brake saga continues
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Drifting
Joined: Jul 2003
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From: Orlando FL
brake saga continues
well, i did the gravity bleed...ran about 3/4 of a quart through the front and rear. nice clear fluid coming out all the bleeders with no more air. tightened everything back up and made sure the wheels stopped while it was still in the air. took it out for a test drive and it just doesn't feel "solid", which is very disappointing because i put on braided SS lines, new MC, bias spring, and all new fluid. it feels like it take 1/2 inch of pedal travel before anything starts to happen. i tried to lock it up doing about 15mph and i couldn't do it. spongy. so is it time to bleed it "the right way" with the open/close bleeder, "push, don't push" brake pedal game?
Team Owner
Joined: Aug 2000
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From: San Pedro CA
hm.
there should be an adjustment on the pedal itself. that will help take up some of the slack.
as for the mushies... I wonder if you have a bad caliper somewhere... they are getting older, you know...
there should be an adjustment on the pedal itself. that will help take up some of the slack.
as for the mushies... I wonder if you have a bad caliper somewhere... they are getting older, you know...
Team Owner
Joined: May 2002
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
And youre positive the reservior level didn't drop too low during bleeding?
If the M/C is new, and theres no fluid loss anywhere, its gotta be the bleed.
Tell us how it feels with the engine running vs off. If its solid with engine off, it could be an misadjustment in the brake booster pushrod.
If the M/C is new, and theres no fluid loss anywhere, its gotta be the bleed.
Tell us how it feels with the engine running vs off. If its solid with engine off, it could be an misadjustment in the brake booster pushrod.
Instructor
Joined: Jun 2003
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From: Orange Park Fl
Recently had the same symptons with similar part replacements. My Corrective action was to adjust the end of the rod that comes through the brake booster that pushes on the bias piston in the master cylinder. Turned it out 1 1/2 turns and it removed the pedal slack and mushiness because it more evenly applies the front and rear brakes. (You might be only stopping on the front brakes now) Unbolt the master cylynder from the booster and move it foward, Have someone slowly push the brake pedal down so that you can hold the rod and turn the adjustable end out. Repeat making ajustments as necessary until you feel the brakes are where you need them. One caution is that the there needs to be a minimal amount of slack in the pedal otherwise when the brakes get hot they will always be activated . Good Luck !
Thread Starter
Drifting
Joined: Jul 2003
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From: Orlando FL
well...the pedal is rock solid (like i think it should feel) with the engine off....then i turn it on and it goes to mush again....thurn it off and after 1 pump its solid again.....so that means the pushrod has to be adjusted?
and the fluid stayed at 1/2 of each reservior during the entire bleed...and the calipers should be good....i rebuilt those too during this process...caliper bore looks great....pistons were good....replaced all the rubber parts....it all fit like a glove....
so pushrod adjustment time??
and the fluid stayed at 1/2 of each reservior during the entire bleed...and the calipers should be good....i rebuilt those too during this process...caliper bore looks great....pistons were good....replaced all the rubber parts....it all fit like a glove....
so pushrod adjustment time??
Team Owner
Joined: May 2002
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Originally Posted by Orlando85UCFvette
so pushrod adjustment time??
Sounds like we may have found the culprit. Did you replace the booster or M/C? It doesn't make sense that the factory booster pushrod would have to be readjusted for a new m/c unless the new m/c piston isn't located the same as the original.If this is the case, there's nothing to compare the pushrod length to, you'll just have to guess and check. You might be able to move the m/c out of the way with the brake lines still on it... to adjust the pushrod quickly.
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Originally Posted by Orlando85UCFvette
well, i did the gravity bleed...ran about 3/4 of a quart through the front and rear. nice clear fluid coming out all the bleeders with no more air. tightened everything back up and made sure the wheels stopped while it was still in the air. took it out for a test drive and it just doesn't feel "solid", which is very disappointing because i put on braided SS lines, new MC, bias spring, and all new fluid. it feels like it take 1/2 inch of pedal travel before anything starts to happen. i tried to lock it up doing about 15mph and i couldn't do it. spongy. so is it time to bleed it "the right way" with the open/close bleeder, "push, don't push" brake pedal game?
