Brakes weak in quick-stop situations.

[Vitos9th]

Hello, I've got a question about my moms '96 5.0 Explorer. She recently said the brakes didn't feel quite right so I drove it and under normal conditions (light braking for stop signs/lights, city driving, etc.) they felt great. But, when I would make "quick" or "panic" stops, it would take a while to stop. I decided to have a look so I pulled the wheels off to give the brakes a nice inspection. Visually, everything checked out, plenty of pad left (4-wheel disc), brake lines look good, no leaks, nothing seemed broken or anything.
Next, I checked the brake fluid, it was a little low but nothing extreme. I added fluid, and decided to bleed the brakes anyway. After all this, I netted the same result.
Next, I tested the parking brake booster according to my Haynes manual and it seems to be airtight.
Next I flushed the brake fluid since it looked old, same result.
My dad, convinced it was the master cylinder, wanted to replace it. I picked it up, bench-bled it, installed it, and low and behold....brakes feel exactly the same!
I'm at a loss at this point, though i service/replace my own brakes when needed with good results, I'm no expert on the brake system.
Could the ABS be kicking in a little too liberally? a sensor or something else I can check? Again, under "normal" or "light to medium" use the brakes feel fine, but when I hit 'em hard the car just travels pretty darn far.
Ok one more thing, I know the post is long, sorry: Another thing I noticed is when I have my foot on the brake, then start it up, the pedal softens, as it should, but then there is like a pop or jarring feeling in the pedal, that's the best I can describe it, it happens and then thats it.
So, any ideas anybody? What am I missing here?? Thanks!

 

[joecrna]

I take it she has been driving this vehicle for some time. If so, I can't think of anything but cleaning the rotor and disc surfaces with a good spray of brake cleaner in case they picked up some contamination somewhere. If she hasn't used them hard like this before, remember that Explorers have notoriously weak brakes. Add a set of larger tires and they may not even be able to induce ABS on a decent surface.

Sorry I don't have better info for you.

 

[Vitos9th]

She's the second owner but yea its got a lot of miles, i forget the number but more than my first-gen (162,000). She pretty much does city driving, thats about it.
Yeah I think I'm going to re-inspect and also give all the rotors, etc. a good cleaning, might as well grease the caliper bolts too.
Thanks for your response, as I keep troubleshooting this I'll update the thread. Thanks!

 

[Vitos9th]

Didn't know they had that the 2nd-gens had that kind of notoriety for the weak brakes, but that IS why I am contemplating an upgrade on my 92; not sure if I will but I am researching converting to 4-wheel disc, hate those drums! But that's another story and more money.

 

[my98nnj]

The initial bite is all related to the pads. A nice grabby organic pad will yield you a quick panic stop, where as a ceramic or metallic pad will need to heat up before it grabs. (some more so then others)

Although your pads and rotors look good, I would suggest you change the pads to get your panic stop back to what might feel better for you. Research the pad you choose before you purchase it. Google is your friend!

 

[gc67]

Might want to check the hoses and lines. If the hoses need to be replaced and are expanding under pressure, it could cause that issue. I would also check your Haynes manual's trouble shooting section. They usually are a good starting point for figuring out issues like this

 

[Vitos9th]

yeah I checked the haynes manual and double checked the few things it mentioned. I rechecked everything, taking the calipers off so I could get a nice close look at the pads and rotors and the rotors seem fine, and the pads are good but are literally right at the sensor point, so instead of waiting a couple months I replaced all the pads.
Unfortunately I had to replace the parking brake shoes since they were falling apart, which was such a pain but I shouldn't ever have to do it again to her car now.
So I replaced all the pads, cleaned everything up, and the same damn thing. I checked the lines/hoses again and they all look to be in good condition, no significant wear, weathering, cracks, or anything like that.
It's definitely a bummer that I haven't found the cause yet. On the good side, they don't feel terrible, just not 100%, so I'll have to get back to it next week, since I'm going out of town tomorrow. Thanks for your comments guys, I'll be posting when I have updates on this.

