weird brake issue

[nj300se]

I have a 92 Nissan Sentra SE-R with an odd brake issue that maybe someone can help me with.

For some time now, when I brake from speeds of say, 30MPH or less (think slowing to a stop sign or red light) the car "pulses" almost like when you have warped rotors. There is no pulsing in the pedal. Last year, I replaced the front rotors and put on new pads and the problem went away. Within 4 months the problem returned.

The car stops fine, and at highway speeds it is not an issue at all, meaning that if I brake there are no vibrations or pulsing at all.

Its driving me nuts. No mechanics seem to have a good answer. Any ideas?

 

[Dark Jedi]

have you had your rear drums adusted? if not your rear drums might not be enguaging fully. causeing your front rotors to do almost all the breaking and cause to to heat up really good. causing them to warp.

 

[DriveHard]

where the wheels put back on with a torque wrench? If you over torqued the lug nuts, its easy to warp rotors again within a couple hundred miles. I learned that the hard way myself.

Also...did you break in the new pads and rotors with a couple good hard stops? If not, you may just have a build up of pad material on the rotors.

I would pull them back off and have them turned. Its an easy way to make sure they are true without spending a ton of $$$.

 

[Dark Jedi]

just assumed they was drums in the back.

 

[AcuraTech]

quote:

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Originally posted by DriveHard:

Also...did you break in the new pads and rotors with a couple good hard stops?

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We were taught in tech school that you should take it easy for the first few hundred miles.

 

[nj300se]

There are disks @ the rear as well (not drums)but I had not giving that much consideration to the rear because I was focusing on the front. Hmmm.

I'll check how the rear disks are wearing. Thanks for the idea!

 

[JAYCEE]

Avoid puddles of water. Water will warp hot rotors.

 

[punisher]

A good way to tell if front or back rotors are causing pulsation, get to speed and gently apply the parking brake. This only works in vehicles that use the rear caliper as a parking brake. For cars that use the miniature drum brakes on the inside of the rear hub/disk as parking brakes this test doesn't work.

 

[nj300se]

Thanks everybody for the tips! I'll try thr parking brake test to see how that turnsout. It does seem that the rear disks are not breaking evenly as there are areas on the rotors where it is nicely worn and shiny, and others where it looks like no contact at all is being made. Maybe, as Dark Jedi suggested, the front disks are over-compensating for the rears.

The rear rotors (still original) are cheap enough to replace (Dad works @ a NAPA) so what I am thinking of doing is replacing the rear rotors and pads and re-turning the fronts. The fronts are less than a year old. That should also take care of any pad material thay may be causing the pulsing as well.

Thanks so much everyone for your ideas and suggestions!

 

[LubeOiler]

I had a FORD once that they changed out all the rotors and pads at 8000 miles due to pulse braking. I found out they used some kind of new type pad that caused it. I put the top grade pad at NAPA and never had trouble after, but they had to turn the new rotors again but it lasted till I traded it for a Acura.

 

[Not the Autorx Frank]

I'm willing to bet the fronts ar warped again. did you check the runout again in the front? some rotor pad combos go south within 4 months easy. oem is always my choice w/ brakes.

 

[nj300se]

"did you check the runout again in the front?" pardon my ignorance, but what does "runout" mean? I'm pretty sure I have not checked it!

I used the Wagner thermo-quiet pads with made in USA, but not OEM rotors. (I forgot the brand)

 

[Tosh]

On a car which has spent 15 winters on salty roads, I would expect the brake caliper pistons to be frozen up.

 

[The_Jeff]

quote:

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Originally posted by nj300se:
there are areas on the rotors where it is nicely worn and shiny, and others where it looks like no contact at all is being made.

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You aren't talking about the couple millimeters on the inner/outer circumference? That can be rusty and okay.

But if you have one part of the arc that's rusty and the other shiny, you have a seriously crazy problem!

I would also check the hub flange for rust that could keep a rotor from sitting correctly and even wheel bearings for looseness.

 

[ikeepmychevytoo]

indeed... If there is any evidence of rust in the center of wheel the regular practice should be to clean all the loose rust with a wire brush before re-mounting the wheel.

However, vibration when braking only at low speeds and no pulsation on the pedal makes me think that this may be a tire problem. Radials tend to develop uneven resistance as the carcass is messed up with (us)age. If nothing obvious can be found I'd swap rear radials with fronts too see what happens.

 

[moribundman]

What about a bad wheel bearing? That might cause the hub/rotor assembly to wobble.

 

[michaelc80]

quote:

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Originally posted by nj300se:
"did you check the runout again in the front?" pardon my ignorance, but what does "runout" mean? I'm pretty sure I have not checked it!

I used the Wagner thermo-quiet pads with made in USA, but not OEM rotors. (I forgot the brand)

---

Lateral runout is what he's talking about. More information at this site.

 

[ChrisW]

bleed the calipers. also your m/c may be leaking and bypassing causing uneven pressures to the caliper pistons.

i had the slight pulsation (in the steering wheel not felt through pedal) in my bros car, changed pads to hawk hps and rotors and it went away, but interesting to note that the brake pedal was really touchy; if you depressed the pedal the slightest it was like full-on braking. I believe there was air in the lines and sure enough when i cracked open each bleeder screw two or three bubbles came out.