Front Brakes Draggin' Me Down

[Rebelrodder]

Howdy!

 

I'm having some brake drag coming from the calipers in my truck. Here's a little background on how I got here:

 

Worn out ball joints started me down the rabbit hole of a front end rebuild. I've got new ball joints, hub bearings, rotors, brake pads, track bar and steering box brace. The good news is it drives about like it should tho new TREs are in the near-ish future. That should finish things up and make it all good under there. I changed the pads and rotors because they were old and thin and the truck had started pulling to the left under moderate braking. Hard braking was straight as an arrow. Go figure...

 

After I installed all this new hardware and took it for a test drive, I came home to a lovely face full of hot brake smell. Investigation showed that the calipers were dragging on both sides but the right side was worse. The calipers got new rubber bushings and lots of fresh grease on the guide pins when the pads were installed. I tried bleeding at the calipers only to find that the bleeder was rusted shut down in the caliper bore, so.....  off to the parts store for some fresh reman'd calipers and the flex hoses that feed to them.

 

I bled the front part of the system carefully, I know there is no air in there. The rub (literally) is that the calipers don't seem to be releasing very much. They do loosen up when the brake pedal is released and the drag on the rotor is light but, it is still there as is evidenced by what i feel like is excessive temperature on the hub flange where the wheel mounts. After a 12 mile trip to work I can hold my fingers on that lip on the hub. The right side is warmer than the left and I don't burn my finger tips but it does seem warmer than a bearing should get. That's part of why I'm chasing root causes of brake drag. As a further complication, the left pull under moderate braking is back though it is less dramatic than it was before.

 

I've done some digging on various forums and the main causes people seem to find are the flex hoses going bad and the calipers sticking on the guide pins or the anti-rattle springs. I'm thinking that I can bypass the hose part since mine are new. I'm pretty sure I don't have any anti-rattle springs because they don't seem to exist on 99's with single piston calipers. They weren't there to take off and didn't come with the new calipers. I've read that the calipers should slide easily on the guide pins but mine do not. They barely move at all even though there is plenty of evidence of grease on the pins and hopefully in those rubber(?) bushings. Should the single piston calipers move easily on those pins? I don't see how they could since the bushings fit so tightly on the steel pins that the caliper bolt goes thru. If they are supposed to slide on there, how do you keep the grease in there to lube it? Anybody have suggestions for that?

 

This weekend I'm going to do a complete brake system flush and bleed in the hopes that my issue is really hydraulic in nature rather than sticky guide pins. I'm hoping it is as simple as some debris being pushed up out of the crapped up caliper and blocking some port or other in the metering block/proportioning valve. I'll keep an eye out here of suggestions and post any solutions I might find.

 

Thanks for reading my novel!

 

Jerrod

[joecool911]

Your front calipers are doing what my rears were doing before I rebuilt mine. I suppose re-man calipers could be not operating properly. But you were so close to rebuilding your own. Just making sure pistons fall into the bores on their own weight without the seal in the bore

The time to flush the brakes was before new or rebuilt calipers were installed.

Edited March 15, 2014 by joecool911

[diesel4life]

When you say the calipers don't slide freely on the pins, this is with new pins correct? Keep in mind when greasing certain components that have a "blind hole" that too much grease will fill the void and limit the travel of the pin into the bore.

[Rebelrodder]

diesel4life,

 

Yes, I have all new caliper hardware; bolts, steel sleeves and rubber bushings. All of the pieces are through hole. no blind holes to pack with grease.

 

The way I'm thinking about it, the calipers only move on the steel sleeves in order to compensate for wear on the outer pad. The rubber bushing must act as some sort of vibration isolator. I think this is the case because the steel sleeve is only about a quarter of an inch longer than the rubber bushing itself which really leaves very little room for movement. The sleeve gets pinned solidly between the knuckle mountng face and the head of the mounting bolt. In this case, it wouldn't really matter if the caliper slides freely or not as the force during braking should be more than enough to advance the caliper along the sleeve as the pads wear down.

 

This leads me to the notion that the brake drag I am experiencing is hydraulic in nature and must lie between the master cylinder and the calipers. I'll start there and see what I find. I'll also check the rear drums to make sure those are working OK as well.

 

Does this make sense or am I all wet?

 

Jerrod

[joecool911]

After rebuilding my calipers and greasing the pins, with pistons retracted all the way I can move the caliper back and forth with little effort. Did you grease things good?

Master cylinder and rubber brake lines are about all else I can think of. I sure rubber brake lines are pretty cheap. Might be a place to go next.

Edited March 16, 2014 by joecool911

[Rebelrodder]

joe,

 

Oh yeah, i greased the heck out of it just to be sure! Rubber brake lines were replaced along with the calipers. I'm really hoping I just pushed some crud up from the calipers that's playing havoc with the metering valve and will be easily flushed out.

 

I noticed that you have an 01.5, do you have the dual piston calipers? Mine are the single piston kind. I think they may work differently. I'm still working to confirm that.

[MnTom]

Try opening a bleeder and after a few seconds close it on one of the calipers and see what they both feel like. If they start turning easier then you know it is hydraulic in nature. If not, then it must be mechanical. Since you have all new slides and pins along with new calipers it is doubtful that the problem is any of those. If by chance the bleeders squirt just a bit then I would suspect a master cylinder problem first. You may have a piston in it (there are two pistons) not returning all the way.