 

[Vitos9th]

@ My98nnj, yea I looked into some different pad options between organic semi-metallic and ceramic. I decided to go with the Wagner Quick-Stop semi-metallics since they'll have longer pad life than the organics. I understand what your saying about the panic stop being better on the organics, but since I've used semi-metallic Wagners before on my and her car, I'm still surprised with the feel I'm getting. I think this weekend away will be nice, so I'll come back to it with a fresh mind and maybe some new ideas.

 

[gmanpaint]

Might want to check the hoses and lines. If the hoses need to be replaced and are expanding under pressure, it could cause that issue. I would also check your Haynes manual's trouble shooting section. They usually are a good starting point for figuring out issues like this

Bingo!
If everything else is confirmed in good working order, the front lines is the 1st thing I would replace, AND flush the entire system with new fresh fluids. Old fluids will act like a bad Master as well. Air bubbles trapped will also result in a soft peddle.

I see you did replace the fluids, but It doesn't hurt to flush it again with DOT 3.

 

[my98nnj]

I'm currently running the Wagners as well, they seem fine. I used to run the Wagners on my Maxima and was never happy with the brakes. I switched the Maxima over to Hawk HPS and the difference in breaking was night and day.

The Explorer is heavy, don't expect it to panic stop so fast. Did you do a proper brake pad bedding for optimal performance? If you don't get the correct transfer onto the disc, the pads are never going to bite hard.

There's some very good reading at stoptech.com. Look under the technical white pages. The section on the warped disc myth is excellent.

 

[swetrid]

Brake pads or rotor finish. Any type of ceramic or dustless pad definitely increases stopping distance.

 

[Vitos9th]

Thanks for your input guys. yea I hear ya that the explorer is heavy, but right now my 1st gen with rear drums is braking much stronger, so Im thinking there is still something going on.
I tried flushing the brake fluid, but it was my first time so hopefully I did it right, basically I repeatedly bled all the brakes (in the proper sequence) a lot while continually refilling the master cylinder with fresh fluid. Does that sound right? I made sure not to let the Master cylinder fluid level get low to allow air bubbles.
Thanks for the reference on the stoptech website, I'll definitely be reading that over to see what I can gain from it, and learn about proper brake pad bedding, I'm not too familiar with that term. I imagine you're referring to the mating surfaces of the rotors and pads, but yea i'll check that out for sure.
Another thing I'm wondering about, does anybody know much about the HCU, the hydraulic control unit? I don't know much about it, or how it works and I'm wondering if that is something I can check or test.
So, here are the things I'm going to do/check:
1. Read up at stoptech.com
2. Double check rotors, have them inspected/turned
3. Double check front hoses, possibly replace
4. Flush fluid again
I'll post my results, thanks guys and if there are any other ideas I'm definitely open to them, happy fourth of july!

 

[Vitos9th]

Ok, so after everything from my last post, after re-measuring the rotors, I decided to replace the front ones because although they weren't super super thin according to the minimum thickness, they were close enough. So, I bought new ones and regreased the wheel bearings and all that good stuff, and I made sure to clean the hell out of the rotors, etc. with brake cleaner to make sure there was no contaminants, etc.
I checked the lines again and they truly seem to be good so I didn't replace them. When I finally drove it, I did actually notice a big difference in how it stops. I really didn't think this was going to do it but yea, it feels way better now.
Oh, and I decided not to re-drain all the brake fluid since I did it before, it seems nice and clean.
Thanks for all your input guys, much appreciated.

 

[gmanpaint]

Do a simple brake line test by having someone else work the brake pedal while you watch the rubber lines. If you see them expand while pressure is applied, you know there soft and can use a replacement.

 

[Vitos9th]

that's a good idea, I did it with my pops, both of us taking turns to look and they look/act fine in that scenario. Thanks bro, luckily the brakes are working well now, but if my 1st gen has issues now I know to check the lines

 

[swetrid]

Like I said rotor finish makes a huge difference. Glad to see it fixed.