[weitekampt]

I did another brake job today. While doing the job, my caliper hangar slipped and the caliper fell so the lines were tight for a second. after finishing the job, I noticed that I have a fast pulse in the brake pedal. After a while of thinking, could I have damaged the vacuum line for the abs? I think one of those lines is for the ABS anyway???? What could I have done to make the pedal go funky? Just rotors and pads.

HELP! /ubbthreads/images/graemlins/confused.gif

 

[AutoJim]

No vacuum or vacuum lines for ABS, or for the brakes at all on our trucks. The hydraulics for ABS are inline between the master cylinder and the wheels. There's also a wire for the wheel speed sensors (if you have 4WABS, not RWABS).

Causes of pedal pulsation are numerous, but the most likely on our trucks is rotor thickness variation. Since you just replaced the rotors with new ones, though, I'd look to see that the new pads are correctly installed and the little sliders they rest on are okay (if you didn't replace them) and in position -- and that the caliper slide pins are free to move. It's *possible* that you damaged the soft hose when the caliper dropped, but I'm not really sure that would cause pulsation.

When the ABS hits, you'll know it. It almost never kicks in on light to moderate stops unless you happen to go over a bump during braking, in which case it can get momentarily confused as wheels unload and try to lock up.

 

[weitekampt]

AutoJim,

I was wrong. Sorry. I'll give you a scoop on the details. The rotors that I replaced are the originals. I had them turned and the guy said that the didn't even need it. Slight grind. I put on the napa pads...lifetime guarantee. I replaced all the clips and placed a light "film" of synthetic brake lube on the clip surface where the pads slip in. Also took apart the slide pins and cleaned them up real good along with a good coat of synthetic brake lube. It seems like I covered my bases, but concerned about the very rapid pulse. Just like the pulse you get when the abs kicks in.

Well, if anybody else has some suggestions or advise I would greatly apprecaite it.

Thanks again AutoJim. I'll look at those things today!

 

[Roadfrog]

When I got my rotors back from the shop that turned them, they told me that they were fine and that they hadn't really needed turning. When I put them back on the truck though, my pulsing was gone. Maybe the rotors are so big that it's harder to tell that they're out of true in comparison to all the smaller rotors that are turned. /ubbthreads/images/graemlins/shrug.gif IMHO, you had the rotors out and mybe should have just had them turned as part of the maintenance you did anyway.

 

[Larry P]

The problem......the stock rotors are crap. When I got my truck the front rotors were warped. Vibration and pulsing when the brakes were applied. I took them off and had them turned. 10K later it's coming back. Yeah, I know....quit riding the brakes, well, I don't ride the brakes. I live in the mountains and use my gears and virtually never ride my brakes. My 97 had 97K on the rotors when I traded it in and they had never been turned through 3 sets of pads.

I plan one more turn of my rotors...this week, because I CAN'T STAND vibrating brakes. If it starts again I'll be going to the slotted rotors (Slotmasters??) and new pads to solve the problem for good.

Larry /ubbthreads/images/graemlins/cool.gif

 

[NCHornet]

Larry,
I was in your exact position last week and I don't tow in the moutains!!!!
Take the money you would spend having them turned and apply it to cyro'd powerslots and Hawks Superduty pads, and be done with it.
I ordered mine last week and hopefully can install them this weekend if they arrive on time.

 

[Roadfrog]

[ QUOTE ]
I plan one more turn of my rotors...this week, because I CAN'T STAND vibrating brakes

[/ QUOTE ]

Me neither. Just realize though, that everytime you turn them, the vibration will come back all the sooner (less material to dissipate heat). If my vibration returns too soon, I'll be going with slotted rotors from EBay: Click me

 

[weitekampt]

Maybe I need to clarify a bit more. Stock rotors WERE turned. Machined out good. The pulse isn't the "wobble" or slow pulse that is "normal signs of warping". This is a very rapid "buzz" almost that tingles your toes!

Still stumped. Brake jobs are so simple. I have done them on many other vehicles, but this dang thing always throws me for a curve ball!

 

[rdvit94]

I think I know what you are talking about. Does it almost feel like the pedal pushes back when you first hit the brakes? I had a similar problem with my truck, but after a while it just went away. Took it to Ford, and there couldn't find anything wrong /ubbthreads/images/graemlins/shrug.gif

 

[Bullet120]

I might be off base on this one. I've never taken the time to look at the abs sensor set up on these trucks. I know some use a sensor that reads the slots/fins in the rotor as it turns. Could something be in the rotor or on the sensor that would make it think the wheel isn't turning when you apply the brakes, causing the abs pulse?

 

[jonDIESEL]

NAPA has a lifetime replacement warranty on pads??? Is this the same for rotors??? Do you need to buy an additional plan? Interested...

 

[BadTrukRisin]

On my BMW, the slots on the rear wheels get filled up with road dirt and for a while I feel what he is talking about. Then later I will get the ABS light coming on and have to clean the sensor and brush out the slots in the wheel. Could be the same thing, don't know. /ubbthreads/images/graemlins/biggrin.gif
Bud

 

[weitekampt]

Well, if that is what the fins on the end of the rotors are for, then that may be the problem. They have been off the truck for over a year and were rusted pretty pad. The machining cleaned the surface obviously, but the "fins" were bad. Maybe I will just go in there and knock some rust off and see what happens.

Thanks for the idea. I just really feel it has something to do with the abs. It pulses so fast that it points me in that direction.

THANKS AGAIN!!!!

 

[AutoJim]

The 4WABS uses separate pulse wheels pressed onto the hub portion of the back of the front rotors and the RWSS in the top of the differential housing (with its pulse wheel attached to the ring gear/differential case) for input, not the internal vanes of the brake rotors, I'm afraid. It's not hard to pull the front WSSs and clean any "crud" off them. If you had the rotors replaced, make sure they used the front rotors with the pulse wheels (which are not available separately), not the RWABS front rotors that don't have the pulse wheels on them.

 

[weitekampt]

Cool, I'll check them out. Kind of hard to screw this thing up because they were the old front rotors from the factory. Just machined. But I will start going through the guts of this thing this weekend. Just annoying on the right foot if you know what I mean. Brakes just fine.

Thanks Jim!