I have an intermittent brake problem on my 1999 Durango SLT, 5.2 with abs, no sensors on hubs. Sometimes, when I am stopping the brakes do not apply fully. It feels like they are on the release cycle of the abs. I can feel them applying then they back off and eventually they work fine. They are still stopping, but at about 1/4-1/2 of normal braking.

There is no pattern when this is going to happen. I can be hitting them hard or normally. Everything is pretty new up front, pins, pads, piston seals. The calipers are a couple of years old. I flush and change the brake fluid about every other year.

 

Check your fluid level and look around for leaks... if all is good then i would try bleeding the out again... sounds like there is either a leak somewhere or air in the system.

 

No leaks. I thought there might be air in the system and I've bled the brakes several times with a pressure bleeder and with a helper pressing the brakes. I've read where the abs units need to be pulsed while bleeding. Is there any special pulse pattern or do they just need to be pulsed?

I focus on the abs because sometimes if you are braking and hit a bump the brakes will let off a little.

I have some relays that I can pulse using 555 timers and a few resistors. I can pulse them in any pattern with variable delays if needed. LOL

 

the abs module only needs to be cycled if air gets into it,

also in order to cycle it you need a drbIII scantool

 

We've had a foot of snow and they haven't given me a problem. The abs even seems to work fine when I lock the brakes up on ice. Beats the hell out of me.

The abs block just has a couple of solenoids that trip on 12V. So you only have to connect up to your own relays and you can cycle them. I don't know if there is some order or pattern that is best to cycle them.

 

Well, if you want to know if it is an ABS problem or not, simply unplug the ABS unit, or pull the Fuse. If the pedal still sinks with ABS disabled, your problem is something else.

Maybe you have a bad Master Cylinder.