This weekend I replaced the rear disc pads and rotors on my 99 F150 4x4. The rotors were difficult to remove but came out with a little coaxing from a 3-jaw puller. I noticed the pads were quite difficult to install because it seemed they were rather tight inside the slide rails. I was carefull to grease the slide rails with a caliper grease. All seemed fairly straightforward on the install. But now there seems to be noise from the rotors and pads which doesn't seem to get louder or go away with each press of the brake pedal. Just a constant low level scraping sound a bit like what was going on prior to replacing the pads. It almost seems that the rear pads are not engaging at all. Stopping power on the truck is OK not much of an improvement over what I had before.

Are the pads frozen on the slide rails?

 

Remove the rotor & see if pressing the pedal causes that pad/piston/caliper to move.

Did you check the parking brakes?

 

I wouldn't press the pedal with the rotor removed - you are likely to spit the piston out and create a whole new problem.

Better to put the rear up on axle stands, pull the wheels (leave the rotors!) and have someone operate the pedal while you watch the calipers. Try to move the rotors with the pedal pressed to see if they are clamping at all.

The calipers float, so make sure you can move them inboard/outboard a little with no brake pressure applied.

It is possible you got the wrong pads, too. If you pressed the pistons back in all the way before changing out the pads and they were still very tight to slide in, they may be too thick for the new rotor.

The rear discs were a mid year change on the 99's (I know, 'cause I had to wait for delivery of mine because of it) and not everybody's parts book seems to be right.

Also, the parking brakes are a drum type inside the rotor, and the shoes have been known to separate from the backing plates. Double check those when you take it apart again, and verify the adjustment.

 

I'd take a look at the internal drum type parking brake shoes. You said you had to pull the rotors with a 3 jaw puller. If you had to use that much force, you almost certainly damaged the linings. The other thing that has been done more than once (even by expeienced folks) is putting the pads in backwards with the lining material facing the rotors.

 

WTH are you talking about? Hopefully you arent suggesting he does that on the rotors. I wouldnt even do that on the parking brake.

And if you needed alot of force to get the rotors off, you may have warped them slightly, and you are getting the noise. But to some extent you should hear a very slight sliding noise when you spin the rotor.
-Patrick

 

But I've always made sure the lining material faced the rotor....

I know what you meant to say, and find it very scary, but I don't doubt it has been done.

 

I second the parking brake claim, check into that because it sounds siezed in a position that is somewhat set. As long as the pads slide nice, say with antisieze they should be fine. I always antisieze all pad contact points to say the piston and any/all backing. I suspect the parking brake, it's common, but fairly easy/cheap to fix.

 

Thanks for the ideas. I'm sure that I did not put the pads in backwards. I believe that it is a good possibility that I somehow damaged the e-brake linings. I was really waling on those rotors to get them off. I'll check them as you guys indicated...jacking up the rear end and spinning the wheels. In any event I think the pads are not "free floating" in the caliper because they seemed really, really tight when I placed them between the rails. I'll check that too at the same time. Is there any possibility that the calipers were damaged (from the c-clamp) when I seated them to make space for the new rotors and pads?

 

That's a bit dramatic, don't you think? Have you ever tried it? It takes SEVERAL pumps to fully extend the piston, so you'd have to really work to shoot it all the way out.

 

Nope never tried it, since I didn't want to spit the piston out.

I figure if all the other brakes are limited to a couple mm of travel, and you pump the complete volume of one stroke of the master cylinder into the system, you could extend the piston on the one unencumbered caliper quite a way. Maybe all the way. Two pumps and you have an even better chance.

If the piston sticks and doesn't move with one pump, someone might give it another. The pressure builds, (rubber hoses storing energy) and then the stick releases....

I just figure it is better safe than sorry. No intention of drama, just safety.

 

If the piston sticks, it's STUCK. A master/slave hydraulic brake system is built to multiply the force on the slaves to more than 12x what your foot puts on the pedal, and pumping the pedal doesn't "add up" that force. It gets released each time you pump.

And the brake system is specifically engineered NOT to "store energy". Think about it - normally, they all "stick" (stop when the pads hit the rotors), so if the hoses could stretch like you're describing, they'd do it all the time, and burst.

But even with only 1 slave moving, the master still doesn't push enough fluid in 1-2 strokes to eject a piston that starts off fully retracted.

 

did you possibly bend the dustshield in your efforts to remove the rotors? This is one of the biggest problems brought to dealers/mechanics following a DIY brake job.

 

check to see if the indicator strip on the pads got bent inward. Just a thought..

 

Something that you need to make sure of when doing brake work is to open the bleed port when pushing in the caliper piston. That goes for front or rears. Any car or truck that is after 98 can have damage to the ABS manifold. They are more expensive then rotors, pads and calipers combined!! Check the adjustment on the rear parking brake they adjust like old-school drums. I know I am a mechanic.

 

That's a MYTH. Ford does NOT recommend that, for several reasons. And 4WABS has been around since '93, anyway. Every time you release the brakes, fluid is forced back from the calipers to the MC, just like when you compress them to change the pads. And there's nothing in the modulator that could be damaged, either. It's just a couple of valves on each line. When the ABS is NOT active, fluid just flows straight through, in either direction.