When Braking - Pulsating/Shaking

[J Ellsworth]

Ladies + Gents...



Usually I can figure this out without taking her to the dealer (mainly to save the $$)... but this time I need some help... Whenever I brake (it is worse at higher speeds obviously), the steering wheel shakes and it feels as if the brakes are pulsating (feels like the brakes are on, then off, then on etc).... so what I have done so far is - put on new rotors, new brake pads, rotated tires, front end alignment... nothing has fixed it yet... .... my next guess would be calipers or possibly bleed the brakes - but before I waste more time/money i figure I would ask you guys/gals first to save me the headache....



any ideas?



JE

 

[Gene Marshall]

Sounds like an anti-lock problem.

 

[Gene Marshall]

What Your Anti-Lock Brakes Do ABS can improve vehicle stability, steerability and stopping capability. Four-wheel ABS prevents wheel lock-up, allowing drivers to maintain stability as well as steering control during an emergency braking situation.



How the Anti-Lock Mechanism Works When a driver operating a four-wheel ABS equipped vehicle steps firmly on the brake pedal, the system automatically modulates the brake pressure at all four wheels, adjusting pressure to each wheel independently to prevent wheel lock-up. With four-wheel ABS, the driver has improved steering control of the vehicle.







The Difference Between Four-Wheel and Rear-Wheel Anti-Lock Brakes Four-wheel ABS is designed to maintain vehicle stability and improved steerability in emergency stopping situations. Because the braking system in a four-wheel anti-lock equipped vehicle modulates the braking pressure, preventing wheel lock on all four wheels, the driver has improved control over steering.



Rear-wheel anti-lock brakes, found exclusively on light trucks, vans and sports utility vehicles, prevent wheel lock of the rear wheels only. This allows the driver to maintain directional stability and prevents the rear end of the vehicle from skidding sideways. The front wheels can still lock up on rear-wheel ABS systems just like conventional brakes. If that happens, the driver should ease up on the brake pedal with just enough pressure to allow the front wheels to start rolling again, so the driver can steer.



How to Know when Your ABS Is Working Most anti-lock brakes let you know when you have activated your ABS. The driver can notice a mechanical sound and

feel some pulsation

or increased resistance in the brake pedal. It is important to keep your foot on the brake pedal when you hear noise or feel vibrations. Continue to apply firm pressure.

 

[Alan Peters]

Sounds like a warpped rotor, but if new if must be something with the ABS.

 

[J Ellsworth]

Al,

I thought it was the rotors too... thats why I bought new ones... but the problem is still there... I WISH it was the rotors...



I will have to look into the ABS...

 

[Richard L]

If you replaced the rotors, you may have the wrong rotors with the wrong tone-ring (ABS strobe) or knocked one of the ABS sensor out of alignment. The distance between the sensor and the tone ring on the rotor are critical to proper ABS operation. If the sensor is too far away or otherwise not detecting the spinning of the tone ring, the ABS system thinks that wheel is locked and skidding so it begins to pulse the brakes to prevent the wheel from locking up and skidding. It's also possible that the sensor wire or connector may have been damaged and you are not getting any signal from that sensor.



If you got the pulsing with the old rotors, and the new rotors, the sensor may have been hit by some road debris and was damaged or knocked out of alignment. Also, since the rear ABS sensor is located on top of the rear axle housing it would not easily be hit by anything, so my guess is that it's one of your front ABS sensors.



...Rich

 

[Mike Wilson]

Justin,

I see by your profile that you live in Connecticut. That is what the dealers and

manufacturers refer to as a High-Salt, Corrosion-Prone state, when they have to

give an excuse for a recall or tsb, to fix corrosion-related issues. There have

been several recalls and tsbs from different manufactures over the last 2-3

years for the issue that RichardL was referring to, as far as the abs sensor ring

or pick-up on the rotors. Corrosion and/or contamination from rust build-up on

the abs sensor ring and modulator, can cause problems similiar to what you are

describing, given that it seems you have replaced or serviced most everything

else, I would check further into this.

Keep us updated with the new info, and we will try to help you get into this

further, if necessary!

 

[Fudged Undies]

Warped Rotors.

 

[Richard L]

Spiff,

I would agree that pulsing shaking front end is cause by warped rotor, however JE indicated that he had the rotors replaced. Why would new rotors be warped?



Tracnblack,

I agree with you that corrosion would be a big factor in the Northeast where salt is used on the roads to removed snow and ice, however JE indicated that he replaced the rotors. New rotors would not be plagued with corrosion problems already. The sensors could be corroded, however when I looked at mine, they are all plastic so corrosion would not be an issue there either unless the metal mounting bracket had rusted and completely broke.



Most likely, it's corroded contacts in the electrical connections to the sensor/s. That would be something that would not easily be noticed during a quick visual brake inspection.



...Rich

 

[Todd Z]

Every set of new rotors I ever installed I always had a clean up passed because the way the parts place stores them they can warp , also if you buy the cheep ones you get what you pay for.

Another thing is did he heat them up during the break in period??.. this will warp new rotors also...



The front end should have been checked when the alignment was done..But most places don't check the lower ball joints properly...

I would say remove the rotors, Wire brush the hubs and the back of the rims... Can be a bunch of rust built ob in it causing something to sit crooked, Or when the rotors are off have a shop spin them on the brake lathe to check their truness....



BUT i see that the issue was there before the rotors where changed, So i lean towards it being a bad front end part....



Todd Z

 

[Yardsale]

Just going to toss-out some stuff ...



Ball joints?



Wheel bearings?



Tie rod ends?



It is possible that plastic sensor housings can become covered with road crud (I doubt it, but it's possible).

 

[Richard L]

Todd,

I have replaced many rotors and never, ever received a new "Warped" rotor. I don't see how the way the auto parts place stores them would cause them to warp?



The only thing that needs to be done to a new rotor is to clean them off with brake cleaner since they are often sprayed with a petroleum based protectant to prevent rusting.



I can assure you that it's almost impossible to warp new rotors on a street driven vehicle by not following a proper break-in procedure. The worst you will do is glaze the pads and the rotors. However overheating rotors after the wheels have been overtightened with a torque wrench can warp the rotors but they don't warp immediately. It will take a few thousand miles at minimum before the warping would cause a noticable shutter when braking.



...Rich

 

[Gavin Allan]

Sounds like warped rotors to me. Are you properly torquing down the lug nuts in the proper sequence and the proper torque value?

 

[J Ellsworth]

This started with my OLD rotors .. the pulsating... so i replaced them and the pads... the rotors are new and they arent the cheap ones (trust me)... i had the local shop check the rotors to make sure they weren't warped... and they were not... I am gonna dive back into it again this weekend and hopefully get some answers...



and the pulsating doesn't feel like ABS ... i know what that type of pulsating feels like.. this is alot more suttle.. but still there...



JE

 

[Richard L]

JE,

in your first post you said the steering wheel shakes. I don't consider that suttle.



It doesn't take but a minute to check and see if there is any visible problems with your ABS sensors, like broken wires or bent/broken mounting brackets, etc.



If you are convinced it's not the ABS and you have new rotors, then I can only suspect that there is something wrong with the rotors alignment but the question is what? I'm wondering if you lost a caliper mounting bolt, or the bolts are loose?



Anyway, let us know what they find. It might be interesting to take the truck to an independent repair shop and have them trouble shoot the problem. The Ford dealership may be assigning the same idiot rookie tech who did your brakes and he doesn't know how to diagnose the problem.



...Rich