Just replaced the front brake pads....

on my 2004 Taco. Had to take the passenger side caliper off so I got some air in the lines. I've bled them about 10 times now. Brake fluid level is good (had to add some naturally) and the brake pedal is solid...until I start the engine. Once the engine is running the brake pedal goes to the floor. So I bleed them again and the cycle repeats and it doesn't seem to be getting any better. I have no idea what could be causing this. Any suggestions would be appreciated.

 

You have air in the system. If the level in the reservoir got too low you could have air in the MC. Depending on the method you used to bleed the brakes you may have sucked air back into the bleeder.
Please describe the method you used to bleed your system. 2 person, speed bleeder, ECT.
Also, do you have ABS?

 

I assume you meant "the brake pedal goes to the floor when I step on it..."

 

Yes that is correct.

 

No need to bleed this all fancy with a Vacula vaccum machine or anything, bleed with engine off only, you can actually bleed all by yourself! you need a clear hose with a check valve for the bleeder screw. This type device can be had for 20dollhairs or less at any cycle gear-motorcycle place theres a spring loaded ball in the check valve to prevent air coming back in, and dont forget to keep the master cylinder full the whole time you do this. You should rebleed all wheels starting from back to front to remove all the air, and the device Im talking about can be used on all these bleeders. Once the rears are bled clean, don't forget to bleed the load proportion valve near the gas tank, its often overlooked. Good luck

 

Why did you have to disconnect the passenger brake line?
This could also be a brake booster issue. Did you disconnect the vacuum line?

 

I've had the same thing happen when replacing brake pads.Even though the bleed valve was never opened.
Check the rear brake adjustment to see it's adjusted properly. Check the emergency brake function before you take the truck on the street.
Try accelerating the truck S L O W L Y back and forth and step on the brake after five feet or so. See if the truck stops as it should. No pull to either side. You can lock up the wheels if you wanted to.
There is a chance that the system has been bled properly. The new pads just aren't seated.
The brake pedal should return to its normal position after a few brake applications from 45 MPH to about 5 MPH. Don't come to a FULL stop. Just a rolling stop. Drive and let the brakes cool off again. Then stop from 45 to about 5 MPH.
Follow this advice at your own risk! Maybe there is air in the system. I don't know.

 

The brakes operated fine before I changed the front brake pads, no issues. I had to remove the passenger side caliper because on one side the cylinders were stuck out. So much so that it wore that pad down to the metal and all other pads were actually fine but I changed them anyway. While working on the caliper I wasn't paying attention to the fluid level and the whole reservoir drained out. I worked on it again today. I bled every line while my friend helped me by pumping the brake pedal as needed. Still the same issue. Pedal was solid while engine was not running. Start the engine, push the brake pedal and it will stop, but with continued pressure on it (like at a stop sign or red light) the pedal will creep to the floor. So we decided to go a step further. I got some clear tubing and ran it first from the driver side bleed valve back to the reservoir to make sort of a closed loop system as we felt we may have air in the master cylinder. Cracked open the bleed valve and pumped the brake pedal about 75 times or so. I did see some tiny air bubbles during this and we stopped once we had a steady oil flow with no air bubbles, again about 75 times. We repeated the process for the front passenger side. After that we felt pretty good about it as we had nice clear fluid with no bubbles. Started the engine and the same exact problem was still there except now my brake light is lit on the dash (it wasn't before) so there is definitely an issue here. I'm thinking maybe there is air trapped in the ABS module? Is that notoriously difficult to purge of air?

 

Yes the truck has ABS. See my previous comment to see what we did today to it.

 

Did the pedal ever go all the way to the floor? Might have torn the seal in the MC if it ran dry that first time. The booster check valve could also have failed and isn't purging air before it enters the MC.

The only other thing I can think of is that you might have gotten some bubbles in the ABS module. That thing's got lots of valves, nooks, and crannies for air to get trapped in.

My rig doesn't have ABS so I've never worked on one in a taco

 

Since you let the master cylinder empty out, you definitely got air into the master cylinder. There is a bleed procedure for this in the FSM and it's not what you did.

Once you've bled the master cylinder, have your ignition key in the "on" position to start bleeding the rest of the system. Start with the passenger side rear wheel, then the driver side rear wheel, then the passenger side front wheel, and then the driver side front wheel. If you have an LSPV (Load Sensing Proportioning Valve) bleed that last.

After all that, you should be good to go.

 

Good information here.

The passenger rear, driver rear, passenger front, driver front procedure ensures a complete flush.

Also; when we continuously pump without stopping to bleed our brakes, the air can be sucked back up the line before actually being pushed out the bleeder valves by the hydraulic pressure backing the fluid.

So ensure you're not only following the above steps that @Luv my yota and @Timmah! posted, but also pump thrice and hold for at least two seconds (one-one thousand, two-one thousand) and repeat approximately 16 times (which isn't painstaking, though neither a marathon).

Between about three sets of pumping, take a break by refilling the Brake Master Cylinder. Top it off to just below overflowing; this will ensure you're unlikely to drain all the fluid.

• Be sure not to overtighten the bleeder valves; hand tight and then a snug check is fine.
• Also; be sure the hose you're attaching is attached snugly; a hose too large will allow air to seep into the bleeding line.
• When each brake is bled, use a crescent wrench to tighten the bleeder valves while the bleeder line is still attached to ensure only fluid is the last thing that populates the valve, not air.

 

This should be sticky. From my understanding the first gens don't have separate front & rear brake line systems. I have been trying to bleed the fronts since all I did were the fronts (pads, rotors, calipers).... Bled 'em twice, spongy. Did some research & came upon the "all in one" braking system & this LSPV, which I'll have to see if I have. Anywho, I was just about to start a new thread asking if this might be the error of my ways & if I do have the LSPV, where it falls in the sequence. Then I vaguely remembered that I happened upon this thread in the midnight hour last night, or would that be this morning.... This should be sticky.... Just sayin'....
I didn't see anything in the sticky DIY list & the videos regarding brakes are just rotors & pads = no bleeding....
Either way, thank you.... Hopefully this solves my issues, well, this one anyway....