kukx30de

iTrader: (4)

I need some help in diagnosing this.

Recently, I have noticed as I brake at slow speeds i.e. under 25mph, the brakes are pulsing. Basically, if I have not depressed the brake pedal all the way, it feels like the brakes are working but they grab, let go, grab let go.

I thought I had air in the lines, so I did a bleed but no difference.

I dont think its the rotors because if I brake at higher speeds, i.e. over 65 there is no shimmy or vibration.

Suspensionwise everything is tight and recent if not brand new.

I'm leaning towards a caliper that is not releasing or engaging properly. The funny part is sometimes, it feels like its happening in the front and sometimes in the rear.

I have also found that if I do a couple of hard stops i.e 60->10 a couple of times like I am bedding the brakes, the issue goes away for a few days and then comes back.

Any thoughts/feedback? I'm thinking off popping the calipers and just doing a preventitive seal service since they are OEM and have about 197K on them now

rroderiques77

iTrader: (45)

So the brakes apply when you do not apply them? That's odd. How do you know it's in the brakes and not some kind of surging or hesitation while driving.
If you are going to reseal calipers, good luck with the rears. They are ratcheting calipers and I do not recommend opening them up.
Brake rotor vibrations may only occur at slower speeds, depending on what kind of run out you have on the rotors.
If you are capable, bust the tires off and measure run out in all four corners. Any rust in the calipers? With that many miles, it probably wouldn't be a bad idea to replace them if the brake system is OEM.

vinco

iTrader: (3)

The problem is probably your pads. Replace them with good ones, i.e., ceramic pads or EBC or the like.

While you're at it, it's a good idea to clean and lube the slider bolts on the calipers, as well as the stainless steel clips upon which the pads slide.

I would personally NOT recommend changing the piston seals in the calipers, as I have found this operation to yield spotty results, in terms of success. I've rebuilt many calipers before, but for whatever reason, the rears on my Maxima just would not seal after I rebuilt them. I ended up just buying a rebuilt caliper, since a new piston costs over half as much as just buying a whole rebuilt unit.

kukx30de

iTrader: (4)

Thanks guys.
@Rochester - the brakes apply when I step on the pedal but pulse when the pedal is depressed like 40%.

I'll def check on the pads. The ones on there are ceramic right now but the rears are cheap advance auto parts pads. I'll check the slide pins and relube them with caliper grease.

Fun for the weekend.

njmaxseltd

iTrader: (19)

Pulsations, vibrations, ect come from the moving/rotating parts (rotor) not the pads.

nelledge

iTrader: (6)

Maybe a silly question, but do you have ABS? Some cars do that when the ABS sensor needs to be replaced. You wouldn't feel it as much at higher speeds.

Rochester

iTrader: (3)

I think you mean rroderiques77, not me. Apparently I wrote something once that resonated with Roy, and he put it in his sig. Hence the confusion.

Carry on. Good luck.

BTW, have you tried bedding in your pads to your rotors? Couldn't hurt to try, and gives you a justifiable reason to beat the crap out of your car. That's always fun.

homeyclaus

iTrader: (1)

Any pulsing in the brakes is a rotor issue 9 times out of 10.

Based on what you say the symptoms are is that you have a hard spot somewhere on a rotor or something. Re-surface the rotors (starting with the front) and it should go away and stay away.

2slow

iTrader: (6)

Do your rotors look like this?



A good read: http://www.stoptech.com/tech_info/wp...akedisk.shtml#

Lemonhawk

Warped rotors. At higher speeds its doing the same thing, its just so fast that you can't feel it and the piston may not respond to the pulsing. As the disk warps more the pulsing becomes noticeable at higher speeds. It will probably cause the pads to ware sooner, then you can have the rotors replaced or resurfaced if there's metal left. If you do your work, its probable better and easier to replace them. you can do one wheel at a time then.

ghostrider17

iTrader: (6)

2slow

iTrader: (6)

You need to read this ˅˅˅˅˅˅˅˅.

An excerpt:

P. Samson

By any chance do you hear the ABS system operating (or is the brake pedal pulsating) when you have the brake "pulsing"? Has the ABS light ever illuminated after one or more of these "events"?

K-Ryder

iTrader: (1)

You have warped rotors. Replace them and you'll be ok, Yeah you can have them resurfaced but chances are they can be off when being resurfaced. And it would be a waste of time. So just by a new set of rotors and call it a night.

ghostrider17

iTrader: (6)

Rochester

iTrader: (3)

LOL, Nate! That really was funny.

Even funnier because K-Ryder doesn't know why it's humorous.

2slow

iTrader: (6)

Once again:

Another excerpt (some emphasis added):

ghostrider17

iTrader: (6)

I've been waiting to use the "facepalm" for a while now....!

I actually re-read the Stop-tech article on "Warped Rotors" again this morning....such a GOOD READ, and highly informative!

I recommend it for all of those (hint-hint) who are still referring to this issue in the past-tense, incorrect terminology.

Edit: EVEN funnier that 2slow reposted that BEFORE I posted my comments!!! Bwah!

Rochester

iTrader: (3)

2slow, no one has time to read something educational.

Just tell us how the rotors get warped.

2slow

iTrader: (6)

He must have been driving flatout.

kukx30de

iTrader: (4)

Just a quick update.... So I had done new rear rotors and pads last yr. This morning put on new front rotors and pads. Did a bedding in session. Darn issue is still there! So now hv to do the rears again ... Just my luck the fronts didn't look bad so let's see if I can get any store credit.