97 Pathy Brake pulsation. But its not the brakes!!!

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Rob458
Posts: 4
Joined: Wed Mar 30, 2016 3:20 pm

97 Pathy Brake pulsation. But its not the brakes!!!

Postby Rob458 » Wed Mar 30, 2016 3:29 pm

While braking, at any speed i have a nasty pulsation. The whole car judders like warped rotors/drums

I replaced the rotors and drums a few months ago. Made no difference
The rear lower arms were replaced, the uppers look ok. Im changing those bushings soon anyway just because. All suspension is good and tight

Could it be a slop in the rear diff? Axles?
Only happens when braking but all the brakes are brand new. Im stumped


Hawairish
Posts: 37
Joined: Sat Aug 22, 2015 9:02 pm

Postby Hawairish » Fri Apr 01, 2016 1:39 pm

Hope I can find an answer for you...my buddy's 02 R50 is also dealing with it.

On yours, does the steering wheel also shake violently? How does the brake pedal feel? His shakes violent at higher speeds and the pedal feels a little soft, maybe 75% of what mine feels (and it's pretty firm). Does it feel like it's just at the front of the vehicle, or the entire vehicle?

For his truck, we've:
1. Replaced wheel bearings (one bearing was on its way out after the wheel hub was loose for a while).
2. Eyeballed the pads and rotors; brakes only about 1yr/20k miles old, with plenty of material. I touched up some of the movement points with some brake grease.
3. Bled the brakes

Tomorrow is Round 2...we're:
1. Changing the steering rack bushings
2. Rebuilding his front calipers in case a piston or guide pin is hanging
3. Full brake bleed (including the master cylinder and ABS module)
4. Checking run-out on the rotors.

If it's not any of that, we're SAS'ing it. :twisted:

Rob458
Posts: 4
Joined: Wed Mar 30, 2016 3:20 pm

Postby Rob458 » Fri Apr 01, 2016 2:16 pm

The steering wheel does shake a little
The brake pedal when first applying will hold. then a second later will drop a tiny bit
Its hard to tell front/rear

When i changed the front rotors last year i never replaced the bearings. I might start there

Ive changed the rack bushings a few months ago too for a vibration

Hawairish
Posts: 37
Joined: Sat Aug 22, 2015 9:02 pm

Postby Hawairish » Tue Apr 05, 2016 10:23 pm

Well, we didn't solve his problem; still has the severe vibration during braking and soft pedal.

We did discover that the driver's rotor has a run-out of about .11mm, which jut exceeds the .10mm max run-out in the FSM. The passenger rotor was at .02mm. We tried reseating the driver's hub to see if perhaps that was the source, but it wasn't.

So, I suggested that he take it to the brake shop and let them reach their own conclusions about the cause (without telling them too much about our measurements on the rotor run-out, just so they don't say, "Oh yeah, that's it, we'll replace it for $X no problem!"). At this point, we've tried pretty much everything short of confirming a failing master cylinder, booster, or ABS module (no ABS codes though).


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