Humming/Pulsation: Bearings?

[tajvelocity]

More woes for the Mazda (99, 2.5 2wd, coil sprung, 126k). I've noticed a hum above 40, especially turning right above 40, coming from the front of my truck for a couple months. I've also been having brake pulsation for a few months or more as well. Actually I can't feel pulsing in the pedal, but the whole truck kind of lunges forward and back when I hit the brakes. I lifted the front and rocked both wheels back and forth. I can feel a tiny bit of play on the driver’s front but not the other side. I guess that means my wheel bearing is shot on that side? I replaced the rotors, pads and bearings less than 30k ago I think. I’m no mechanic so it’s possible I screwed something up, but what? Could the pulsing be caused by a bad bearing? Here’s what my rotor looks like:

Is that normal looking wear? The pads seem to have plenty of material left. Moving the rotor back and forth like I do when the wheel is on, I feel no play. Also when I spin the wheel there is a dragging, metal on metal sound on both sides. I don't know if that's normal. Here's a video, I hope the link works:

http://www.flickr.com/photos/tajai/8635569687/

Also, I just had the tires rotated and they neglected to inform me that there's a nail in a tire. I doubt that could be causing any wobble but still. Also also, I replaced the upper control arms around the same time as the brakes and the ball joint on the passenger side has a rip in the boot already. Awesome!

Am I experiencing premature wear on stuff or what?! What am I looking at replacing again? I'm leaning toward driver's side bearings for the time being and hoping that cures the hum and pulsing. I'll worry about the UCA later when I score some factory alloy wheels and take the 2.5" lift spindles off. I'm considering just taking it to a shop this time, but the thought of a ~$500 bill terrifies me.

Thanks for looking.

 

[alwaysFlOoReD]

I'm not a licensed mechanic or super knowledgeable about brakes but....
I think it's a warped rotor. Have you got the brakes real hot, like coming down a mountain with brakes applied for long periods of time? You may be under warranty still, exchange that rotor for another and if the parts place will go for it, the bearings too.
Good luck,

Richard

 

[tajvelocity]

Thanks FlOoReD. I don't think I've had many braking scenarios come up like the one you've described but there have definitely been panic stops when the flow of traffic in the left lane suddenly goes from 70 to 0 for no apparent reason. I got the last round of parts from Advanced Auto. I wonder how their warranty works? If I get new rotors and bearings, I should probably go ahead and do the pads too? I guess BOTH rotors could be warped as the metal on metal sound happens on both sides when I spin the wheel. I can't notice that sound while driving. I've also never bled the brakes, partially because I'm scared of screwing it up and the fact that I generally don't have access to a helper. Also I hear it's very time consuming, but I've been doing a TON of maintenance on this truck in the past year or two so what's a few more hours I guess. At least it's getting warm out.

 

[aspevacek]

Yes when every you swap rotors always put new pads on and ensure you bed the pads in properly.

Check out Rock auto for rotors they generally have really good pricing on stuff. I use Centric on my impala I got from there. I had ordered Raybestos which used to be one of th ebest brands you could get for brakes but it appears they to have moved to China for production of rotors and they are about trash. I ordered the lower priced Centrics for my impala and have had no problems since.

When every you change front brake pads you need to colapse the piston back into the caliper. You should always crack the bleeder valve open as you compress the piston to keep shit from getting pushed back thru your brake system. This is especially important if you have ABS on a vehicle. I have rebuilt many ABS control unit and pump assemblies on BMWs because peopel trying to do thier own brakes and force shit filled fluid back thru the system and clog up control valves.

 

[tajvelocity]

Well hell. I've never cracked the bleed valve when compressing the piston
(with a c-clamp and a block of wood). I don't have ABS but the Haynes manual didn't call for it. Obviously they're not the best resource in the world though. Does fluid come out when you crack it open? Is it time to bleed the brakes as well? What about the grinding sound in the video. Is that normal? With the wheels on I can spin it pretty freely but is makes that sound (crank up your speakers/headphones!). I guess it could be that the Advanced rotors are lousy (Wearever I think). It could also be that I braked too hard one too many times. I wonder if my caliper needs to be rebuilt if it's dragging.

The bearing issue: I'm pretty sure I used Timkens which are supposed to be pretty good. I do have heavy steel wheels on there with 31's but they should still last longer than ~30K I would think.

There are a lot of things that could be going on here I guess. The only thing I know almost for certain is that the driver's side front wheel has some play and that I probably need bearings on that side. I just don't know why. There are a lot more components to the braking system obviously and a lot of things that could be messed up.

Frustrated.

 

[alwaysFlOoReD]

When I was listening to the vid I was hearing the scraping sound for half of one rotation. That's why I was thinking a warped rotor. Heat is one possible reason for a warped rotor. It could also be crap steel that has worn down more in one spot or one spot that's harder than the rest and hasn't worn down as quick. Actually this fits into the pulsation better than having a warped rotor, as the rotor is thinner on one half compared to the other. In any case a new rotor is what I would do. New pads makes sense too.
As I understand calipers, there is some residual pressure in the line, about 2 lbs, that keeps the piston pushed out toward the rotor. At the same time, the seal of the piston is slightly rolled and when the brake pedal is let off pushes in the opposite direction but not enough to overcome the residual pressure. So... there is a very slight drag of pads against rotors. This is normal.
If one rotors bearings can't be adjusted to where there is no slop, there is a problem. There is wear somewhere and one possibility is the bearing races that are pressed into the rotor. Another possibility is the race to spindle. I've seen one race that was loose, causing the problem you seem to be experiencing. Changing rotors and bearings could solve the problem. But it could be spindle wear too. Take it apart and clean really well, and then a very close inspection.
I would also really try for warranty replacement. If you've dealt with the parts place more than once, they will probably work with you, even if past warranty period.
I hadn't heard about screwing up abs but that does make sense, I will have to start cracking the bleeder from now on.
Anyways, good luck,

Richard

 

[tajvelocity]

Yeah I think I'll just replace the rotors/pad/bearings. I think I might as well lose the lift spindles while I'm at it and put the stock ones back on (with 2" lowering springs). That was the plan all along but I hadn't anticipated doing brake work at the same time. I'll see if Advanced will warranty my stuff. I'm sure Rock Auto is cheaper, but I need to start on this mid next week and don't want to wait for shipping. Side story: I'm house/dog sitting for my woman's sister and brother and law. They have a nice flat driveway and garage whereas my usual work space is a banked gravelish driveway at my grandmother's house way out in the sticks (I live sort of in the city with street parking so not much maintenance can get done there). Still looking for cheapish stock rims with tires on Craigslist. Side question: will 14" deerhooves fit over my hubs and clear my calipers do ya think? Again, 2wd, no ABS, and I think I have the smaller rotors. I've also found some gen1 or 2 steelies on CL and I'm wondering if those would fit.

I'm driving the spare car now (soon to be sold I hope). I have to haul some stuff to the dump tomorrow. I might try to snug up and tighten the bearings on the bad side before I do.

 

[zekew64]

What I would do is take off the caliper and pads and rotate the rotors while looking at the side of them (where the fins are). What you need to look for is side-to-side movement; if you have even the slightest, you have warped rotors.

Also, if you have looseness on the driver's side, it could be bushings or ball joints, besides bearings. However, if it is the bearings, it sounds like they simply need to be repacked and adjusted properly. The way to adjust the bearings is to tighten the nut up all the way, then loosen it a half-turn or so. If you do this, make sure that the bearings have plenty of high-temp grease.

 

[Jay'94]

You could be warping your rotor from tightening your lug nuts wrong or too much.