I'm having an issue with my brakes. It was very intermittent, but seems to be happening a little more often lately. 99% of the time they work fine.

I'll try to describe. (vaguely) It will sometimes feel like the ABS is engaging, get a very hard pedal and some pulsing feeling. Sometimes just the pulsing without the hard pedal. It will happen at random times. Today it did it in the driveway going 5 MPH. No reason the ABS should think of kicking in.

I feel confident to rule out anything downstream at the wheels. I am leaning towards the master cylinder, but maybe that's wishful thinking. Afraid it also could be something sticking in the ABS which I assume is $$$.

Brake fluid is 18 months old with maybe 20k on it,

Thoughts anyone?

 

Sounds like something setting off the ABS.

 

I would have it scanned and see if it is giving any ABS codes..

 

Bigpipes: I have not dealt with this on my EX, but I have this exact problem with my Dodge Intrepid. Is this problem only occuring at low speeds (<10 mph) and most noticable when you are turning left or right coming to a stop? If yes, it is most likely one of your ABS sensors. You should have a sensor at each front hub. The ABS sensors read the speed of the rotation of "tone rings" (?? hopefully they are called a tone ring on an EX??). The ABS sensors start to fail (or the tone ring gets damaged) and it activates the abs system, and you can hear/feel the abs pulse kick in for a few seconds. Take a look and see if the abs sensors are still connected properly or if the tone ring is damaged. Good luck

 

Typical of an inconsistent reading from one of the three ABS sensors, one at each front wheel and one at the rear differential. The highest rate of failure on this trucks is first the rear sensor itself, often contaminated with too much iron wear particles. Sometimes they can be cleaned and work well, but mostly there is long tern damage to it and it needs to be replaced. The next highest issue tend to be the connection or wires to the rear sensor from the frame due to normal flexing.

Front sensors will also fail on high mileage vehicles, especially when the front hub bearings develop excessive clearance. If the front hubs appear good then new front sensors usually take care of the issue.

Replacing the rear sensor is often cheaper then getting it diagnosed, but I would first look at the rear connection and if you are good at checking wires for internal breaks do that before all else if you are over 150k miles.

Any faults in the M/C would not cause pulsing, only the ABS would do that. Usually a sensor that is on the edge of its useful life will cause the fault at a slow speed. If my truck, yeah I'd be buying a rear sensor and see if that takes care of it.

 

It will do it at various speeds and seemingly at random.

I had replaced the rear sensor last spring to fix a cruise control surging issue. I can't recall precisely when I first noticed it doing it, but probably at some point after the sensor change.

I'm not getting an ABS light, not sure if that means anything regarding potential codes.

2WD, the front wheel bearings I believe are fine...... I'll scrutinize them more closely when I pull the wheels to looks at sensors.

I was thinking MC just because of the way the pedal feels, but sensor or electrical issue perhaps makes more sense.

I'll give all the sensors and wiring a once over. Will report back once I fix it.

Always helps to get some other ideas and thinking.... thanks!

 

Intermittent problems are tough. Don't know enough about ABS to help but I might also suggest looking at your booster. Loss of vacuum will make the pedal very hard, and pulsing could be from the booster holding vacuum and releasing vacuum.

...just sayin'

 

The ABS light will come on once a certain threshold is reached.

Where did the rear sensor come from?

If one of the front sensors was acting like a wheel was skidding it would moderate the braking to that one front wheel only, so you also should be feeling some movement in the steering. If it's a rear sensor it reads off the ring gear tone wheel for both rear brakes, so both rear brakes would be moderated with no steering effect.

This vehicle has a close balance front to rear so if the rear (or both front) brakes are being modulated almost half of the brake effectiveness is withheld. It only should be for a short time, but that is dependent on the signal the controller is getting. The controller may also decide through its algorithm that the rear brakes should be proportioned down in pressure (ABS systems do this through the controller rather then the older method of using a physical proportioning valve.

Either of the above situations in a slow modulating mode will hold off fluid flow on part of the system making the pedal feel hard, just as it would with a malfunctioning booster, hydraulic or vacuum.

As you stated, I'd now check the rear connector and all wheel wires. The rear may be an issue since you had some rear issues before, but as I said I'd like to know where the sensor came from. It also might not hurt if you have the time to pull the rear sensor and see if the tips surface is covered with iron wear particles.

 

I found the sensor info in my email. Got it at Rock Auto last July and it's a Motorcraft. FWIW, it did fix my surging CC issue. (Speedo was also jumpy)

It did it again today on a stop from around 30 MPH. Wheel doesn't pull either way.

I tried some quick stops on grass today just to get the ABS to engage. The engagement on the grass felt a lot more subtle than what I am feeling when it does the odd pedal pulsation. Not sure what if anything that means. I'm not too familiar with normal ABS operation on this truck, never gets driven in snow.

I'll take the sensor out and look it over early next week. Thanks again......

 

Warped rotor

 

On chevies what happens is rust builds up under the ABS sensors and lifts them a bit so they can't see the tone ring all the time.

I would pull the front abs sensors, clean them, and file or scrape down the knuckle where the sensor sits. Check and make sure the wire connectors are clean and dry too.

 

I didn't look towards a rotor issue due to the combination of both a hard pedal with the pulsing. The one way without diagnostic equipment to sort out if this is related to the ABS or a combination of problems would be to pull the fuse(s) for the ABS and see if the problem continues.

 

Did you ever see Snooki and the gang?

 

Was that secret info...........not for us too?

 

I'm lost, what secret?