Quick background, 2006 Mustang GT, manual with 2300 miles.

This started up about a week ago. The first time I noticed it was braking from about 40ish on a normal road. It hard to describe, but almost felt like something slipped in the brakes or moved.

After that I have noticed a very slight and light feeling bumpiness in the pedals in general. This happens when moving whether driving with engine on or coasting with engine off. It's not huge feeling, although noticable, but it's not smooth like it was or like every other car I have ever driven. I'm not mr. mechanic, but I did check my tire pressure. And that's why I tried with engine off coasting and braking to see if I got the same thing without engine/muffler noise factors, which I did. Maybe loose brake caliper? I dunno.

I've had a couple more times when it felt like something "slipped" during braking again as well. I will be taking it in to the shop on Monday or Tuesday, so I was hoping for input from someone who this makes a little sense too.

 

I think I may be having the same issue you described. It almost feels like the ABS is engaging, but for me it has happened only under (very) light braking pressure, so I don't think that is it. I hadn't been too worried about it in the past because it rarely crops up and doesn't seem to be a big problem. Please let me know what the dealer says about it.

-TRB

 

I made the appointment today before I left work for Monday 7am. Until then, I'm just gonna drive it to and from work and maybe to the store this weekend unless something unexpected comes up. As I drove home today, I kinda came to the conclusion that the sensation in the pedal is most evident when light braking on a slight turn especially to the right.

I'll definately post what I find out, even if they just tell me I'm insane and have sensative feet.

 

Caution-
if you think it MIGHT be the ABS, get it checked out...when my wifes windstar was almost new, a several times ABS came on during dry/normal stops, usually on bumpy roads. twice abs fault light came on, after hitting a bump...figured to have it looked at following week when in for first service...well, one day at about 25 mph I almost rearended a car after hitting a small bump while braking- abs kicked in and car too forever to stop, guess it had a loose sensor in one front wheel, and it 'thought' it was skidding. They found the problem and fixed it in no time, but I'd never have expected ABS might cause reduced braking power in any failure mode...that was 70,000 miles ago- while not my favorite car, gotta say so far its been very reliable...fuel pump at 6k, the ABS thing, and a stuck wheel cylinder in 8 years- not too shabby..

 

95% of the time you can feel vibration in the pedal is from either a slightly warped rotor or tire out of balance. You have a hydraulic connection to the brakes, the ONLY thing that will cause the pedal to surge is changes in that pressure.

 

I was thinking along the same lines too. Rather early for that, but anything is possible. Or caused by over tourqed lug nuts.

 

UPDATE:

I took it to the shop Jan 16th, and they could not find anything wrong. Said they test drove it, and everything seemed was ok. They had checked TSBs and called Ford to see if there was anything out there. Fast forward through the past 15 days I could stll feel this bumpiness when braking. It's always there now on some level. Espacially bad at moderate to hard braking. Example, a stop light changes to yellow, and you have to brake from 45 to 0 or risk running through a possible red light with a cop on the corner. So you brake and have to brake moderately quickly, and not a power brake mind you like if a kid runs out in front of your car, but as you step on down it feels like a heavy bump, bump, bump, bump as you are stopping. You feel this in the pedals, seat and floorboard, and the car doesn't seem to stop as quickly as it should. Every car I have ever had when you applied brakes, whether hard, medium or soft, it was a smooth feeling coming to a stop.

This car just does not feel the same as it did for the first 2000 miles. Something is just not right here, I have another appointment Monday at 7:30am with a dealer. I'm going to take my service advisor on a quick drive before I leave the shop to make sure they know what I'm talking about this time out. There is really no confidence of my car stopping in a emergency situation the way things are now. This can't be a normal thing, if it is then I'm going to have to get rid of it as much as it would kill me.

I'll have them check the lugs, alignment and rotors and cross my fingers.

 

if i was you i would find another way to get around...i would not drive the car...i would even have it towed to the dealer....the risk is way to high....

 

I hear ya, I've already decided to keep her parked until Monday. It's gonna be a long, long, long weekend at home. God help me.

 

Well if I drove it I could probably tell you in 10 sec what it is. If its the pedal surging and usually a little wheel vibration under braking its probably warped rotors. If you feel that its 'slipping' like actually loosing brake power and extending your stops and you feel fast vibration in the pedal too, its probably the abs. A loose or broken caliper mount will usually have a large thunk every time you touch the brake pedal.

Still sounds like a warped rotor to me though. If you are coasting very slow, you can also fell the slight uneven grab/release/grab sensation with very light pedal pressure.

 

What would cause a rotor to warp like that? It was fine for the first 2000 miles, then outta the blue this starts.

 

Im with kevin on this.


What can cause it usually is heating up the rotors by aggressive stops in a row. Heating up the rotors and quicky cooled down with a puddle, or a car wash. Over torqued lug nuts, bad caliper hanging up. And probly a few more that I cant think of right now.

 

Sometimes it just happens, like the metals are not 100% consistant. A little bit of stress heat causes the rotor to get a little out of whack. And yes, a deep puddle on hot brakes, or spraying them down to wash the car right after a long drive can do it too. Usually the problem goes away after they turn them true. There are cars with 0 miles on them that need a rotor turned, right off the truck. If that is what it is then its really not a big deal, although the car will drive you nuts to drive it. It only needs the slightest warp to feel like its got the Flintstone's brakes.

Usually its not the lugs on rwd cars, the rotor is part of the hub on the front and the rear is quite heavy duty on a mustang. FWD cars with tiny floating rotors(especially japanese cars with little tea coasters on the back) can easilly warp the rear rotors by torquing the lugs unevenly. Heck even the V6 has vented rear rotors on the base model, when you ask why Honda can give you breakaway mirrors on a car, look at what they give you for brakes sometime.

 

it sounds as if you have a pulsation in the pedal due to "warped rotors"...they're not really warped but it's the term usually applied to this condition. unfortunately, once the pulsation is felt, the rotors must be turned. they DO NOT have to be replaced. i have rotors on my caddy with over 50k miles on them and just had them turned a second time...they had plenty of meat left on them, that allowed them to be turned rather than replaced.

now here's the important part: once your rotors are turned (you can retain the same pads, they don't have to replaced because of the pulsation) you must bed in the pads to the rotors. this is critical on ALL cars including new ones. without doing this procedure you will surely warp the rotors once again. google "bedding in brake pads" and you will find a host of articles describing the process. it's a little scary at times but it's also kinda fun, just pick a time of day and a road less traveled and about a 1/2 hour..the cool down process is very important to the procedure.

an interesting aside: this is such a common problem with rotors that some dealerships (mine for example) and brake shops will go through a bedding in process while the car is on the lift, using a machine. the advantage is no road test is necessary and of course, keeps the cost down to the consumer.

anyone having their brakes done should query the shop to find out if the bedding of the brakes is being done...if not, then have fun!!
jackg 90seville 99k

 

What type of problem would this be with the ABS? Is soemthing going bad or just not working correctly?

 

If the ABS was going into anti-lock prematurely it would pulsate just as if it were on ice even if it were well within the gripping power of the brakes. I have never seen that happen myself though. ABS is pretty darn reliable. Just trying to help him describe the issue in more detail. He was worried about something that is most likely a nusiance rather then some dangerous problem. He never answered as to what the fix/problem was yet. Still betting on the rotors.

 

We get a few cars in now and then that the abs is activating when it shouldnt be. And its darn scary.