there was no way it was going to turn freely.
Therefore, I say the caliper was not releasing. Now I am confident the piston will release now but I think the slide/guide pins will NOT relax and will continue applying pressure on only the outside of the rotor.
(My rotors were barely warped but not that bad so I had them turned)

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Friday, June 22nd, 2012 AT 4:46 PM
Tiny
CARADIODOC
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This goes back to my comment about being able to pry the pistons in with a screwdriver before unbolting the caliper. Did you find a ring of mud on the piston? How did the chrome finish look after you cleaned it? If there were any rust pits, the piston must be replaced. Sanding the lifted chrome is not the proper fix for that.

I worked for seven years in the '80s at a Sears Auto Center where we mainly did steering, suspension, and brake work. On a typical day I would do two or three brake jobs and we rebuilt calipers and wheel cylinders on about nine out of ten cars. Our "All-In-One" kits came with all the seals and dust boots. In all of those hundreds of brake jobs we never obsessed about how hard the caliper moved sideways by hand. Our main concern was keeping every little hint of grease or any petroleum product out of any place it contacted brake fluid. We even worried about fingerprint grease. When reinstalling the pistons we needed to be able to work them in by hand until they were fully seated. If we couldn't, we did something wrong. In those days a replacement piston cost $20.00 and a professionally rebuilt caliper from the auto parts store cost around $90.00 so rebuilding them ourselves in-house made economic sense.

By the time I got to the dealership all through the '90s, rebuilding calipers was a lost art and few other people even knew how to do it. I rebuilt only three in the ten years I was there because calipers were not immediately available but the kits were.

Rebuilt calipers today are so inexpensive that it doesn't make sense to rebuild them yourself. The kits cost almost as much and you will never get the groove for the dust boot as clean as they do at the factory. If you have to replace the piston, you're guaranteed of having more money involved than just buying a rebuilt caliper.

Regardless whether you buy or rebuild a caliper, it still sounds like you're worried about a non-existent problem. If you apply the brake pedal, release it, then you can not turn the rotor by hand, you have a sticking piston. If you believe it's the caliper sticking on the metal tubes, you can prove it by prying the piston back in with a screwdriver through the large hole in the casting in the middle of the caliper. You can catch the piston or the pad to pry on. Even if you were able to move the piston, then still not be able to turn the rotor, I still would not concern myself with that because the forces acting on the caliper while driving are a whole lot higher than what you can do by hand. I mentioned previously the Ford truck calipers that were mounted with steel wedges with spring steel inserts. You needed a hammer, (that is not an exaggeration), to move those calipers and they just got worse once a little dirt got in there. That was considered normal and it was how they were designed. If you can slide your calipers by hand when you install them, put it together and go out and drive it to verify everything is working properly. No professional ever waited a half hour, then checked to see if they would still slide. If we did, we might find the same thing you did and we wouldn't get any work done.

If you still have a problem with a dragging caliper, there's three things to consider long before looking at how hard they slide. The first is they came with phenolic pistons. Chrysler had a big problem with those in the late '70s but not much after that. They would grow and stick. The only cure was to replace both of them with chromed steel pistons. Most manufacturers now use phenolic pistons to save weight and they rarely have a problem.

The second thing to consider is a restricted hose. That has been a fairly common but elusive problem on other models that have a metal bracket crimped around the middle of the hose. Rust builds up inside that crimp and constricts the hose. Pedal pressure will force fluid through to the caliper, but the square-cut seal deforms, then straightens out to retract the piston a little, and it's not strong enough to push fluid back through that restriction. You can identify that by stopping on a slight incline, in neutral, put a wheel block a few inches downhill, then crack open a steel line at the master cylinder. If the brake releases, or if multiple brakes are staying applied, you have contaminated brake fluid, or the power booster push rod is too long, (if work related to that was just done). If the brake doesn't release, crack open the bleeder screw on the stuck caliper. Now if it releases, suspect the hose. Your hoses don't use that metal bracket but there have still been instances where they trap fluid.

As long as the piston is releasing properly, a caliper sticking on its mount can't cause that brake to drag. There is way too much play in the wheel bearings to maintain that drag. Either the rotor is simply going to move away from the outer pad or it's going to be bounced around and will pound against the outer pad forcing the caliper to move. Under normal conditions the piston and caliper only release a few thousandths of an inch. That's the equivalent to the thickness of a sheet of paper.

