I have a 98 that I just installed braided lines, new calipers, new pads and had the rotors turned (they were new about 15,000 miles ago) on the front. The back drums were untouched. I have ABS on the front BTW. I have bled about 1/2 gallon of fluid, and when I brake, the pedal pulsates. I keep bleeding them thinking maybe because of ABS it needs a little extra, but it doesn't seem to be getting any better. I spoke to a mechanic friend who said to try bleeding the whole system back & front. Any suggestions? Thanks in advance...


AMMOEATER

 

You probably have a problem with one of the sensors/rings on one of the front wheels. Is it possible the rings were bent when the rotors where turned?

 

Just a thaught, but maybe there is air in the lines after bleeding? Not uncommon really, but try it again maybe.

 

When the pedal pulsates do you hear the ABS pump run? If you don't, you should be able to rule out the ABS. If the steering wheel shakes at the same time, then it is the front. I can't see how air in the system would cause a pulsation. It would/should cause a low pedal though. My guess is that the rotors were improperly mounted when they turned and now have run out addedto them. The other thing I see is when tire shine, grease, or oil gets on the rotors in one spot, that it will make the brakes grab and then slip when it passes over the dirty spot.

 

Thanks for the responses guys. I took it out and jumped on the brakes a little to maybe purge the air out of the ABS. I am going to bleed the whole system, front & rear, and hopefully that is going to do it. If not, I guess I'll try new rotors...I'll let you know, thanks again.

AMMOEATER

 

OK, I am fed up. I bled it again, took it out and it is the same. I tried pulling the fuse for the ABS, and the pedal still jumps around when you get on the brakes. It seems to vary according to speed, too. What should my next step be, new rotors? The new calipers were Autozone remans, could I have gotten a dud? Advice is appreciated, don't want to keep throwing money at it...


AMMOEATER

 

Unless your bleeding procedure is flawed (and I'm not saying it is) it sounds as if you've eliminated that possibility, one thing though - most vehicles these days have dual-circuit braking (I'm assuming F-150 has this setup) which works diagonally- so if a brake line goes out, the other circuit still works, you get one front wheel and the opposite back wheel, in order to still brake reasonably evenly...point is, if you didn't bleed the rear, you didn't bleed the system....

How is your wheel bearing tension?

Another thought, I've never noticed any feeling when braking in an ABS vehicle, but essentially ABS pulses your brakes on and off to prevent lockup - like pumping the brakes. Is it possible to feel something from the ABS working? Not that it sounds as if that's what you're getting.

 

I don't know about the bearing tension, but I pulled the fuse for the ABS which should have disabled it according to another thread I saw. It still pulsed, so I am assuming it is not an ABS problem?

AMMOEATER

 

From what you've written, you had the rotors done and you've fitted them yourself? Depending on model etc (I'm new to the F-150) your wheel bearings will be a traditional assembly or possibly sealed units pressed into your rotors and essentially non-adjustable/repackable.

Whether it's the former or latter, the retaining nuts need to be torqued appropriately, loose nuts can cause shimmy, most noticeable when braking and such. Please don't be offended if I'm asking a basic question (as it sounds as if you're experienced) but since you didn't mention this aspect of the assembly, maybe it's worth checking.

I guess for that matter, it's worth retracing your steps and making sure that everything went back in the way it came out. It may also be that anti-squeal/anti-shudder compound is required on the back of the pads, it's usually an orange silicone compound....but the vibration you describe sounds extreme...

 

LIKE I SAID BEFORE I've never seen air in a brake system that cause apulsation(I've been a Ford tech for 16 years). Wheel bearings that were loose could cause some looseness in the steering, but I doubt that they would cause a brake pulsation. I HAVE seen rotors that were turned with an off car lathe cause a pulsation. It sounds like the guy who turned your rotors didn't turn them straight or your hubs are distorted and have, too much runout. If you want to correctly check your rotors, remove your front wheel, reinstall your lug nuts and torque. Take a dial indicator and check the run out of the rotor face. I would say anything over .005 is bad and you need to turn the rotors with a ON-CAR lathe or replace your rotors. The other thing is that if you rammed your lug nuts on with an impact you can distort the rotor and cause a pulsation. Eliminate your ROTORS first before you waste anymore time or money.

 

dwsf150,

You are right . I took my rotors to a friend's garage and they re-turned them for me. Said he's had 4 people come in with the same problem, and we all had them turned at the same Conway Auto in town...Either their lathe is off or someone doesn't know how to run it. Back on and good as new! Thanks everybody for the replies, and thanks dwsf150 for saving me some dough!

AMMOEATER

 

have ur backs adjusted. when your front pads get thinner the rears adjust auto. but so tech when u push the pedal down ur pushing slightly farther on worn pads then u would on new. so your rears adjust for it. well when you go back to front pads you rears dont adjust back. so you have to adjust them. what your really doing is making your fronts work harder since your rear arent engaging when they should be so your front is taking more abuse. this can ruin new rotors and pads by over heating them if ur hard on brakes ( i live in duluth mn a very steep hill city) personally i dont kno how to adjust i can find out tho. i work at sears which is a 15.99 for a brake eval and if u have any work done the eval cost is deleted and the work/labor is the charge (which gives u the eval free) to adjust and clean the rear which im sure they will tell u that u need from what u descibe is a $20 maintance service. so 20 bux to fix the problem.