1994 XLT Brake Problem

[GGhostrider1]

Hey everyone,

I couple months ago I did a slight overhaul on my brake system. I replaced the front rotors, calipers, slide pins, and pads, on both wheels. I also readjusted the drum brakes in the back. After doing all of this I bled the entire system. I drove it around and it worked well and everything was good.

Recently my parking brake light came on while I was driving (indicating low brake fluid). Being stupid me I did not immediately stop and add more fluid and I waited a few days to add more fluid. Now when I am coming to a stop my brake pedal pulsates/locks up and it sounds like the ABS is kicking it or something weird. This happens at 5mph almost every time that I am coming to a stop. I re-bled the system but it is continuing to do it.

I am wondering if it is possible that when the master cylinder went dry that it got air into the Hydraulic Control Unit and that this is what would be causing this problem or if it something else entirely, any suggestions/solutions would be great!

Thanks

 

[JohnJ]

Check for a fluid leak, especially at the connection hose to caliper, at each of four bleeders, and around the caliper pistons (leaking onto inboard pad).

 

[MaciekPL87]

Mine has been doing the exact same thing, I have some rust buildup right under the master on the booster but mechanic said it's still good. The booster had some seep of brake fluid on it but it has stopped.... after bleeding system it seems to have stopped leaking (I don't know what happened). Now only one every couple of weeks I get a "half" ABS pump when slowing down. I know what you mean, it is a bad feeling when you're slowing down for traffic and you're break pedal doesn't want to listen to your foot.... Check the booster, I have a friend who lost his breaks in his Limited because of rusted out booster and a bad master cylinder leaking fluid into the boost, he crashed...

Makes me wonder why I still haven't changed my damn booster...

 

[JohnJ]

Because for the price of a booster you could buy spaghetti for lunch for two days? Seriously, though, driving around with your master leaking fluid into the booster is about as safe as driving around with the front joint of your rear driveshaft making thumping noises.

 

[GGhostrider1]

I have no leaking around the calipers or near the rear drums... I am not losing fluid and the booster appears to be in good condition so I am not sure what the deal is.... Maybe I will just take it in.

 

[Explodr94]

Did you un-hook the battery when you bled the system? If not you may have confused the ABS sensor. Try disconnecting the battery and bleed again.

 

[JohnJ]

After rereading the OP I am reminded of a similar description of a thing that happens with a lot of full sized GM trucks with the front wheel speed sensors located inside the hub/bearing assembly. It's common enough that they issued a recall wherein they coat the tone ring with WD-40 and put wheel bearing grease on the ABS sensor unless the sensor is physically deformed in which case the sensor is replaced. I realize your 94 Explorer isn't a full size GM, but still, it's worth considering whether you might have a similar issue.

What happens with these is that corrosion develops which can get caught in the gaps of the tone ring causing a poor effect or crush the sensor increasing the air gap. In either case, the wheel speed sensor give a slightly erroneaous signal.

The effect of this bad signal is that the brakes including ABS work normally until very low speed (say 15 to 5 MPH) at which time the wheel speed at one wheel is read as 0. The ABS sees this as a lockup which it responds to by pulsing and reducing overall braking so suddenly you hear a buzz and it can take easily 200 feet to bleed of that last few MPH for a complete stop. Also, the brake pedal may jerk slightly up and down.

If this sounds like a similar effect to what you are experiencing, it might be a good idea to check your ABS sensors and also look for excessive amounts of metal particulate in the rear differential oil.