[joecool911]

joe,

Oh yeah, i greased the heck out of it just to be sure! Rubber brake lines were replaced along with the calipers. I'm really hoping I just pushed some crud up from the calipers that's playing havoc with the metering valve and will be easily flushed out.

I noticed that you have an 01.5, do you have the dual piston calipers? Mine are the single piston kind. I think they may work differently. I'm still working to confirm that.

Yes, mine are dual piston calipers. Above suggestion sounds good. Bleed off and see if they still drag.

[Rebelrodder]

MnTom,

 

I'll give your suggestion a try when I get to work on my truck this weekend. My weekends are a little different than most. I'm on S,M,T and every other W. It's a cool deal in the summer when I go camping!

 

 

J 

[Rebelrodder]

I meant to say off on those days... Sheesh! It's been a bit of a long week! 

Edited March 16, 2014 by Rebelrodder

[MnTom]

I know the feeling. When I was working one of the last jobs I was on I wound up with one day off in seven weeks working nights, no less. You get to where you don't know or care what day it is anymore.......

[Mopar1973Man]

Your front calipers are doing what my rears were doing before I rebuilt mine. I suppose re-man calipers could be not operating properly. But you were so close to rebuilding your own. Just making sure pistons fall into the bores on their own weight without the seal in the bore

The time to flush the brakes was before new or rebuilt calipers were installed.

 

This is a common issues that people don't check the piston to bore clearance. It will cause the piston to bind up and stick.

[Rebelrodder]

A quick update is in order.

 

I got to really dig into things this weekend; after bleeding the heck out of the front brake circuit I got all of the old fluid out and probably wasted a good bit of new stuff. But at least I know it's good and fresh in there!

 

I verified that the calipers do slide easily on the guide sleeves once the pads aren't there or at least the piston is retracted to leave some space. I tracked down my problem to a suspected hanging piston in the right side caliper. NAPA swapped me for a different one and I seem to be good to go now. No more dragging brakes! Woohoo!

 

One last question about how the brake system works. When I was checking to see if there was a hydraulic reason for the drag I never got any spurts of fluid as if there was some residual pressure at work. What I do have is a slow but steady flow from either bleeder that does not stop whether the cap is on the MC reservoir or not. Is this how it's supposed to be? I makes sense to me that it would work this way since the reservoir is above the bleed screw where the fluid comes out. Gravity/atmospheric pressure should make this happen, right? This should be the basic principal behind gravity bleeding the brakes, correct? 

 

Sorry for the newb questions. I'm still learning a lot about how brake systems are supposed to work.

 

Thanks!

 

Jerrod

[joecool911]

You can actually gravity bleed brakes if you have the patience.

Mark your maintenance checklist for 30-50k miles down the road. Order seal kits for the calipers. Take em off and pop out pistons. Make sure the pistons slide back down fully under their own weight without seals. If not, sand them down until they do so. Replace seals and dust caps and you're good to go. You should never have to buy calipers again. If you can remove calipers and bleed, you can rebuild calipers. Mike has a good video on removing pistons with compressed air. Keep fingers out of the way? Puts a pretty good divot in the 2x4 when they come out!

When I rebuilt mine, I shot a good amount of brake fluid through the brake line hole and shot the pistons back out and pushed them back in a few times to get everything lubed up nice. Then the pistons pushed back into the cylinders easy. Before this pistons were hard to push in. Dry seals even though I did lube them before assembly. Gave me piece of mind that the seals were properly seated too. Plus the dust covers stretched a bit and seated really nice. Just let them hit the 2x4, but don't remove them. It's fun to shoot those pistons out!

Edited March 21, 2014 by joecool911

[MnTom]

Your bleeders oozing fluid is 100% normal.The only time they would spurt fluid is if there is some pressure on the system.

[Rebelrodder]

Caliper maintenance in on 30 to 50 k puts me out about 4 or 5 years. Is that too long to wait? I was thinking about flushing new fluid through annually just to be safe. it's so cheap that a rebuilt caliper to replace a bad one will buy several quarts of the stuff.

 

Oh, one last thing. I see all over that you should use brake fluid from a sealed container only. Does that mean that the cap was screwed on while it was in storage or only cans with the little foil seal stuck on top? Essentially, how sealed is sealed?  Western Oregon is a wet place. I want to be sure my stored fluid is still OK to use.

 

Thanks!

[Rebelrodder]

On the topic of caliper rebuilding, How difficult should it be to push the piston through the seal into the caliper bore? I admit that I took apart the suspect unit I returned to NAPA.  Just for the fun of satisfying my scientific and mechanical curiosity.   It took a lot of air pressure to pop it out. Once out I found a few bits of seal in the bore. With the seal out of the way, the piston slid through smoothly. When I tried to reassemble it that's when things went kooky. I ended up using an H frame press to get the damn thing back  in there. Is this normal? If not, I think I might know why it was hanging up!  Friday night special?!  

[joecool911]

I think on the fluid question it depends on how much fluid is gone. Full there is not much air in the container to hold moisture. Half full a lot more potential for contamination.

I think that if the calipers were put together even with lube that sitting around the seals could absorb and become dry. Combine that with offshore labor and you end up with an inferior product. Another reason to do them yourself. $4 per caliper from Rock Auto.

Upon assembly it can be really hard to get the pistons in the bores. I used a big C clamp on mine. Once I put brake fluid in the brake line hole and shot the pistons in and out a couple times they took maybe 20% of the effort as initially.

Edited March 22, 2014 by joecool911