Pulsating Brake Pedal

[Milliterate]

I've searched and can't find any threads with the exact same problem as mine. My s13 just recently started pulsating and making a light thumping noise under medium to heavy braking. I can feel the pulse in the pedal, so I thought it was a warped rotor or uneven pad wear. I've replaced the front rotors and brake pads and bled the brakes, but the problem still exists. I don't believe it is the rear brakes, as the caliper sliders are seized on both and they honestly don't hardly work at all, not to mention, the caliper bracket bolts are sheared off, so I'd have to get an entirely new spindle to replace the rotors. It sounds like the thumping is coming from the front as well.

This seemed to start after I put new struts on the front. I've double checked all the nuts and bolts and everything is tight up there. I had the front on jack-stands for about a week with the struts pulled out and the control arms hanging only from the sway bar and tie rod, could that have damaged the sway bar bushings? Would that cause a stuttering front end when braking? I can't figure out what this might be, or why I can feel it in the pedal. Help!

[satek]

Check your tension rod bushings...they are probably cracked and leaky.

[revcyanide]

this, or alignment.


i tottally thought this was someone who has ABS and didnt know it when i red the title

[RedSiBaron]

How are your tie rod ends?

[Milliterate]

Tie rod ends are new(er), no blown ball-joints. tension rods are aftermarket with pillowball instead of bushings. Those components are fine.

[Milliterate]

And yes, no ABS.

[hOngsterr]

yout tension rods might be upgraded, but did you make sure the locking mechanism is tight?

[Milliterate]

The jam-nut? Tension rods appear tight. Someone said maybe it's the wheel bearings?

[RedSiBaron]

Wheel bearings should be making noise under load, so I doubt its that. Plus I've never had a bad wheel bearing shudder under braking...

Does your diff clunk or roar on engine brakin? In my s13 I have a wicked ill adjusted diff in it now (rebuilding/tricking out another) that does the job, but it roars under decel, clunks under sudden load and shudders under certain braking situations.

[Milliterate]

Diff doesn't make any noise under engine braking, and I engine brake quite a bit. I'm gonna check these struts out again, seeing as that was the last thing I did before this problem occurred.

[RedSiBaron]

Have you checked your engine mounts/trans mount? I mean who knows but my car did shudder under under decel and some braking wheen I had the old stock blown mounts (like the drivers side mount was in two pieces)...

[KiLLeR2001]

I don't believe it is the rear brakes, as the caliper sliders are seized on both and they honestly don't hardly work at all, not to mention, the caliper bracket bolts are sheared off

:picardfp:

Fix this first.

[Milliterate]

I know...that's on the list. But for now, I need to fix the problem at hand before I can drive the thing comfortably. The car was stopping fine under the power of the front brakes, with little help from the rear.
I know the rear brakes aren't causing a problem right now, so I need to focus on the problem that exists in the font.

[KiLLeR2001]

No. You need to stop driving your car until your brakes are fully functional. Driving around with bad brakes is probably one of the stupidest things you can do, right next to driving with bald tires in the rain.

[Milliterate]

I'm not driving the car right now. I can understand that it's unsafe to drive in it's current condition. Good thing I just bought an 89 D21 pickup last month..

[csmith21]

I know...that's on the list. But for now, I need to fix the problem at hand before I can drive the thing comfortably. The car was stopping fine under the power of the front brakes, with little help from the rear.
I know the rear brakes aren't causing a problem right now, so I need to focus on the problem that exists in the font.

Fixing the rear brakes would eliminate another factor in your problem, even if you don't think it is. Besides the fact of how unsafe it is, it's something that needs to be taken care of anyway, so why not spend the extra effort in fixing something that could potentially solve your other issue.

[Milliterate]

I'm beginning to think it's excessive lateral runout after doing some more research on pulsating brakes. It could be that my hub is warped or has thickness variation. This would make sense if the problem was more defined after putting on new rotors. I'm going to get a dial indicator and check the rotors, wheels and hubs for runout before proceeding with anything.

[Milliterate]

Looks like a brake booster vacuum leak may be the culprit of all of this. Although I did check my runout, and my driver's side rotor is out of spec by .003.4", enough to cause pedal pulsation apparently. This will have to be fixed with shims.

[Howie Felter Snatch]

I'm going to have to just FYRB on this too..


Dude

Seriously

Fix

Your

Rear

Brakes


I cannot beleive you drove with seized rear calipers and sheered bracket bolts.. :eek:

I mean I know 240 owners are ghetto, but damn not this ghetto. j/k <3

[rcdad123]

if the brake pedal pulsates but the steering wheel does not vibrate when you step on the brakes, it`s the rear rotors. if the steering wheel vibrates when you step on the brakes, it can be the front rotors are warped or a loose suspension/steering parts condition. if you think the problem is in the front, get a buddy to drive the car while you stand on the sidewalk and tell him to slow down where you can see a front tire. if the tire moves back and forth while he is on the brakes, you have a loose strut rod or lower arm. also from my experience, the brackets that hold the front strut rods can come loose. but be careful when you tighten the three 10 mm bolts that hold them to the chassis. they strip easy. torque those down to about 45 ft. lbs.