3/4 of quart for both front and rear brakes is no way near enough! Gravity bleed is the "right way" provided you use enough fluid! And you have enough patience!Push, don"t push works too, but it is more hit or miss!
Sorry you are having trouble! BTW, a half inch of travel at the top of the pedal is not a serious problem! This allows some light foot pressure to not activate the brakes and cause wear
Jack
Last edited by jackdaroofer; Nov 13, 2004 at 07:54 PM.
Team Owner
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From: SE NY
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Hmmm, I notice a little of your symptom after installing a new MC and bleeding all the cylinders.
Though the effect isn't enough to be a problem it might be worth a try to bring up the pedal just a tad.
I should think you could check the pushrod adjustment by spinning a front wheel to see if is still free.
Though the effect isn't enough to be a problem it might be worth a try to bring up the pedal just a tad.
I should think you could check the pushrod adjustment by spinning a front wheel to see if is still free.
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Le Mans Master
Joined: Feb 2000
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From: Kempner Texas
When I replaced my booster earlier this year my pedal had too much travel before the brakes would engage.
The booster rod would not adjust outward, so I shimmed it with small washers. I tired three at first, but the brakes were dragging, so I removed one - leaving two in place - and that did the trick.
Jake
The booster rod would not adjust outward, so I shimmed it with small washers. I tired three at first, but the brakes were dragging, so I removed one - leaving two in place - and that did the trick.
Jake
Instructor
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From: Orange Park Fl
You can probably go and have the system vacuum bled if time is and issue,
If not:
I would bleed the system with the push don't push method. Follow RR / RL / FR /FL. Repeat this at least 4X around to get the air out of the ABS. If you don't have a solid pedal after that, Adjust the rod as mentioned above. You will need to drive it for a period after that to get the fluid hot. (I braked numerous times until I could get the ABS to trigger during stops). Then bleed the system again. The solid / mushy pedal with the car on and off is just the booster not assisting.
If you want to call, send me your E mail address and i will send back my phone number.
If not:
I would bleed the system with the push don't push method. Follow RR / RL / FR /FL. Repeat this at least 4X around to get the air out of the ABS. If you don't have a solid pedal after that, Adjust the rod as mentioned above. You will need to drive it for a period after that to get the fluid hot. (I braked numerous times until I could get the ABS to trigger during stops). Then bleed the system again. The solid / mushy pedal with the car on and off is just the booster not assisting.
If you want to call, send me your E mail address and i will send back my phone number.
Thread Starter
Drifting
Joined: Jul 2003
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From: Orlando FL
Originally Posted by jackdaroofer
3/4 of quart for both front and rear brakes is no way near enough! Gravity bleed is the "right way" provided you use enough fluid! And you have enough patience!Jack
no no....3/4 for the front and 3/4 for the rear. maybe even a lil more. tomorrow morning i will try the push rod adjustment...this isn't just something to "live with". its not right yet...like i said...from 15 mph i tried to make the tires chirp with a full on slamming fo the pedal, and they didn't. more to come tommorow.........
Drifting
Joined: Mar 2002
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From: Thomson Georgia
Bleed, Bleed, Bleed.
You have air trapped. Make sure you have the ABS shuttle centered. If it isn't, it will not bleed right, and you will have trapped air. 1/2 of travel before pedal engagement is not a problem, if you readjust and go too far, the brakes will not release completely and after a few applies, the brakes will start dragging. Not good.
Bleed the system down via pedal pressure method. Slow pumps till full pedal (usually 2-3), bleed slowly with foot on pedal, close, repeat until clear. You will refill each reservoir a couple of times, it only takes one tiny bubble to have a spongy pedal. If you pump the pedal too fast, causes shuttle valve over center on the ABS and a reset.
