Brakes pulsate , steering wobbles like warped rotors ??? - Ford Powerstroke Diesel Forum
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Old 03-03-2013, 02:33 PM
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Exclamation Brakes pulsate , steering wobbles like warped rotors ???

2000 F350 7.3 SD Auto Crew Cab DWR 4WD.

After I start truck for the day, the 1st or 2nd time I apply brakes they work fine.

After that, every time I apply brakes, the pedal pulsates extremely hard, and the steering wheel will wobble left to right and back. You can feel the pulsation sitting as a passenger in the front or back seat. Mechanic at dealer said I had a warped rotor or rotors.

I had new rotors, calipers, pads installed. Brakes worked fine for about 30 times, then back to square 1. The same problem again. Dealer took everything off, turned rotors, installed another set of pads. Bled all the brake fluid out of system.

Brakes worked fine again for about 30 times and back to the same problem.

If I apply brakes easy, just a little pulsation, the harder I press the pedal the more extreme the pulsation. If I hit the brakes real hard, almost a lockup,
I get a hard pulsate, then stops pulsating within about 2-3 seconds and the truck stops. Start again and apply brakes and back to the pulsating.

Any Ideas before I shell out for another expensive replacement of rotors, calipers, pads that did not work the 1st time.

Thanks
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Old 03-03-2013, 03:54 PM
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Warped rotors is a myth (OK so there is some controversy in this so I'll say IMHO...)

Brake pulsations (IF this is your brakes) are about the slip/grab that happens because of the difference in the surface of the rotors braking area. That surface gets inconsistent and your brakes pulse as the rotor turns and exposes those differences to the pads (turning the rotor gives you a "fresh" surface and cures the issue but NOT because of any warp). You can actually prove this to yourself by taking pulsing rotors off and resurfacing them yourself with a DA sander.

So, that's why it's important to "Bed" the pads properly, that way it keeps the surface consistent, and it Stays consistent. What kind of pads are they? I'd change them before I'd change rotors again.

I assume, if you've had it to the Dealer, they've checked the Front End parts (BJ's - Tie rods - Hubs - etc.)
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Old 03-03-2013, 05:00 PM
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Do not know kind of pads as Dealer Installed.

Yes Sir, the front end was check out, everything was OK.

I understand what you are saying.

They put new rotors, Calipers and pads, left with the truck and still had the same problem the next day, brought the truck back the next day. They then took the rotors off and turned them, installed new pads, ( I guess the same pad type brand they had in inventory). Took the truck home and the next day still having the same problem. The Dealer is stumped has supposedly never seen this problem before.

Could they problem be coming from the Master Cylinder or the Power Boost? The last time I worked on a brake system was on a 57 Chevy many decades ago. I know the theory on braking is the same, however the components have changes a lot.

Thank you for your response.

Last edited by Stayloose47; 03-03-2013 at 05:04 PM.
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Old 03-03-2013, 05:11 PM
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I wonder if there's something going on with your ABS. The only times I feel any pulsating is during hard braking, which is the ABS keeping it from locking up.
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Old 03-04-2013, 02:01 AM
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Thank You for your reply.

Hmmm, I had not thought about the ABS. How ever you are correct in the way ABS functions.

After having a pot of coffee and giving serious thought, I think you are correct that this is the most likely thing to pursue at this time.

Slow Speeds 20 - 35
Apply brakes easy to slow down 3-5 mph, brakes work OK.
Apply brakes easy to complete stop, brakes work OK.
Hard panic stop, someone blew a stop sign, get strong pedal pulsation and steering wheel wobble varies 1/4 to 3/8 inch.

40 - 45
Apply brakes easy to slow down 3-5 mph, brakes OK.
Apply a little harder like a light change not a panic stop, get stronger pulsation in brake pedal and wobble in steering wheel back and forth varies 1/8 to 1/4 inch.
Hard panic stop, extreme pulsation in brake pedal and steering wheel wobble back and forth varies 1/4 to 3/8 inch.

50 - 55
Apply brakes easy to slow down for car pulling into my lane going 3-5 mph slower then I am. Brakes OK.

However if I reply brakes easy to slow down another 3 -5 mph a minute or two later I get light pedal pulsation and steering wheel wobble, back and forth varies 1/8 to 1/4 inch.

Apply brakes harder like a car cuts into your lane inches off your bumper stronger, pedal pulsation and steering wheel wobble 1/4 to 3/8 inch.


55 and Up
Above 50 and apply brakes easy 1 -2 seconds to slow down 3-5 mph get pedal pulsation and steering wheel wobble 1/4 to 3/8 inch.

Apply brakes harder 2 - 3 seconds like car cuts into your lane inches off your bumber pedal pulsation stronger, steering wheel wobble varies 3/8 to 5/8 inch.

Hard for panic stop, extreme pedal pulsation and steering wheel wobble, varies 3/8 to 3/4 inch.

The longer I have to apply the brakes, the stronger the pedal pulsation and steering wheel wobble. Pedal pulsation gets very strong. If you were to use your hand to apply pressure I would think the pedal would move back and forth 1/16 to 1/8 inch.

The steering wheel wobble will start out at 1/8 inch and continue to as much as 1 inch at 65 mph down to 40 mph when coming to a very quick stop.

Last edited by Stayloose47; 03-04-2013 at 02:18 AM.
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Old 03-04-2013, 06:10 AM
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And your sure none of this would happen in the "first 30 times"?

Also, seems like all that side-to-side wheel movement is weird (maybe I'm not remembering the last pulsing brakes I had right...).

I'd still be thinking this has something to do with the interaction of the pads and rotor changing (IF it doesn't happen at first). I would go to another pad, and bed them to the rotors right away. You want to smell them, even see a wisp of smoke from them, in a series of consecutive hard, but partial, stops from 50-5mph.

Instructions for bedding in your brakes
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Old 03-04-2013, 03:14 PM
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Sounds like you have death wobble caused by bad balljoint or tie rod then a brake problem. Google death wobble and see if that sounds like your issue.
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Old 03-04-2013, 03:35 PM
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Quote:
Originally Posted by UnlimitedLove View Post
Sounds like you have death wobble caused by bad balljoint or tie rod then a brake problem. Google death wobble and see if that sounds like your issue.
I think it would be extremely unlikely the Dealership would have missed any of that, especially when trying to resolve this problem they created...
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Old 03-04-2013, 04:08 PM
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Quote:
Originally Posted by NoRalPh View Post
I think it would be extremely unlikely the Dealership would have missed any of that, especially when trying to resolve this problem they created...
Bad unit bearings also.

True though, good point!
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