MC and brake probs???

My buddy's 98 Cummins 2500 front brakes are sticking. Once they are cool you can drive for a bit then they get hotter and hotter to the point you almost can't move. Kinda thinking it is the master cylinder and it is presurrizing up the back side of the plunger and making the calipers not be able to retract basically. Does this sound kosher or anyone else seen this or have any ideas? If so would a MC off something like a V10 rig or anything else fit it if we can find one in a salvage yard? Need something cheap and quick basically. Not sure if the gassers have hydro-boost either. Any help is appreciated, thanks.

 

Dragging Brakes

Mnorby:

Before you guys pitch the MC as the cause I'd consider investing in a caliber rebuild kit for each of the front calipers. The other option is to buy a couple replacement remanufactured front calipers for your friend’s truck. Disc brakes tend to drake once the slide pins get grunged up and no longer permit the pads to retract the slight amount they need to pull back off the rotors to prevent the drag your friends front wheels are experiencing. My experience with what your guys are going through is that when cold the rig will drive but after a few miles and use of the brakes a few times the pads begin to drag, heat builds up, the wheels get hot and soon mileage drops dramatically as the pads clamp harder and harder onto the front discs. It's a no win situation and will require either the rebuilding of the calipers or replacement with either new ones or the cheaper alternative of remanufactured ones. Once replaced a quick bleeding of the two front brake lines and the brakes should be like new again and good for thousands of trouble free miles.

Anyway from what you describe if it were my truck and my money the above is where I'd invest my time and $$$ to resolve what I think is causing the brake drag scenario you describe. Others may agree or have another solution.

George

 

I will second a caliper problem but I do find it suspicious if both calipers are doing the same exact thing.

 

I still kinda rule out calapers because both sides are doing it equally and never had any problem with either side till now. I think it would have to futher up the line

 

If both front calipers are locking up and not releasing then it would have to be the MC. Try to get them to stick again and break loose one of the bleeders to see if fluid comes out and the front brakes release.

 

That was something I was kinda thinking, drive it so they start to lock then crack a line at the MC, if they release then sould be the MC. If not then go to the next connection down the road and crack it and see and keep doing that till they rele3ase and the problem would be before the line that we cracked and bled off. Does that sound logical?

 

Totally logical waytogo

 

I'm sticking to my Caliper Theroy

I did a brake job on my 1999 Jeep Grand Cherokee this spring. Did fronts and rears, new pads and rotors since the original rotors were starting to warp and I'm not into turning them as they simply warp again soon after being turned. Now you ask why I claim the calipers are the suspect in your friends brake dragging issue. All four of my brakes began to drag on my first test drive after swapping out all components except the calipers. By the time I got my rig home I could have fried an egg on the front rims. Hubs were smoking! I'm talking HOT not warm. I tore all four brake systems apart a 2nd time and rechecked all my work, cleaned and regreased the pad sliders and this helped slightly but I was still not able to drive more then a few miles before the front and rear rims were hot to the touch. Using a friends infra red tester my fronts were running 250 degs F and were much cooler then after my initial pad and rotor replacement. I replaced the front calipers with remanufactured ones and rebuilt the rears with new slides, pucks and seals. The caliper slides and pucks get corrosion, road grunge, you name it and the pucks and slides just back of slightly when the drivers foot is removed from the brake pedal, the MC lets off the pressure in the brake lines and the pucks pull back slightly, sliding on the slides every so slightly to release pressure on the backs of the pads and releasing pressure on the discs. Any pressure remaining on the backs of the pads results in HEAT, worn pads and discs and reduced fuel economy.

When you put new pads in the caliper you force the pucks back inside the caliper and the pads start riding on the dirty and worn part of the slides. This process either works or it doesn't. When it doesn't you get IMHO what you’re describing on your friends truck. Brake drake, increased heat and he'll soon need another brake job to replace the worn out pads that drag as he drives around. This drag won't go away by driving it.

The theory of driving the truck till the brakes and wheels are hot and then checking the bleeder for pressure will most likely find pressure in the brake lines since the pucks are not able to retract correctly from the backs of the brake pads because the slides are not letting the pucks pull back and letting the pads release their grip on the disks.

I know exactly how you feel trying to figure this out. I went through the same head banging while my Jeep could not be driven without damaging my newly installed pads and discs. In speaking with several outlets that perform brake work around where I live they never do brake jobs around here without replacing the calipers or at a minimum rebuilding them, new slides, pucks and seals so that the above process operates smoothly. Granted I live in an area where it rains a lot, lots of road grime, seasonal chemicals for road ice etc. All this results in an increased cost of putting miles on rigs up here in Juneau, AK. The cost of a brake job front and rear runs well over $1,000.00 since mechanics won't screw around with used pads, used discs or calipers unless they replace or rebuild them before reassembly the disc brake system. Things may be different where you live but your description of what is happening sounds like what I went through Like was said above there wasn't a problem with the system before the pads were replaced. WHY NOW? I don't think your MC just went south and I know you've done some things to the calipers that will effect their correct operation. Because the new pads require stuffing the dirty pucks back into their seals and trying to get the pads to slide on an area of the slides where it's been exposed to a worn area on the slides. This results in the slides not working easily when you take your foot off the brake and you get pad drag on the discs.

