pulsating buzzing brake pedal/wobble at 40+

[xplorernewb]

i have a 93 explorer sport, recently ive been feeling a wobble when braking at higher speeds. now its getting to where it will do it at around 45+.
ive noticed that when im at a complete stop, i can push the pedal down and it will feel like its bottoming out at the master cylinder. like the push rod is being maxed out, but there is still a lot of pressure. seems like theres more travel at the bottom of the pedal than there was before.
also when driving on a dirt road, if i stop too abruptly, it will feel as if its bottoming out and make a buzzing sound as the tires lock up and skid.
if i hit a bump while pressing the brake pedal, it will also feel like its bottoming out and make a buzzing sound. front brakes were done about 30k ago (3 years ago) along with the bearings, and rears were done 2 years ago. tie rods, tracbar and steering gear are new within a year.

im thinking the rears may be out of adjustment so im going to check it out tomorrow. is there any way to check the pads and rotor without removing everything? its been a while since ive been near the brakes on this thing. anything else i should check please let me know, thanks.

 

[Rhett]

The buzzing sound is the ABS activating, so at least it still appears to be working.

I would say your rotors are warped, or getting warped, which accounts for the wobble you get when braking -- most noticeable at higher speeds. Low pedal could be a consequence of low brake fluid, I'd check the fluid level at the master cylinder reservoir.

Unless you have aftermarket wheels that let you peer in there, I do not know of any way to check the pads without removing the tires. If you remove the tire, there is a cutout in the caliper assembly that lets you look at the pads.

30,000 miles is plenty for a set of rotors on these trucks, so you're probably due to have them turned / machined at the very least.

 

[Rhett]

P.S. you should really be doing brake service more often than every 30k -- you should be lubing the caliper slide pins every 6,000-8,000 miles (or once a year, minimum). I lube mine twice a year. These trucks, if you have OEM brakes, really REALLY like to have the calipers lubed regularly, failure to do so results in warped rotors. Use a quality lube like 3M Silicone Paste, or CRC Silicone Metal lube. SilGlyde (available everywhere) is just "ok" but is not ideal.

Do not use moly or spray lithium, it will either not hold thru water, or will gum up.

 

[2stroke]

That's interesting about silicon paste. I'm a long time reader (not poster) on Bob is the oil guy forums. They are overly technical about greases and oils, but almost universally recommend Silglyde as the ideal brake grease. I've been using it for years without issue. The only problem I've seen is when people use regular nlgi 2 lithium, and it dries/burns out in short order. I'm certainly not against trying new things. If you know something proving another grease works better than Silglyde, I'd like to see it.

 

[Rhett]

I am around Bob is the oil guy too, and I know their love of Silglyde. I can only account for my experience with this truck. I was a long-time SilGlyde user (12+ years on this vehicle). Using SilGlyde, after 7-8 months, the pins would be 'dry'. Using the 3M, they're not. Proof will be, can I get more miles out of this set of rotors than last...I think I'm already past the mileage of my last set, and they were identical Wagners. A person can use whatever they want, it's probably about like asking "which oil is the best."

 

[natenkiki2004]

I was taught to use CRC synthetic brake caliper grease by someone very knowledgeable in parts and especially brakes. It works very well, is very tacky and thick without being difficult to work with and won't wash off.
https://www.amazon.com/CRC-Brake-Caliper-Synthetic-Grease/dp/B000M8IF1Q?th=1

Many people like silicone but to me, that stuff is too thin. I've seen dielectric grease melt and run quite easily and silicone spray often disappears too quickly. Silicone can be great but to me, is much more finicky than this CRC goo. It's got Molybdenum Disulfide, graphite and Teflon so it's very good at lubricating.

 

[xplorernewb]

thanks for all the information, ill definitely keep it in mind. i forgot to mention, most of the miles on the explorer are highway miles. its mostly just my traveling/hunting rig so it only sees highway and mountain side, not too many neighborhoods unless my pickup is broken.

anyhow so today i went out to take a look. had the front end up and one thing i noticed is that the passenger side front tire doesnt spin as loosely as the driver side. so im guessing thats where im supposed to lube the slide pins? is there a basic write up on that or? can i do that without taking the entire thing apart? the pads and rotors are good. pads still thick, rotors no grooves. passenger side rotor will be taken off for further inspection if fixing everything else doesnt help..

so anyway, i put the tires back on and noticed the boots on the lower balljoint (passenger side) were looking sad so i went to test and see if it was bad. no movement at 12 and 6. really stiff. but when i grabbed it at 9 and 3, there was a clunk at the tie rod. so i made it go clunk clunk clunk by wiggling it, and had my wife watch everything underneath. she pointed out that the slop stopped at the tie rod, but as i was wiggling it and watching as it bounced back and forth in the hole in the spindle causing it to clunk, we could see movement from the bad tie rod down the tracbar to the steering sector, making the steering wheel jerk upon impact. so new tie rod end is in order. funny though, i installed that tie rod about a year ago, and it was an oreillys zerkless tie rod end... so ill be looking for one wiith a zerk like the other side that didnt fail..... am i on the right track?

 

[natenkiki2004]

Cleaning the slide pins is 1 step further than where you just were with the tires off. Whack the pins out with a screwdriver & hammer, then the caliper comes off. With the caliper off, wire brush the surfaces that the pins sit in, they will be rusty. Clean the pins off with brake cleaner and assemble with whatever lube you feel like trying. It's that easy.

 

[xplorernewb]

so i replaced the tie rod today, nice and stiff. took it for a test drive and still have the vibration when braking but it seems to only happen going down a hill now. but no clunk. i went to lube the slide pins and noticed that the brake caliper isnt... well, how do i explain it..... it appears to be installed crooked? like, the line on the spindle and the caliper itself dont match up perfectly straight like the other side. i can push the piston back with a screw driver and spin the wheel easily but as soon as i pump the brakes its more difficult to spin the wheel again compared to the other side. its not super hard, but i do have to use more force by spinning the wheel one handed by the studs. i did grease the slide pins but i did not remove them completely because i didnt know if it would go back together properly because of its crookedness.. that and i have to work tomorrow and its being done in the driveway. i may have to take it into the shop if this requires the rotor to come off. crap

 

[natenkiki2004]

If I'm understanding you correctly and if I can depend on my memory... I think I had that happen to me when I put my passenger side together after doing u-joints and spindle bearings. From what I remember, it was due to the pad not being seated in the caliper properly, causing one side to be crooked. It would all go back together but it was crooked and weird looking. Look at the pads, they have tabs that fit into the caliper ears correctly.

 

[Rhett]

On my truck the calipers have never perfectly matched the spindle.

 

[xplorernewb]

well im pretty much dead set on it being the radius arm bushings on the passenger side. the plastic spacer or whatever is damn near completely gone. the only piece of it thats left is deformed and brown, and the rubber pieces are also deformed. luckily the rivets are drilled from the brackets already, which makes me wonder how long ago they were replaced since the drivers side is perfect. i went and bought the moog problem solver, HD bushings. comes with everything. i guess this will be my project when it isnt 12 degrees outside, along with new motor mounts.