Vinnie T

Need help and/or ideas, as I'm trying to avoid taking to the Totota dealer if I can help it. Not a pleasant bunch to deal with, and they have a hard time listening to their customers.
This is on a '02 Tacoma Prerunner D-Cab. The front brake pads were worn, so I decided to replace them along with the front rotors since I was feeling some pulsation in the braking and assumed (bad thing to do) the rotors might have some warpage. The pulsing was that on/off feeling as you stop, but no shaking in the steering wheel. I went with Brembo rotors and Akebono ceramic pads, and everything seemed OK for the first week, with the exception of still feeling some pulsation when stopping. Had to then take the truck into the dealer to replace the LF shock under warranty since it was showing signs of leaking. About 3 days after that, the pulsations started getting more noticable when braking, and turned into a strong shudder throughout the whole truck (up and down vibration) under moderate braking from high speeds. But still nothing much in the steering wheel. This becomes more pronounced as the brakes heat up. I checked the LF shock for being loose. While it was, tightening the upper mount did not have any affect on the braking issue. I'm not seeing any noticable warpage of the front rotors, at least nothing that would cause this. Everything is tight in the braking sytem and suspension, and I even went and put OEM Toyota pads back in to see if the Akebono pads were an issue. No change. So for the hell of it, I even replaced the rear drums to see if the pulsating issue was coming from the back since it was there before and after the front rotors were repalced. Again, no change. There is no vibration during non-braking driving which would seem to discount anything else (hub flange, etc.) being bent or out of round. The only other maintenance item the truck needs is an alignment that I normally do after getting tires, which I've done in the middle of all of this.

So, new front rotors, pads (and shims), and rear drums, but now a shudder/vibration much worse than when I started. Any ideas?

LittleRedToyota

wild guess, but maybe your ABS is malfunctioning (maybe sensing that your wheels are locked when they really aren't and then "pumping" your brakes for you or something)?

(i don't have ABS on my truck, but on previous cars I did and when it is doing it's thing, it can feel a bit like warped rotors.)

prolly not it, but maybe something to check out.

Vinnie T

This one isn't equipped with ABS either. But that's a good analogy as far as what it's kinda feeling like. Gets depressing trying to figure this out when logic doesn't work anymore Thanks!

4Hummer

Could be the Master

instigator

Vinnie, i'm getting the same thing on my truck, the exact symptom you described. i also changed rotors, pads, shoes to no avail. i will be looking at the ball joints to see if they are worn (might help, might not) i also think its the abs sensing something ironious in the system, but i'm not getting any abs lights to notify of such action. hopefully we can find the culprit in this thread.

Flamedx4

Instigator - you should be able to disable the ABS (unplugging the fuse is the simplest way in most vehicles) and test it that way. ABS is passive - if disabled it will have no effect on your braking.

VinnieT - Time to start checking the things you haven't done - brake lines kinked, bulged, melted, pinched, master cyl, proportioning valve, etc. Look at the calipers closely - slide pins rusty? It would be handy to find another one like it and check yours against it to see that everything was assembled in the right order. It's a bit odd that you felt the need to buy new rotors and drums for an '02, barring damage they are normally good for a long long long time. (Mine are still factory at 215K for example) WEre the new rotors the correct ones? Did the bearings go back in properly? Axle nut torqued properly? etc...

Just a nuther thot - I have more than once seen brake shudder of the type usually caused by warped rotors being caused by grossly overtightening the front lug nuts.
My point is - overlook nothing!

Vinnie T

Thanks for all of the thoughts and ideas.

instigator: No ABS on this model. Unfortuantely, it didn't come standard til '03 if I remember correctly. But it is a good analogy as to the way it acts.

Flamedx4: I know what you are saying, as I'm also pretty thorough with this stuff even though I didn't mention some of the smaller things I've done. That's why I'm so frustrated by this. I'm quickly running out of things to look for. Everything points to something being loose or out of round, and I can't find anything that meets that description.
The brake lines are straight, open and clear. I buffed the light corrosion off the slide pins, and made sure the calipers were in good working order. The Brembo rotors are identical to the OEM units that came off. Everything went back together just as it came off. When I reinspected the pads after the shudder worsened, I even bonded the shims to the pads using that Permatex Disc Brake Quiet goo so that there would be no potential vibration sources. Didn't make a difference though. Bearings aren't a direct issue since the rotors do not house the bearings. The rotors are the "hat" type that fit onto the wheel hub. I too thought it odd that I would be getting a warped rotor pulsation after about 15K (it now has 33K), but rotors can warp quickly if exposed to quick hot/cold cycles. Or over and/or inconsistent torquing of the lug nuts as you mentioned, but I used a torque wrench for all final tightening. But as you pointed out with your rotors, these OEM's didn't look badly scuffed or warped when I took them off. That's when I started looking at the rear drums as a possible cause when the pulsation was still there after the new rotors were on. It was a long shot since drums usually don't have out of round issues very often. However, I'll look closer at the brake shoes and auto adjusters to see if anything looks odd there.

Mickdady

As an experiment use the parking brake to stop the vehicle. (don't let it ratchet). Do this in a parking lot at slow speeds. See if you feel the shudder in the parking brake mechanism....this would isolate it to the rear of the vehicle.

Vinnie T

Mick - I tried the parking brake at lower speeds (too much traffic at the time) and really couldn't duplicate it. I'm going to find a nice open stretch on the way home today and give the it antoher try at higher speeds. Thanks!

Vinnie T

Good call Mick

Was able to duplicate the shudder using the parking brake from about 55 mph with the truck in nuetral. The hotter they got, the worse it got. Did 3 semi-stops like this. Defiinitely something going on with the rear brakes. Waiting for them to cool right now, and will pull the drums off this evening and see if I can figure out what it is. Thanks all, and will let you know what is found in case this comes up with you.

instigator

well i think it might be gone now, i re-replaced my front rotors and the pulsating is gone. even when they got hot. i've got only 1 day on them so we'll se if that did the trick.

belgichocolate

After replacing a drum on my van, I was braking and the shudder was incredible. Did you try seating your rear brakes by braking with just the emergency brake...carefully of course. This helped me out.