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Discussion Starter #1
I just did a rotor / pad change on my 01 AC. This is not the first time I've done the brakes on this truck, but it's the first time I've had this problem....

Old parts removed:
Brembo cross drilled rotors / Wagner Thermo-Quiet ceramics

New parts installed:
Brembo non-cross drilled OE replacement rotors
Hawk Performance LTS pads (new shims installed)

I had the cross drilled rotors turned when I installed the Wagner pads (I know, big mistake...they're already shuddering again. It's the first time in 30 years I tried turning my rotors instead of replacing them. I won't make that mistake again.). Anyway, I just did the brakes about 3000 miles ago, so it's fresh in my memory.

So, when I pulled the truck into my garage to do the brakes this past weekend, the pedal was nice and firm. I removed the pads, pushed the pistons back in the bores with a C-clamp (using the old pads to push against), pulled the caliper and swung it out of the way long enough to remove the old rotor, and put the new one in place, then put the caliper back on, and torqued the bolts to spec. I reinstalled the new pads, put a thin film of grease on the retaining pins, buttoned everything up, and moved on to the other side. At no time did I open up the system and let air in anywhere.

After getting everthing back together, I got in the truck, started it, and the pedal was WAY softer than before. I thought that maybe the pads needed to be bedded in, so I went ahead and did the break in procedure per the instructions included with the Hawk pads. The brakes do indeed stop the truck, but the pedal is much spongier than it has ever been, and I've had the truck for 10 years. With the truck running, I can push the pedal to the floor...I've got to put some force on it, but it will go to the floor. It didn't do that before. With the engine off, and the vacuum bled off, I can press the pedal down about 1 - 1.5 inches, and it feels like I'm against a spring, then it gets really firm, and won't go any further. The problem is, as soon as I start the engine, and the power booster kicks in, it'll go to the floor again.

Even though I didn't crack open any lines, to me, this is classic "air in the system" symptoms, so I bled both fronts anyway....I got no air out of the system, and it made no change. I also re-adusted the rear drums...no change there either. I'm at a loss here....the only two things I can think of is that in the process of pushing the pistons back in the caliper, they didn't go back in square, and I scratched them, and now have some leakage going past the seal (I'm going to pull the pads, and gently pull back the rubber boot to see if fluid is getting past the seal tomorrow). It's either that, or something screwy happend when the fluid was pushed back up the system, which would be strange, because it's the same thing I did last time, and it worked just fine.

Before I start pulling my hair out, does anyone have a suggestion on what it could be? Seriously, it was fine when I pulled the front brakes off, and not right an hour later....it had to be something that I did. I just can't figure it out. Sorry for the long post, but I wanted to give enough info to help diagnose the problem.
 

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Mech. Engr. / Mechanic
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I can't help with your specific problem, but just for future reference, when bleeding brakes, it's safer to clamp off the line above the caliper and open the bleeder before pushing the pistons back in. This eliminates the problem with pushing brake flued backwards through your anti-lock brake system. It's been known to cause problems in a lot of vehicles, maybe not the Tundra, but it is a lot safer method.
 

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Discussion Starter #3
Good point. My truck doesn't have ABS though, so I'm still in a pickle.
 

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I would check the master cylinder for a leak as well. I had an master cylinder gasket fail on another car and it exibited the same symptoms as air in the lines. Check the firewall directly below the master cylinder to see if there is any residue.
 

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You may have pumped junk back into the master that caused it to leak. I used to live on the coast and brake fluid didn't
last but a few years before getting very contaminated.
 

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^^^^ I agree!!! I opened the cap on the master cylinder and the fluid almost spilled out when I pressed the pistons back. I siphoned some fluid out before closing the cap. You may have damaged some seals on the master cyl.
 

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I can't help with your specific problem, but just for future reference, when bleeding brakes, it's safer to clamp off the line above the caliper and open the bleeder before pushing the pistons back in. This eliminates the problem with pushing brake flued backwards through your anti-lock brake system. It's been known to cause problems in a lot of vehicles, maybe not the Tundra, but it is a lot safer method.
You don't want to "clamp off the line" unless you are going to replace them afterwards. Clamping the rubber lines can damage/weaken them leading to a line failure. Just open the bleeder screw and have a bleeder hose connected to catch the fluid and prevent air from getting into the system.
 
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