2000 lesabre shudder when braking at 50 mph

[danshot]

I need heeeeeelp. My dad and myself have been trying to fix a shedder on my sisters 2000 lesabre limited with 170,000. Situation is: When going approx 50 mph or faster an lightly apply the brakes the car will shudder. A lot. Release the brakes and shudder disappears. Apply and they reappear. Below about 40 mph it's little or no shudder, something you could live with. But the higher speed shudder you can't live with. We have replaced the rotors on the front and had the back rotors checked, new pads on the front. Replaced the front Wheel bearing hub due to play. Suspention parts check good. The kicker is she, my sister has had the ABS, Traction off, and the brake warn light on for over a year and stiill drove the car like that. I'm begining to believe the ptroblem may be with the ABS. Does anyone know if the Abs system can cause a shudder or if the ABS light is on it renders it inop and therefore cannot be our problem that we need to look elsewear. Help us please, this is getting crazy. As soon as we think we found something we think is the cause and spend money, it doean't help one iota.

[gmtech1]

If the ABS light is on, the ABS system is inop. This sure sounds like a brake issue to me. You replaced the front rotors with no change at all? You are SURE the ball joints and tie rods are ok, control arm bushings are ok? What do you mean you had the rear rotors checked. They may be causing the shudder. Do you feel it in the whole car or just through the steering wheel?

[imidazol97]

Originally Posted by danshot

back rotors checked, new pads on the front. .

What happens when you apply the emergency brake while moving at a speed like 30 or 25? Do you get a shudder? Rears can be a problem because they are thin and not vented.

On the fronts, did you replace the calipers? I had a dragging caliper and it would heat up the rotor at higher speeds and cause a shudder that was there sometimes. I replaced the overheated rotors, pads, and the calipers all at one time on the front and that fixed it.

[danshot]

The shudder doesn't seem to be in the steering wheel, but when the car shakes of course the steering wheel shakes also. We did replace the tie rod ends, and checked the lower control arms, and ball joint. They check good. After the new rotors were replaced and had the same problem, we took them back off and to the store we got them from and they rechecked them on thier machine. We also removed the back rotors and and took them up there also. All rotors ck,d good. We did replace one front rotor. As far as applying the emergency brake at low speed. Did that and we get a small surging of the vehicle and also get that with appyng normal braking.

[GSGregg]

danshot; have you also checked the rear wheel bearings for play? Spun the wheels and checked for brake grab at certain points? Checked for dirt or imperfections in mating surfaces of rotor and hub?

Also, unevenly-tightened lugnuts can distort the rotor (obscure, but possible). A parking brake that doesn't hold properly can be left applied unnoticed and give the overheated rotors that imidazol97 mentioned.

[danshot]

I have not checked the rear wheel hub bearings. I thought my dad had, but i think i'll check them myself. The rotors on the back were taken off and checked for runout. they checked good

[danshot]

Does anyone know how hot the rotors would be after a 10 minute test drive. These were very hot after i took off the wheels after a test drive. I could grab them with my gloves on, but couldn't remain holding them. They were to hot.

[imidazol97]

Originally Posted by danshot

We also removed the back rotors and and took them up there also. All rotors ck,d good. We did replace one front rotor.

If I'm troubleshooting and I took the rotors off, I'd replace them or have them turned. I'm not sure that checking cold rotors is thorough enough here. How were the rotors checked?

If the rotors "checked" good, why did you replace one rotor?

Originally Posted by danshot

As far as applying the emergency brake at low speed. Did that and we get a small surging of the vehicle and also get that with appyng normal braking.

Then I'd start by replacing the rear rotors and carefully cleaning and lubing the slides for the calipers. On a 12-year old car, the calipers are likely to be problematic if they haven't been maintained or replaced with rebuild ones.

I'd apply the same careful inspection to the front calipers, and since the fronts are available cheap for rebuilt ones, I'd replace them.

[Tech II]

The thing is, you have to isolate, whether the fronts are pulsating, or the rears are pulsating....

