Front Brakes Dragging, Troubleshooting Steps

[Rusty Shakelford]

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!

 

[WiskyT]

Disc brakes will always drag a little bit, that's why old school drag racers used drums.

Is one side dragging more than the other, is it harder to turn one side by hand?

With the new pads on, drive it for a few days and THEN see if the wheels are hard to turn. New pads need to bed in a bit and may be dragging if all you did was install them and then try to turn the hubs.

I don't think you have an hydraulic problem. My first guess would have been frozen calipers which is very common, but you changed them. The lines and bleeding aren't going to cause your problem. It was a good idea to bleed them anyway as maintenance so that was not a wasted effort.

Calipers slide back and forth on the mounting rails and the bolts which have a bearing surface. The bolts typically have an unthreaded portion, that is the bearing surface. All bearing surfaces must be free of rust and the crud that builds up on them. The bolts get tossed in the trash. If they are cruddy and you clean them up, the surface finish gets removed and they corrode up quickly. Get new caliper bolts since they are cheap and 15 year-old caliper bolts are more than likely crusty with corrosion and brake dust.

Get an aggressive Scotch pad and clean the mounting rails and the mating surface on the calipers. Use brake clean to keep things wet to keep the dust down. Once you have new bolts, ASSuming your old bolts were stained and corroded, apply SILICON grease MADE FOR BRAKES!!! Regular wheel bearing grease will cook and make crud from the high heat and do the exact opposite of what you want. The silicon brake grease keeps the bearing surfaces lubes and prevents corrosion, keeping things sliding along. Apply it liberally, but not so much that it can come off onto the friction surfaces. The calipers usually have rubber seals that the pins go through, this is to keep the grease in, and the dirt out.

Pads can vary in quality and driving can vary in brake demand. If you are pulling a heavy landscape trailer and one of your foremen who doesn't care about your truck does most of the driving, and you buy standard pads, you can wear them out in 10k miles. I would get the $50.00 pads instead of the $30.00 pads if you do normal driving. I drive pretty "normal" mostly sceondary roads and when I turn my lease Taco's in with 35k miles, the brakes still have plenty of wear left on them.

 

[Rusty Shakelford]

Disc brakes will always drag a little bit, that's why old school drag racers used drums.

Is one side dragging more than the other, is it harder to turn one side by hand?

With the new pads on, drive it for a few days and THEN see if the wheels are hard to turn. New pads need to bed in a bit and may be dragging if all you did was install them and then try to turn the hubs.

I don't think you have an hydraulic problem. My first guess would have been frozen calipers which is very common, but you changed them. The lines and bleeding aren't going to cause your problem. It was a good idea to bleed them anyway as maintenance so that was not a wasted effort.

Calipers slide back and forth on the mounting rails and the bolts which have a bearing surface. The bolts typically have an unthreaded portion, that is the bearing surface. All bearing surfaces must be free of rust and the crud that builds up on them. The bolts get tossed in the trash. If they are cruddy and you clean them up, the surface finish gets removed and they corrode up quickly. Get new caliper bolts since they are cheap and 15 year-old caliper bolts are more than likely crusty with corrosion and brake dust.

Get an aggressive Scotch pad and clean the mounting rails and the mating surface on the calipers. Use brake clean to keep things wet to keep the dust down. Once you have new bolts, ASSuming your old bolts were stained and corroded, apply SILICON grease MADE FOR BRAKES!!! Regular wheel bearing grease will cook and make crud from the high heat and do the exact opposite of what you want. The silicon brake grease keeps the bearing surfaces lubes and prevents corrosion, keeping things sliding along. Apply it liberally, but not so much that it can come off onto the friction surfaces. The calipers usually have rubber seals that the pins go through, this is to keep the grease in, and the dirt out.

Pads can vary in quality and driving can vary in brake demand. If you are pulling a heavy landscape trailer and one of your foremen who doesn't care about your truck does most of the driving, and you buy standard pads, you can wear them out in 10k miles. I would get the $50.00 pads instead of the $30.00 pads if you do normal driving. I drive pretty "normal" mostly sceondary roads and when I turn my lease Taco's in with 35k miles, the brakes still have plenty of wear left on them.

The slides are new. They came with the new calipers. I greased everything. The calipers work fine and slide smoothly. The piston extends and retracts fine. I don't think this is normal drag. The rotors get so hot after a lap around the block that I can't even touch them. It takes two hands to turn the front rotors. Is that normal?

 

[WiskyT]

The slides are new. They came with the new calipers. I greased everything. The calipers work fine and slide smoothly. The piston extends and retracts fine. I don't think this is normal drag. The rotors get so hot after a lap around the block that I can't even touch them. It takes two hands to turn the front rotors. Is that normal?

No, it's not normal. If the truck has ABS, maybe it has something to do with that. You've changed everything else. I don't see what changing the lines will do. If you are talking about the hoses that go to the calipers, okay, but what about all of the rigid lines that go to them? Are you talking about bending a whole set of rigid lines for the thing?

I don't know if an ABS problem could cause BOTH calipers to drag an equal amount, but most if not all ABS problems will put up a code or two and the idiot light on the dash should be on.

 

[Rusty Shakelford]

No, it's not normal. If the truck has ABS, maybe it has something to do with that. You've changed everything else. I don't see what changing the lines will do. If you are talking about the hoses that go to the calipers, okay, but what about all of the rigid lines that go to them? Are you talking about bending a whole set of rigid lines for the thing?

I don't know if an ABS problem could cause BOTH calipers to drag an equal amount, but most if not all ABS problems will put up a code or two and the idiot light on the dash should be on.

I meant hoses, not lines.
No lights on the dash. Haven't run it for codes, but not sure if I would get a code without a check engine or BRAKE dash light on. Would I?