So I've been combating this for awhile. Hit the brakes, firm, then spongy, then hard pull to the left, followed by a mean wiggle. I've been throwing parts at it to no avail. First came steel braided lines. No dice. Next Calipers, pads and rotors. A little better, but not quite. So then I swapped in a new master cylinder, stiffer but still the weird feeling followed by the sharp pull to the left. At this point I'm not sure what to do. ABS? Proportioning valve? I'm lost. I fell like this--->

 

Just pray tell are you working on???

4 Wheel disc brakes??

Could be a tire issue

could be suspension

how your vehicle is loaded

could also be the road and how it is pitched.

At what speeds does this happen??

ABS brakes can do interesting things

 

It's a 98 4runner so front disk rear drum.

Not a tire issue tires originally didn't cause the issue and rotating does nothing.

Suspension might be playing a part but there is a pedal feel issue.

Load is static and changes did not incite the problem.

Not the road it happens everywhere.

Happens at all speeds.

It honestly feels like only the left front initially grabs, as it pulls the wheel hard left to the tune of 80 degrees. Then everything else catches up. It's not the caliper as I changed calipers and it in no way effected this issue.

 

If your tires are out of balance, you wouldn't necessarily notice if you put the wheel in the air and spin it, but it would cause wobble and possibly something weird with your peddle.

Just curious, did you use dot3 brake fluid?
Is your cylinder/brake line bleed properly?
How far did you take your new brake line(s)?

 

Hahaha. By rotating tires I mean front to back not spinning the wheel.

One of the techs at work said its air in the abs that can't be manually bled out. Makes the most sense so I'll go that route first. .

 

Your keeping the rear brakes adjusted up by using the E-Brake.

that could be part of the issue if your not.

I have felt ABS brakes pedal firm computer senses a wheel lock pedal feels like stepping on a plum.

Then you get that shudder .

I hate ABS Brakes.

Using a vacuum bleeder I have no problem bleeding them.

 

Check for a leaking rear axle seal. When the shoes are oil soaked they will cause the rear brake to seize and shake the whole truck. One side grabbing will cause the truck to pull to one side. You may see oil running down the inside of the rear wheels or you may need to pull the drum. A quick way to check is drive the truck for a while and then park it, check for a heat difference between the left and right drum. A siezing drum will be scorching hot while a properly running brake will just be warm to hot.

 

Its not in the rear end. I've had blown axle seals before. They're pretty obvious. Its In the front. The abs is the only thing that makes sense and Monday I'll post the outcome for sure. The front left grabs hard enough to turn the wheel a good 80 degrees. The shudder is caused by the brakes balancing out and caster and kpa naturally returning steering to the direction of travel.