The third thing that has me the most concerned is the type of cleaning chemical you washed the calipers in. Many of them are petroleum-based and not acceptable for cleaning any brake components that contact brake fluid. Some of them use a chemical to dilute fuel oil. The only thing that should ever be used is brake parts cleaner which is most commonly found in spray cans. It is even better than carburetor cleaner in that it takes longer to evaporate giving you a longer working time to scrub parts. I don't recommend carburetor cleaner either due to the risk of it also being petroleum-based. It is meant to evaporate quickly as it goes into the engine, and that defeats its purpose of hanging around long enough to give you time to clean parts. If the cleaner you used has any hint of petroleum in it, including from parts the previous people washed, you have contaminated the entire brake system and repairs will be very expensive. Calipers are made from cast iron which is porous and will absorb those chemicals. Those chemicals will continue to leach back out and recontaminate any new fluid and parts. The fix for that is to replace every part that has rubber that contacts the fluid, and flush and dry all of the steel lines. That includes wheel cylinders, calipers, combination valve, master cylinder, and rubber hoses. If the vehicle has anti-lock brakes, the hydraulic controller must also be replaced since it has rubber 0-rings and lip seals.

Every year I did a demonstration for my students to show the importance of keeping brake parts clean. I had two small beakers, each with an inch of brake fluid, and in each I dropped a lip seal from a wheel cylinder rebuild kit. In one I also placed one drop of power steering fluid. One week later the seal in the contaminated fluid had grown by over 1/8" in diameter and was soft and mushy. The rubber might still seal but the square-cut seal in the caliper is meant to stick to the piston as it is applied, and it deforms slightly because of that. When pressure is released, the seal straightens out and pulls the piston back with it. Being soft and mushy, it will not pull the piston back. In the master cylinder the lip seals will expand and grow past the fluid return ports blocking them off just as if you were holding the brake pedal down a little. That will lead to both front brakes dragging. On split-diagonal systems found on most front-wheel-drive cars, one brake will always be affected first, then the second one days later as the contamination spreads. Rear drum brakes will not drag because the shoe return springs pull the shoes back as the brake pedal is released.

I'm really nervous about what was in the cleaning chemical you used. That is a lot more significant than not being able to slide the calipers on their mounts. I shouldn't even say this, but you might want to replace both calipers and both rubber hoses, run new brake fluid through the steel lines before the new hoses are connected, until clear new fluid comes out, and hope no contamination has spread beyond that. Replacing just a few rubber parts is not the way we teach doing conscientious work but given the cost of replacing everything, and the fact the work was just done recently, you might very well get lucky and avoid the bigger expense.

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Friday, June 22nd, 2012 AT 6:45 PM
Tiny
MCJEEPIN
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I have not installed the rebuilt calipers onto the Jeep yet. It was some acidic stuff that a pump cycles out the faucet, down the drain and back through the faucet. However I don't see how this solution could contaminate the brake system because after cleaning them, I sat them to the side to air dry. Sooo, what your saying is, the molecular hints that the solution may have left behind in the cylinder could contaminate the whole brake system and ruin all rubber seals and lines?
Appreciate the in-depth answers =)

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Friday, June 22nd, 2012 AT 7:07 PM
Tiny
MCJEEPIN
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OH! And I DID in fact use brake parts cleaner even after the solution I had cleaned them in. So does that mean I'm good to go? Does brake parts cleaner cut everything that could possibly contaminate the brake system?

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Friday, June 22nd, 2012 AT 7:12 PM
Tiny
MCJEEPIN
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Maybe this will help.
Here's the order in which I cleaned/rebuilt them.
1) Cleaned with mysterious solution =/
2) Sprayed multiple times with brake parts cleaner inside and out.
3) Lubed cylinder, O-ring, and piston with brake fluid and put together.
4) Have yet to install because fear of screwing something up.

Thanks

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Friday, June 22nd, 2012 AT 7:17 PM
Tiny
CARADIODOC
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Yup. Even if the cleaning solution is not petroleum-based, you don't know what someone else cleaned in there previously. "Safety Clean" is one common trade name. The guy comes around about once per month to remove the dirty stuff and add new clean chemicals. My understanding is it is not made from a petroleum product, but we commonly washed wheel bearings in it. That grease IS petroleum-based and would contaminate the calipers.

