sticking breaks, caliper rebuild required?

[katalenic]

my front breaks seem to be sticking, getting pulsing sensation when come to slow/moderate stop. Pads, Rotors check out fine for wear. Mechanic suggested I lube the calipers. Any tips on how to simply lube the calipers, do I need to take them all apart, and would it be wiser to just rebuild the calipers or is this overkill?
I'm planning to flush the break fluid at the same time.
Thanks, 328i 1998 with 152k

[Jeron]

Take the front brakes out and lube the guide pins. While it is apart, closely inspect the dust boot around the piston, if it is dislodged then rebuild the caliper.

[Jeron]

The first thing I would suspect for your issue is brake pad deposits on the rotor causing the pulsing sensation.

[katalenic]

I need to get in there to replace the wear sensor anyway, I'll clean up the rotor really well with break cleaner and see if that helps. I'll lube the guide pins when I flush the brake fluid too. Thanks for the suggestions, I"ll let you know how it goes.

[Jeron]

Brake cleaner on the rotor wont help. You would have to use Garnet sandpaper to get the deposits off.

[katalenic]

you were right, I tried to use the brake cleaner while had the wheel off to snap in the new sensor, but made no difference, but can't find anyone who knows what garnite sandpaper is - where would I find this.
Someone suggested the rotors might have a high spot?
Pulsing only occurs or noticeable, at low speeds
Not yet greased up the calipers

[Jeron]

Garnet sandpaper is very common and is available at any store.

Read this
http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

[Jeron]

I think you will have better luck redoing a brake bed-in procedure. I think it is described in that article i linked above.

[katalenic]

Jeron, would you recommend replacing the pads and going through the re-bedding process described, or can I stick with the existing pads?
Either way, would you still do the garnet sandpaper cleaning? Hate to sound dumb here, but do you dry sand in a circular fashion, cross grain, or with the grain of the disc? This is driving my wife, and therefore me, crazy.

[Jeron]

I have never had much luck with the sanding, personally. Yes, dry sand. The best thing would be a power sander of some soft because it will take a lot of effort by hand. I would use 1/3 sheet vibration sander which is about $20.

A brake bed procedure with the existing setup costs nothing but 30 minutes of your time. Usually this only fixes it for a few weeks, then the original cause makes it happen again.

News pads and rotors is the best bet but make sure you get the right pads. BMW pads will be the best for not making noise but they create lots of dust. The second quietest pads I've had are Oreilly Lifetime made but Textar. Hawk HPS have been very good but as they age they have started to make a little noise, no vibration though. I hate BMW pads, BTW. WAY TOO much dust.

How old are your rotors?

You should consider rebuilding the calipers. They are a likely cause.

[katalenic]

Thanks, I'll replace the pads and rebuld the calipers - looked like the kits were pretty inexpensive.

Rotors, not sure how old they are, just bought car used with no history, dealer said they looked good, but they didn't find this brake issue either - so whatever that's worth. I can mic them and see how much is left, but independent mechanic also thought they looked OK, but again they couldn't diagnose this brake issue either. - why is it so elusive to these guys who do this for a living?

The rotors also looked relative inexpensive, may replace them if following plan does not work

I plan on the following list
-sand face of rotors with garnet sandpaper and random oribital sander
-flush brake fluid completely
-rebuild calipers, grease everything up good
-replace front pads
-perform pad bed-in process
-hope for the best!

Thanks for your help, any link with good/valid info on how to rebuild the caliper appreciated, I've read some posts that the instructions online are incorrect

[Chilly]

Are they pulsing, sticking, or both? My 97 328 rear caliper was sticking, wheel got very hot. Diagnosed that the boot had come partially loose and suspected corrosion. Tore it down and was told I would not be able to reinstall the boot and to rebuild. I cleaned up the corrosion with emory paper, rinsed with brake fluid, and installed the old boot (wasn't torn) and it has been fine since.

[katalenic]

They feel more like pulsing, but only noticable at lower speeds? Don't notice at all at higher speeds or hard stops. Someone suggested that it may be the tie-rods and not the caliperor rotors at all. I know the tie-rods need replaced (per dealer inspection), but wouldn't I notice the "pulsing" at all speeds?

I planned on the new rotors and pads replacement later this month, but now doubting myself that maybe the tierods are the real culprit?
Anyway to diagnose or eliminate one from the other?

[Chilly]

I guess my advice on diagnosing the true cause is to fix what you know is wrong and see how it goes. Or get a dial indicator with a magnetic base and check your rotors for runout.

[katalenic]

I replaced the rotors and new pads for only $85 - all is well!