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Pulsating brake pedal...I'm stumped

14K views 13 replies 5 participants last post by  The C Milk 
#1 ·
Hello everyone first time posting a question here, but have lurked the forums for a long time.
I have a 2002 F250 Lariat CCSB 5.4l.

let me start at the beginning,

My truck started to develop a shake in the dash and steering wheel a while ago. It would be worse some days but not as bad depending on how much I used my brakes. As soon as I would put pressure my brake pedal the dash would shake violently and my steering wheel would wobble. So I researched for a long time and found it was more likely to be bad "warped" rotors with hot spots on them causing the pads to grab better in some spots. I didn't think it would be ball joints because it would shake only during braking, I don't have any shake or wobbles any other time. My tires have about 20k on them balanced perfect and I have them rotated every oil change because they are a little more beefy than stock and I drive highway to and from work everyday.

So I pulled the wheels off and checked everything and they looked alright, pads looked ok, rotors seemed fine for an older, high mileage truck nothing noticeable. So I pushed the caliper piston back in a little to get them back together and decided to just go ahead and purchase new front rotors and pads just because I figured it could only help.

When I decided to replace the parts this past Sunday everything went smoothly nothing was to difficult to do and I didn't have any trouble getting the calipers off and brackets off. I greased the slide pins as the didn't slide that smooth, and pushed in the caliper piston (It did feel slightly tougher than what it should) replaced the rotors and pads, torqued everything to spec. Then put the wheels on and torqued those to spec and went to go and bed in the new rotors and pads.

Got out on the road and still had a bad shake/pulse in the steering wheel and pedal! I was stumped, so I did a 35 to 5-10 mild braking with a few 50 to 5-10 harder braking but still had the shake and pulse.

So I got home went inside to think and research for a while then decide to pull the rears off and check those out since it felt like the pulsating may be coming from the rear from the way the truck would slow down.

Got the rear wheels off and noticed the rotors were in tough shape. Tried pulling the calipers off, after a few hours of fighting each side I was able to free the calipers. Found out each caliper has a stuck piston, along with bad looking rotors, cracked and breaking pads. So I figured this is probably causing some problems haha.

So yesterday I bought all new rear rotors, calipers and pads and was ready to get the pulse out of my life!

Pulled everything apart, adjusted the emergency brake to make sure that would grab, put rotors on, put brackets on, put the new caliper on, then I bled the calipers until I felt they were good to go.

Took the truck for a drive.......and same damn thing, better stopping that's for sure, but still have a pulse and steering wheel shake. I also noticed a grinding noise in the front like a pad was just riding the rotor. So that leads me to believe those pistons on the front need a rebuild.

At this point I am going to rebuild the front calipers since the weren't completely stuck (and a o ring and dust boot are $7.99) to hopefully fix this issue.

Otherwise i'm all out of ideas, and money for now :laugh2:

any thoughts/help/conversation would be greatly appreciated. Thanks!
 
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#2 ·
I just went through this exact scenario. Mine ended up being a frozen u-joint. The rear joint by the pinion. What I suspect was happening was that when the brakes were applied, the axle shifted just enough to cause the frozen joint to shake the truck. New u- joints and my brake shudder went away...


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#4 ·
I have a 2WD, so I don't have the front joints, but I can see it being any of the driveshaft joints. I suppose the front shaft wouldn't be turning unless the hubs were locked. Mine was extremely obvious, but to test them, I would pull the shaft and check each joint for free range of motion and any play.


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#6 ·
Good plan I gave up on trying to reuse calipers I just get rebuilt ones when I do a brake job now makes life a lot easier.
DENNY
 
#7 · (Edited)
I installed new front calipers, bled them and torqued everything to spec....still a pulse in the pedal and wobble in the steering wheel. I'm stumped. I have a faint grinding/scraping noise from the driver side wheel.

I checked my u joints throughout the truck, none seemed to be loose stuck.

I'm completely lost at what is going on with my braking. It only shakes or wobbles or pulses during braking, no other time do I have this problem.

Edit: Spoke to a mechanic friend of mine who I used to work with, and he said try taking the front rotors and have them resurface them. He has had to send brand new ones back/resurfaced before. That would be his starting point without driving the truck. He said that is most likely where the problem is coming from because it is vibrating and pulsing in the pedal and steering wheel.
 
#8 ·
When you replaced the rotors, did you clean the hub faces where the rotors mount? I've seen issues where rust and dirt buildup can cause a lateral runout of the rotor, even when the wheel is torqued properly.

If you want to insure that all runout is out of the rotors, have them machined with an on car brake lathe. That takes into account runout of the rotor and hub as an assembly. If the rotor is turned off the vehicle, you might still have runout of the hub to deal with.
 
#10 ·
A wire brush should work. I use air tools with sanding discs on them when necessary to get the rust off. You want to get a smooth surface for the rotor to sit on.
 
#11 ·
Well popped off the front rotors and cleaned them off. They did have some build up on them, so I took the dremel with some sanding heads to it and all the surfaces it could reach. I even cleaned off where the caliper bracket mounts. Wire brushed around the studs and any other crevases that had any sort of build up in them.

Started out better (slight pulse and wobble) but by the end of my short run it was back to the usual pulse in the pedal and steering wheel shake. It seems that as the rotor gets hotter it gets worse?

I also had the rotor hand tightened on and hand tightned the lug nuts on without the wheel to hold it and spin it. I looked through the caliper and watched it spin and it looked like it had a slight change in thickness around the rotor. Its not the most precise way to tell but it did seem different. Also as I would spin the rotor by hand it would have a slight drag on one side and not the other.

On a positive note my little squeak/grind on the driver side brake is gone now.
 
#12 ·
Do you have a dial caliper? Look up rotor indexing on YouTube.


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#13 ·
Bad bearing?

I've read somewhere that a bad front bearing in the hub assy on a 4 wheel drive, will allow the hub to wobble a bit, and when braking, will cause the pedal to pulsate. You have a noise in one front wheel anyway, I'd look for a bad hub assy bearing.
 
#14 ·
I found the problem!

Bad (new) front right rotor, I felt a slight drag while freely spinning the rotor after putting the caliper back on. So I put on an old rotor, the better of the two, torqued everything back down. Took it for a ride and the pulse and wobble are gone.
 
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