Head scratcher....strange goings on with brakes

[santacarl]

Hey All,

Well.....01 SSEi got a brake job after exhibiting a low brake pedal....had all the symptoms of a bad master cylinder....so while I was at it I just went ahead and threw on rotors and pads to include new bolts and boots

Installed new rotors and pads earlier this week....today a NEW Centric MC....bench bled it...installed it....bled out all the old brake fluid in the lines. Hopped in the car...pumped the pedal a couple of time and Yay....nice firm and high pedal.....

Fired up the engine to take it for a test run. Hit the brake pedal to put it into gear and the pedal goes almost all the way to the floor....maybe an inch from the floor. Pumped them several time with no change....Did the old driveway test...forward a few yards....back up a few yards.....I was able to stop and the pedal once at the bottom stays firm....so I took it out for a short spin.... Stops without giving me a 'pucker' factor off the scale....but the pedal is still an inch off the floor.... Just about the same as before the brake job....

Now, here's the kicker.....after thinking on it a bit and remembering that I had a good firm pedal right after bleeding and without the engine running I went back and hit the pedal without the engine running.....again FIRM and FULL pedal.... Cranked the engine..hit the pedal and back almost to the floor she goes....

Does anyone have any idea what's causing this?

Thanx

[AJT2004]

I think your problem is still trapped air, what procedure are you using to bleed the system?
Did you inspect the flexible lines for damage?
A hard brake pedal with the engine off is due to no vacuum at the booster.

[santacarl]

I think your problem is still trapped air, what procedure are you using to bleed the system?
Did you inspect the flexible lines for damage?
A hard brake pedal with the engine off is due to no vacuum at the booster.

Thanks for the response "AJT".....

Well...as I mentioned I bench bled the MC first and there was no air residing in the MC after I finished.... Then for the calipers I used a bleeder bottle and pushed fluid into it with the pedal....The bottle prevents air from being sucked back into the system and I was able to monitor the fluid color to tell that new fluid had traveled the entire length from MC to caliper....

Checked all the lines and calipers....no leaks any place....in fact the old system was still full of fluid and I hadn't added any fluid in probably close to a year so I know there wasn't a leak any place.

I agree it 'sounds' like trapped air but it was acting this same way before I replaced all the parts and the system so having the same symptoms leads me to believe it's not trapped air.... As I mentioned, there was no leaking at all before the new parts and fluid level was topped off....So I doubt it was trapped air as the system started with the low pedal after having run many, many miles since I last replaced the pads and fluid..... It just recently started this low pedal thing.....so I thought surely it was a MC leaking internally...... I suppose I could go back and re-bleed using a helper instead of a bleed bottle but I don't think it will change much...

I guess the vacuum impacting the booster when running is a sign that the booster is ok.....But I did notice there seems to be more sound when I press the pedal.....sounds like an old Plymouth I used to have....sort of a schussing sound when the pedal is depressed....I don't recall it being so pronounced in the past....but that could just be the fact that there's more pedal travel now....

[Erinyes]

I had an issue once where I just couldn't seem to eliminate all the air in the lines, no matter how I tried. Went to pretty great extremes to make sure I didn't have any seal leaks, pumped enough fluid through to fill three full systems. Finally gave up, took it to the local shop and had them power bleed the system. No more issues.

Not a great answer for you, but sometimes the best approach is to give up.

[santacarl]

I had an issue once where I just couldn't seem to eliminate all the air in the lines, no matter how I tried. Went to pretty great extremes to make sure I didn't have any seal leaks, pumped enough fluid through to fill three full systems. Finally gave up, took it to the local shop and had them power bleed the system. No more issues.

Not a great answer for you, but sometimes the best approach is to give up.

Thanks for the thought "Erinyes"
Yeah....I'm starting to think this one is above my 'paygrade'.... I do have a brake vacuum bleeder but it sometimes pulls air in around the cracked bleeder (around the threads).....So I thought I'd try the bleeder bottle this time.... I might try the vacuum to see if it makes a difference...it's sort of a poor man's power bleeder....doesn't rely on the master cylinder to push the fluid....if I can keep the bleeders from sucking in air......

But I keep thinking back to why I started this in the first place.....low pedal with no history of leaks or low fluid levels....I would think if there was an entry point for air I'd be seeing fluid leaks.....that's the part that has me stumped concerning possible air in the system...