Got another problem to run past you guys. When I hit the brakes the pedal goes down like normal then begins to pulsate. But the best part is that I have very little stopping power at this point. There is also a chattering noise which sounds like the abs kicking in. Could this be a bad master cylinder? Has only happened a couple of times so far. But thats a couple times too many.

I checked autozone for Master Cylinder. How do I know if I have speed control does that mean cruise or speed controled abs (RABS)

 

You have one or more warp rotors. The high an low spots of the warped rotor(s) are what is giving you that pulsation in the pedal.

 

If that were the case wouldn't it pulse all the time. This has happened twice in the past month. Once a few weeks ago and once today.

 

Your pads don't come in contact with your rotors until you push on the pedal. Mine did that so I replaced them. I went to steel Baer rotors. If you don't want to spend the money then a good aftermarket replacement is available. What happens is the rotors heat up and if you get them wet it cools them too quickly and they warp.

 

You guys aren't understanding my problem. I know that it's not the rotors. If it were the rotors the steering wheel would shimmy when I brake at highway speed. That is not the case. When this Happens it's like I have no brakes, no matter how hard I press the pedal I do not stop any quicker. Both times it's happened it's been less than 1200 ft from my house so the brakes were not hot either. Both times it's happened there is that very familiar chatter of anti lock brakes. Could it possibly be that failing?

 

Shimmy comes from loose/worn steering components. You haven't said if it's 2w or 4w drive and the mileage. With the chattering of the abs coming on it sounds like you don't have the brakin power you should. It's like the pads are worn out of the master cylinder isn't puttinf out the needed pressure. If it's the calipers it's usually just one and that causes it to pull to one side or the other. It could be a frozen caliper that you feel the brake pedal but it's not moving. Pressure in but no output.

 

Look under the vehicle at each wheel for signs of any wetness. If one of the calipers is leaking brake fluid, that wheel will try to lockup when you apply the brakes. The ABS will kick in and try to keep that wheel from locking up. The pulsation you're referring to might be the ABS pump applying and releasing pressure to that one wheel.

As you drive, any residue brake fluid will eventually be wiped or burnt off and the problem will diminish as you drive. This would also make the problem most prevalent if the vehicle has sat for a while, like overnight.

 

Sorry, it's a `97 expy 4x4 w/140k miles.

My original thought was that the M.cylinder was going bad because there is still plenty of hard pedal. And they are usually a hit and miss problem, but the thing that baffeled me was the chattering. I am in no way a stranger to Ford vehicles. I've replaced M. cylinders on 3 other trucks in the past but they were all pre-ABS. There isn't an idiot light on so the ABS control module thinks it's okay. Is this what happens with the "new" system when the M. cylinder goes out?

 

does it only do it bellow 10 mph? Mine did the same thing and it was a ABS sensor.

Dave

 

yes as a matter of fact both times it happened I as I was coasting to a stop. How much did that set you back?

 

That, and are all your tires the same size? And one is not seriously underinflated?

(Duh - do the '97s have 4WABS with sensors at all four corners, or does the ABS use the sensor in the diff to monitor the rear wheels?)

 

The 97 uses the abs sensor on the differental, there is not a seperate one on each rear wheel. There is a seperate one on each front wheel.

 

Can I disconnect the sensor to make the problem go away until I can get it fixed? I know that the idiot light will probably come on, but I'd rather see a light on the dash than rearend somebody or cruise though a red light!!!