Easy to do......Coming off the highway, just lightly touch the brake pedal.....LIGHTLY.....if that steering wheel starts shaking side to side, it's the fronts....if you feel in more in the seat of your pants, then it's the rear....

With that mileage, and the lack of maintenance, could even be both...

Since you are doing the work by bringing rotors in for inspection, are you following proper technique? You say you replace both front rotors...then brought them back, and they replaced one of the new rotors?

But you put both old rotors back on the rear?

You replaced the front pads, but reused the rear pads? Were the rear pads worn at a slight angle, for example, the front edge of the pad worn more than the rear edge?

When you put the rotors on, did you clean the mating inside surface of the rotors with a whizzer(all four)? Did you clean the mating surface of the hubs, especially around the lugs, with a whizzer? If you didn't, that's a potential problem.....did you lube all sliding pins? Did they move easily?

Did you clean the contact surfaces of the calipers where the pads ride?

Did you torque the lug nuts in a star pattern at 100 foot pounds?

ABS and traction off light is one thing, but having the RED brake light on is another....could be low on brake fluid, could have an e brake problem, could be the sensor in the reservoir, etc.

Has the vehicle been scanned for ABS and PCM codes?

[danshot]

After all those questions i think i'm going to start over with this whole brake job. I didn't start it, but I'm going to finish it. I'll update in a few days after i can spend some more time on the problem. abs codes were c1214, c1248

[danshot]

There was a slight change, per my sister, when the Mech up the road put on her new rotors for the shudder problem. She took it for a ride and said it was worse than before he changed them.

[imidazol97]

Originally Posted by danshot

After all those questions i think i'm going to start over with this whole brake job. I didn't start it, but I'm going to finish it. I'll update in a few days after i can spend some more time on the problem. abs codes were c1214, c1248

You've got several things to check. This has to be diagnosed by you onsite.

Some of the information seems contradictory: one new rotor on front? or your sister had two new rotors on front where you said the character of the shudder changed after the new rotors.

My own guess, sort of feeling the elephant by a blind man, is that your caliper on front is dragging. That heats the rotor creating a hotter heated area in the high spot. This really drags when the hot spot comes to the pads each time. The fresh rotors with rough surfaces reacted even more to that dragging and hot spot problem.

I see the solution as fixing the problem with new rotors, rebuilt calipers, and new pads on the front.

[danshot]

Upon reading my own messages, i do see that i"m all over the place on this. I apoligize for jumping all over. I think i'll take your advice and do a total new front brake job. Even though there are new pads on front, new rotors on front, New left wheel hub on front, new tie rod ends on front. The back remains as it was, nothing new, just a visual check and rotors checked off car in the shop. When it's fixed ill update. My dad is leaning toward the ABS. Hope he doesn't spend too much on that.

[imidazol97]

Originally Posted by danshot

I think i'll take your advice and do a total new front brake job.

You can save your fairly new pads for the next pad change and the rotor that was replaced as a spare...

Originally Posted by danshot

My dad is leaning toward the ABS. Hope he doesn't spend too much on that.

You can always unplug the ABS or take the fuse out and drive to verify it still acts up without the ABS being active.

Good luck.

PS> I put off doing my 98's front brakes which were doing something similar until I was ready to do all three, pads, calipers, rotors. OEM quality pads, no ceramics, no longlife metallics, and the car felt like it was fresh off the showroom for stopping and characteristics of the brakes.

It had a grabbing at higher speeds after it had warmed up the high spot on the rotor and did not do it at lower speeds in town because the high spot never got reheated. I lubbed the slides on the caliper, freed the piston up, but nothing seemed to fix it. At 60K or so, just changed everything. I did put on quality Raybestos top line (not drilled and slotted) rotors.

[danshot]

Rotors, Rotors, Rotors, Rotors, Rotors.... The fix was the rotors. The new rotors were bad, even though O'reillys checked them as good. So they are turned all 4 rotors, no charge. The fronts really made a change, then the rear smoothed it out the rest of the way. I learned a lot from this thread, and will heed the advice of the members about brake work. I appreciate everyones input and expertise on this subject.