Again, this is something I shouldn't be saying out loud, but if you rinsed the calipers with water and let them dry, it is very possible you will not have any problem with them. Being the cheapskate I am, I would put them on my older cars but I would not trust my reputation by putting them on a customer's car. All of my cars are older than yours and parts are inexpensive so it would be my own fault but not terribly expensive if I had to replace everything. The exceptions are a '95 Grand Caravan I have with anti-lock brakes. Two rebuilt calipers is cheap insurance against the heartache of having to replace the hydraulic controller. I have a '93 Dynasty too with ABS but that only has 4,200 miles on it so it won't need calipers for a while, but still, I would trust myself to rebuild them if necessary, but I wouldn't trust anyone else due to I can't watch or control how they clean them and that hydraulic controller is also expensive.

You also have to keep in mind there are things we do and there are things we tell other people to do, and they aren't always the same. There are shortcuts we take but you have to give do-it-yourselfers the entire procedure because they don't know yet where they can safely cut corners, and every case can have different variables.

I've been involved with an early '70s Ford station wagon the guy just bought. The previous owner put automatic transmission fluid in the master cylinder. Only the right rear brake was still working a little. I had a mid '80s Chrysler K-Car that the owner claims someone put power steering fluid in the master cylinder, (I suspected he did that himself). And I bought a '59 Edsel at an auction not knowing the master cylinder was filled with automatic transmission fluid. It took a full tank of gas to go 55 miles to an old car show and halfway back home before I ran out. Once home, the right front tire skidded all the down my granite driveway.

In all three of those cases, the contamination was very apparent and it the master cylinders were completely full of the stuff. That is greatly different than what could have happened on yours, but here's two examples of what can happen on the other extreme. We learned from one of the Sears training schools that there had been a rash of fluid contamination problems and complaints all related to one store in California. Back in those days in the '80s, there were only a few master cylinder designs so we needed only a few adapters to use a "bleeder ball" to pressure bleed our brake jobs. If you aren't familiar with that, it's a round ball with a rubber bladder in the middle, similar to a water tank for a home well system. You fill the top section with up to 5 gallons of new brake fluid, then pressurize the bottom with up to 15 pounds of air pressure. Well, we needed a funnel to pour that much fluid in from a big container. After investigating, it was found that one fellow in that shop grabbed a funnel that was regularly used to fill engine oil and automatic transmissions, wiped it out with a clean rag, then used it to fill the bleeder ball. THAT residue was enough to contaminate the entire five gallons and cause problems in at least a dozen cars.

The second story we were always warned about used to be more common when cars had front wheel bearings we had to repack during the brake job. Uninformed people would often wipe their hands on a clean rag, then when refilling the master cylinder, it was normal for that rubber bladder seal to be pulled out of the cap. They poked it back in with their fingers that still had some grease residue on them, and that was enough to cause problems.

So there you have the extreme cases and the not so obvious ones that I can share. For every one of those that give us trouble, there are some out there that never cause a problem. Hopefully I gave you enough information so you can decide how to proceed. What I find interesting is that more do-it-yourselfers, and even some "professionals" don't run into trouble over this issue and it isn't more widely known.

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Friday, June 22nd, 2012 AT 7:50 PM
Tiny
CARADIODOC
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Your last two replies showed up while I was still pecking on the keyboard. I mentioned that calipers are most often made from cast iron which is porous, but they aren't a sponge. It takes time for contaminants to soak in. From what you described, particularly finishing up right away with brake parts cleaner, I would suggest it sounds like you are going to be okay. Notice how carefully I danced around that answer. We always have to be careful so we don't let you cause a problem, but I think you're going to be okay. At this point my biggest hope is that you found something on the left piston that would have caused the dragging brake.

Thinking back to my story on constricted hoses, now that the calipers are off, if you find brake fluid dripping from the hoses, they aren't constricted. By the way, to prevent that so you don't have to bleed air from the entire lines, use a stick from the seat to the brake pedal to hold it down two inches. Gravity won't be strong enough to pull fluid past the lip seals. You can remove the brake light fuse or disconnect the switch if you'll be leaving it like that overnight.

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Friday, June 22nd, 2012 AT 8:00 PM

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