Front Brakes Dragging, Already Replaced....

Vehicle: 2001 Tacoma 2wd, 2.4L

My last set of brake pads only got about 10k miles on them before the wear indicator started screeching. Evidently my brakes had been dragging, not sure for how long. I replaced my front drivers side caliper when I replaced the pads 10k miles ago, and I thought now the passenger side caliper was sticking, so I just replaced it, put in new pads, bled the system, and it still drags. It is just the front wheels that are dragging. It takes two hands to turn the hub. When I take off the caliper it spins freely.
So yesterday I replaced the master cylinder, bled the lines in the proper order and the proportioning valve (rear passenger, rear drivers, front passenger, front drivers, proportioning valve). Still dragging!
Today I did some more troubleshooting. I'm getting flow to the calipers. If I open the bleed valve I get a slow gravity flow. When I flip up the caliper and watch the piston while my helper presses the brake it appears to be working properly. It extends when the brake is pressed and retracts slightly when they let off the brake.
I also tried loosening the master cylinder from the brake booster to see if perhaps the push rod was an issue. I loosened the MC as far as I could without taking the two bolts all the way off, I'd say about 8 mm. Still no bueno. WTF?
Can anyone help me out? My thoughts are bad brake hoses (I ordered two which should be in Wednesday next week just in case). Brake booster? Proportioning valve? I'm tired of throwing parts at this thing. Any help? I'm losing sleep over this thing beating me.

Thanks!

 

Do the calipers mount on slider pins? I've seen corroded/frozen ones create havoc on other marquees.

 

Yes they do. They are new calipers and slide smoothly. I like the signature BTW!

 

Does your drake pedal retract all the way to the top? Or is the push rod snug against the brake pedal? There needs to be a little clearance there or the system will gradually build pressure on the front brakes. The brake pedal return spring may cause it too if it lets the pedal rest too heavy on the rod. The rod clearance is usually adjustable.

 

The pedal does come all the way up. If I reach down and pull the brake pedal up, it doesn't come up anymore, maybe 1 or 2mm. Is the push rod the one that goes into the firewall and brakebooster?

 

Did you put antiseize on the edges of the brake pad backing plate and on the retention pins? They may slide easily now but bind up when trying to stop a rotating wheel.

 

Yes. I am 99% sure this is not a caliper issue. They are both new, slide smoothly, and the piston extends and retracts when I watch it.

 

Yes, the rod that goes thru the firewall.

 

Looking at the FSM on the vehicle it says, in bold, not to adjust that. Should I really be messing with it? Is it possible for that to get out of whack without me touching it?

 

It needs a little clearance between the pedal arm & push rod or you'll have problems like you describe.

 

Should I be adjusting this rod on the brake pedal side of the firewall or on the master cylinder side of the firewall? There are definitely instructions on how to do it where it meets the MC, but not for the pedal side. From what I can see, adjusting the nut on the pedal side only adjusts the height of the brake pedal, it doesn't actually create a gap b/w pedal and push rod. The pedal assembly is resting on the adjustable nut. Am I missing something?

 

Also, if the brakes were never releasing, wouldn't that affect the rear brakes as well? Right now it's only the front brakes that are dragging.

 

I just played with the adjusting rod behind the brake pedal. I went all the way in both directions and no difference either way.
Any other ideas? Troubleshooting tips?
Another note: even when I open the bleed screw on the caliper there is no noticeable improvement. I would think this would relieve any pressure that may be stuck in caliper but the fluid flows out slowly and the brakes still drag.

 

After you adj. the clearance you have to drive it around a while to see if it stops the pressure build-up.

 

I turned the car on and let it run for about 5 mins while I tested the brakes and hubs. No change.