Rep Power: 224

2007 Civic Si. Bought with a broken timing chain. Fixed and took it for a drive. Brake pedal felt soft and found front right caliper was sticking. Replaced front calipers, rotors, and pads. Bled only the front afterwards. Brake pedal felt exactly the same. Took it down the road and got the brakes hot then bled the fronts again. No air came out. Took it down a gravel road and got ABS to kick in a handful of times. Bled all four corners this time. A small air bubble from the front left, nothing from the other three. No change in pedal feel. Took it down the gravel road again then blead all four corners. No air, pedal still the same. Decided to replace the driver rear caliper because the bleed valve snapped (I was bleeding from the brake hose before). Bled all four corners a couple times. Pedal still exactly the same. At this point I have gone through 32-48 fl oz of brake fluid and have made basically no improvement.

This is far from my first time bleeding brakes and I have never experienced this before, even on a completely empty system. At this point, I think there's air trapped in the ABS module that I cannot get out. Service manual does have a note under the ABS module replacement saying if the brakes feel soft afterwards, there may be air trapped in the modulator and then induced into the normal brake system during modulation. It then says to bleed them again. I assume the previous owner let the brake fluid reservoir get too low and got some air in the system. The passenger side rear caliper had been replaced at some point. I guess my plan at this point is to keep getting ABS to engage on the gravel road then bleed all four corners. I'm sick and tired of jacking it up, removing all four tires, having my wife help me bleed, putting the tires back on, then driving 20 feet down the road and realize the pedal still feels terrible.

Any input is welcome.

 
Rep Power: 367

they usually recommend bench bleeding ABS module.
do we have brake pedal adjustments?

 
Rep Power: 224

Bench bleeding the ABS module is not mentioned in the service manual, just bleeding multiple times. There is a pedal adjustment but I don't think that's the issue. Pedal goes basically to the floor before it does something.

 
Rep Power: 222

Can you hot wire the modulator to force the bubbles out?

 
Rep Power: 224

I will have to look at the wiring. I assume there is an internal relay the module controls to enable the pump. I did check my scanner, it is not smart enough to turn it on.

 
Rep Power: 222

Got a mechanic buddy that can take one home?

 
Rep Power: 224

I am "the mechanic" in my friends/family group. I can't think of anyone that would have one.

Looks like there is an internal relay that controls the pump. However, it also looks like the electronic portion may separate from the hydraulic portion. That could allow me to power the pump directly. We will see.

 
Rep Power: 222

Might have to spoof a 5v signal, hopefully you can just hit it with 12v

 
Rep Power: 224

Glanced at the pump/module. Module can be removed but there is basically no clearance without disconnecting brake lines. Thinking about it some more, running the pump won't active the valves as well so I'm not sure if that would help. I did try getting the front off the ground, getting up to speed and hitting the brakes hoping for ABS engagement. With the rear wheels not moving this should active the rear ABS valves. I can get the fronts to activate fairly easily on the gravel road but I'm not sure the rears are ever locking up. At first traction control wouldn't let me above ~11 mph. I disabled VSA and it let me go faster, but I never felt ABS engage. If I'm honest, I had low hopes that this would work.

Having difficulty finding time to work on it. Hopefully this evening I can take a few trips down the gravel road again then bleed afterwards. The sun setting at 6:30 PM really makes it hard to stay motivated.

 
Rep Power: 224

Finally got to the bottom of it. I appreciate everyone's input.

It rained last night so the roads were wet this morning. Took it for a drive trying to get ABS to kick in on the rear. Got home and bled all four corners again, no air. Started it back up and drove through the grass in my yard. It was very slick due to still being wet. Bled just the rears afterwards, no air. Noticed the right rear rotor wasn't as clean at the left side even after all this hard braking. Pumped up both rear tires to near max PSI to try to help facilitate a lockup and ABS engagement. Had my wife take a video so I could see if ABS was ever kicking in on the right rear while driving on the wet grass. It was not. Back into the garage it went.

Took the right rear tire off for what seemed like the 87th time. Noticed the park brake lever was fully engaged but the wheel was free spinning. When pushing the brake pedal the wheel would eventually lock up but seemed delayed. Suspicious. Pulled the caliper off and used a screwdriver to spin the piston. No issues there, it wasn't seized. Had my wife push the brake pedal. Piston would come out a bit then go all the way back in when she released the pedal. Seems the ratcheting mechanism was not working. Mashing the brake pedal a few times quickly, I eventually got the piston to stay out. Screwed it back in enough to clear the brake pads and put everything back together. Pulled out of the garage and hit the brakes at the end of the driveway. Halleluiah, finally some firm brakes. Went back down the gravel road to get ABS to engage again then bled the brakes one more time just to see if any air worked it's way out. Nothing.

In summary, the only additional air I ever got out after replacing three of the four calipers was a small bubble from the front left. And that was the first time I bled after getting ABS to kick in. I went through 64+ fl oz of brake fluid while bleeding during this entire ordeal. The soft pedal was solely the cause of the ratcheting mechanism on the right rear not stopping the piston from going all the way back in. This meant when I pressed the brake pedal the soft feeling was the piston pushing a few millimeters out until it got to the pad (if it even was). Admittedly, I should have noticed and investigated the right rear brake a lot sooner. If it were a car I planned on keeping, I would have replaced the rear calipers a long time ago and never would have had the issue. Oh well. I'm just relieved to finally be done messing with the brakes on this thing.

 
Rep Power: 367

woah, glad you found the issue!
That was an unexpected part failure...

 
Rep Power: 222

Glad you figured it out dude!