Low speed braking issue

[nadthomas]

I have an 02 Sport that has developed an odd braking issue recently. Under normal to light braking just before coming to a stop the brake pedal will go soft and kind of pulse, almost like the ABS is kicking in. Applying more pressure to the pedal when this happens brings it to a stop no problem. When doing moderate to hard braking(short of engaging ABS) this doesn't happen at all and the stops exactly as expected.

I only drive it about once or twice per week so it does sit a good amount. Its going to become an off road toy soon.

I'm still pretty new to the Explorer so any help/ideas are appreciated.

 

[deweyville65]

I have an 02 Sport that has developed an odd braking issue recently. Under normal to light braking just before coming to a stop the brake pedal will go soft and kind of pulse, almost like the ABS is kicking in. Applying more pressure to the pedal when this happens brings it to a stop no problem. When doing moderate to hard braking(short of engaging ABS) this doesn't happen at all and the stops exactly as expected.

I only drive it about once or twice per week so it does sit a good amount. Its going to become an off road toy soon.

I'm still pretty new to the Explorer so any help/ideas are appreciated.

Calipers may be sticking, more noticeable at low speed with lighter pressure. You may need to pull the calipers and lube the pins and guides

 

[nadthomas]

I wouldn't think the caliper sticking would cause the pedal to go soft. I would think that the pedal would feel the same(or firmer), and just that it was not stopping. Thanks for the input though, I do plan to take them apart and do some basic maintenance, but I suspect there is something more going on here.

 

[koda2000]

I wouldn't think the caliper sticking would cause the pedal to go soft. I would think that the pedal would feel the same(or firmer), and just that it was not stopping. Thanks for the input though, I do plan to take them apart and do some basic maintenance, but I suspect there is something more going on here.

i agree. sticking calipers can cause pulling and even vibration and pedal pluse, but it doesn't explain the pedal going soft. the only reason this might happen is the seals in the master cylinder leaking internally, or brake fluid with a lot of moister in it boiling, which doesn't sound like your problem.

 

[nadthomas]

i agree. sticking calipers can cause pulling and even vibration and pedal pluse, but it doesn't explain the pedal going soft. the only reason this might happen is the seals in the master cylinder leaking internally, or brake fluid with a lot of moister in it boiling, which doesn't sound like your problem.

Yeah, its certainly not boiled fluid. This can happen at the very first stop sign 100 yards from my house under normal braking, but if I go hard on the brakes at the next stop sign a 1/4 mile down the round no issues. The only thing that is consistent is that it must be normal to light brake pressure under 5mph. Like when pulling into a parking space.

If the seals in the master cylinder were leaking wouldn't I also see a loss of fluid? Maybe not on the ground, but at least a drop in the brake fluid level. Although, I'll be honest I'm not 100% certain on the internal workings of the master cylinder so, I could be thinking incorrectly. Regardless the fluid level has been solid for the year I have owned it.

I do plan to flush the fluid as well. I just trying to narrow down a solid culprit with hopefully replacement parts in hand while I have it all apparent for inspection/maintenance.

 

[Dave 1955]

It is the abs system kicking in prolly.
Did it on my 95 now and then till I replaced the front bearings..but I would get a abs light sometimes do you?

 

[koda2000]

Yeah, its certainly not boiled fluid. This can happen at the very first stop sign 100 yards from my house under normal braking, but if I go hard on the brakes at the next stop sign a 1/4 mile down the round no issues. The only thing that is consistent is that it must be normal to light brake pressure under 5mph. Like when pulling into a parking space.

If the seals in the master cylinder were leaking wouldn't I also see a loss of fluid? Maybe not on the ground, but at least a drop in the brake fluid level. Although, I'll be honest I'm not 100% certain on the internal workings of the master cylinder so, I could be thinking incorrectly. Regardless the fluid level has been solid for the year I have owned it.

I do plan to flush the fluid as well. I just trying to narrow down a solid culprit with hopefully replacement parts in hand while I have it all apparent for inspection/maintenance.

if the seals inside the master cylinder are leaking, you would not see any loose of fluid or external wetness. just a soft pedal.

 

[bill06447]

Try cleaning the rusty ABS pickup rings. Common problem on Trailblazers and such, which GM addresses in a bulletin, can't see how it could be any different on our trucks...

Bill

 

[nadthomas]

Try cleaning the rusty ABS pickup rings. Common problem on Trailblazers and such, which GM addresses in a bulletin, can't see how it could be any different on our trucks...

Bill

Thanks. I had read a post on here of someone doing the same, although their issue wasn't exactly the same as mine. So, I do plan to do that as well. Also for those that asked I did not get an ABS light on the dash when this happens.

I think I will just clean, re-grease, and flush everything and if that fixes anything. If that does not address the issue then I will probably start with replacing the master cylinder. Hopefully, that is not a painful job to do.

 

[koda2000]

as i said, the soft/low pedal can only be master cylinder related. it isn't very hard to change, just make sure you bench bleed all the air out of it before installing. the low speed braking issue may very well be ABS related.

 

[deweyville65]

FWIW. My 96 has a soft pedal also. Stops smooth and straight every time. If I have to stop rather quickly, it stops with authority, but the pedal is lower than one would be used to in another vehicle. i attribute mine to old fluid in the front system. I have vacuumed the fluid out of both rear calipers until getting fresh fluid. The fronts are a different story. The bleeder screws are frozen in the calipers, so the fluid hasn't been changed in the front. That will be the next project. New calipers and pads, maybe rotors too, if needed. The only time my ABS has activated is in snow and ice.Mine has been doing this for 2 1/2 years. Like I said FWIW

 

[koda2000]

FWIW. My 96 has a soft pedal also. Stops smooth and straight every time. If I have to stop rather quickly, it stops with authority, but the pedal is lower than one would be used to in another vehicle. i attribute mine to old fluid in the front system. I have vacuumed the fluid out of both rear calipers until getting fresh fluid. The fronts are a different story. The bleeder screws are frozen in the calipers, so the fluid hasn't been changed in the front. That will be the next project. New calipers and pads, maybe rotors too, if needed. The only time my ABS has activated is in snow and ice.Mine has been doing this for 2 1/2 years. Like I said FWIW

you might also want to consider changing the front flex lines. old rubber lines can get soft and the added expansion can soften the pedal feel.

 

[bill06447]

Also, make sure the caliper slide pins are free. If not, one pad (usually the inboard one) will wear first and since the slides don't move to compensate for wear the pedal will be low.

Bill