Good luck

George

 

Good description. Do you suppose the calipers could be at fault even though no work or anything has changed on them for as long as I can remember from him and the previous owner and both sides happen to go out at once? I could see it if we had done a brake job and pushed the calipers back for the new pads or something. He was driving down a dirt road with mud that could have gotten on the calipers though but still boggles me they both do it at the same time.

 

I may stand corrected...

In re-reading your original post and I "assumed" or read into your post that you guys had tinkered with his brakes. The fact I now see nothing was mentioned in your original post regarding servicing his brakes that's a tuff call. I screwed mine up. I went from a slight pulse when braking and knew it was time to work on my Jeep Grand Cherokee. The late 90's and 2000 are known for their warped rotors so I had new aftermarket slotted and drilled rotors and pads waiting in the garage since the Jeep was new. Got a good on line deal so I bought them with the intention of using them way before spring of 2005. As it turns out the factory OEM brakes did ok given the fact they are being used in a very nasty wet and cruddy environment I live in. Especially the stop and go with rutted pavement so it is common to brake from 60 mph to 0 and splash cold water up on the brake components. So brakes up here go through frequent heat and rapid cool cycles.

SO, I don't know much about master cylinders. From my mechanical past the only experience I have with one going bad was on a half ton 1979 Chevy Silverado pick-up. When fluid started running down the firewall it was obvious there was a problem.

BUT, I can say from my Jeep brake job looking at the OEM pads that I removed, the fronts were toast. My brakes had been dragging prior to my diving into the project. They were wedge shaped due to them dragging way before I noted the warpage/pulsing brake pedal issue. I instantly gained between 1.5 and 2 mpg by doing the brake job due to the brakes dragging.

Tuff call. If I were in your and his position I'd have to consider the mileage on the existing brakes and the conditions they are used in. If he's got a lot of miles, 10's of thousands on the existing brakes or as you stated ran through muddy goo or some such crud.

I just don't know. I have done auto and motorcycle caliper rebuilds and that's the limit of my experience with home shop mechanic experience. If I had to bet my next pay check I'd pull the front tires off and have a look see at the calipers. If they are all curded up with mud or road grunge then clean em up with a garden hose and a brush and get the caked crap off the calipers since I'd bet they are hanging and not letting the pucks release from the back side of the pads.

Normal servicing of disc brakes should include cleaning and putting fresh grease on the pad slider pins.

My experience with disc brakes is they are trouble free till they need servicing and then they need TLC to clean up and or replace the bits and pieces that permit them to function correctly. When you let off the brake pedal, the fluid pressure releases slightly and the rubber seals that hold the pucks in place let the puck retract just enough to take the pressure off the back side of the brake pad, thus releasing the grip the pad has on the rotor. Your buddy still has grip and I have no idea what function a master cylinder has on this process. I do know the calipers can cause the explained symptom so that's where I would look first and why I jumped to conclusions as to the cause of his trucks brake drag.

So from Alaska I wish you luck figuring out your buddies brake issue. Be sure and post once it's resolved so we can all learn from his experience.

Thanks,

George

 

I drive the craznap outta my truck (mountains, water, mud, sand) and i regularly have to tear the clipers down and grease the slides to prevent dragging. Sometimes one side drags and makes it pull. I HATE that! I think maybe the clipers need the internals rebuilt every so often too, best way to do that is to get remans. my .02

 

Pump up the system till they drag then start crackin' the bleeders loose or line fittings till they release then you'll KNOW where your problem is.
BTW stop messin' around and get it fixed. Brakes aren't anything to be playin' around with. oke:

 

waytogo

 

ya, the truck is shut down till it is fixed. I drove it today for myself and after about 4 miles you could feel the drag. Only $12 for rebuild kits so I think I'll do that first for him since it is cheaper than $130 for a MC and it prob wouldn't hurt to do them anyways. Thanks for the help.

 

Thats why we are here waytogo opcorn:

 

What all is involved in greasing/ rebuilding the callapers? I have never done that.

 

take 'em off - don't touch the brakes while you're working on them! you may need a large c clamp to push the cylinders back in to reinstall. pound the mounting bolts out of their holes, they havle little sleeves on them, clean the sleeves and holes (rubber) good, grease (with brake caliper or disc brake wheel bearing grease) and reinstall. i'm thinking about trying to make some greaseable.....

 

Make sure to open the bleeders while pushing the calipers pistons in.
It really screws up the ABS when pushing the brake fluid back into the master cylinder :doah: .

 

what about rebuilding? Thanks again

 

dunno, sorry! get rebuilt ones...not expensive i think autozone warranties them.