Thread on brake conversion with bleeding info
http://forums.corvetteforum.com/showthread.php?t=710058
You have air trapped. Make sure you have the ABS shuttle centered. If it isn't, it will not bleed right, and you will have trapped air. 1/2 of travel before pedal engagement is not a problem, if you readjust and go too far, the brakes will not release completely and after a few applies, the brakes will start dragging. Not good.
Bleed the system down via pedal pressure method. Slow pumps till full pedal (usually 2-3), bleed slowly with foot on pedal, close, repeat until clear. You will refill each reservoir a couple of times, it only takes one tiny bubble to have a spongy pedal. If you pump the pedal too fast, causes shuttle valve over center on the ABS and a reset.
Thread on brake conversion with bleeding info
http://forums.corvetteforum.com/showthread.php?t=710058
Last edited by johnnyevans; Nov 14, 2004 at 12:45 AM.
Thread Starter
Drifting
Joined: Jul 2003
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From: Orlando FL
well...i turned the adjustment rod out a bit, then back again a lil because the pads were dragging...and i got it up to 30MPH and SLAMMED the brakes and it stopped real hard, but no skid. one thing i wonder about it the new bias spring that i installed in the MC. its supposed to move more power to the rear before the fronts...better braking (or so it says). would that lead to "better" braking and less skidding? its not like i want the car to lock up, but that to me is testament that the brakes are clamping down as hard as they can. and i know it will lock, cuz without ABS i've done it in serious conditions.
thanks for all the help here......i just wanna be sure this is right.
thanks for all the help here......i just wanna be sure this is right.
Team Owner
Joined: May 2002
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
You should always be able to lockup the brakes. Are your tires brand new? A verrry rough street surface? Enough engine vacuum at idle?
What's the condition of the pads & rotors? Douche the rotors with brake cleaner, turn them if necessary, sand and bed the pads.
This seems like we're splitting hairs over small things, when there's something else going on. When the brakes dragged, where you able to lock em up? (maybe a tad more adjustment outward will help) Maybe it is just a bunch of small things adding up.
Sounds like my luck. Glad it's not my car this time!
What's the condition of the pads & rotors? Douche the rotors with brake cleaner, turn them if necessary, sand and bed the pads.
This seems like we're splitting hairs over small things, when there's something else going on. When the brakes dragged, where you able to lock em up? (maybe a tad more adjustment outward will help) Maybe it is just a bunch of small things adding up.
Sounds like my luck. Glad it's not my car this time!
Last edited by CentralCoaster; Nov 14, 2004 at 03:09 PM.
Burning Brakes
Joined: Jul 2003
Posts: 873
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From: Whittier ca
I've been fighting the same problem for months. As of today, I may have found MY problem 
(daily driving this week will tell). I have been figuring to rebuild the calipers next weekend, but decided to bleed all four corners (again) this weekend after checking the endplay on the rear hubs. I replaced the bleed valves with spped bleeders some months ago, but they seemed to leak, so I changed them back to stockers. After trying to bleed with a vacuum pump and constantly getting air, with some help doing the pump, hold, bleed method, no air. By off chance, I had the helper put moderate pressure on the pedal and, WTF, brake fluid came up through the valve! What I found was, at some point, both caliper seats had a low spot, like a previous beed valve was out of center. This cause fluid to bypass the seal and, bingo, a bunch of air. I don't know if there is a "replacement" seat for the calipers, but I ended up using a hone from a Dremel tool, a hand drill and a plastic MC bench bleed adapter as a guide and honed a new seat. Went for a test drive and what a difference!
It might be worth you while to check it out.
Good luck!
(daily driving this week will tell). I have been figuring to rebuild the calipers next weekend, but decided to bleed all four corners (again) this weekend after checking the endplay on the rear hubs. I replaced the bleed valves with spped bleeders some months ago, but they seemed to leak, so I changed them back to stockers. After trying to bleed with a vacuum pump and constantly getting air, with some help doing the pump, hold, bleed method, no air. By off chance, I had the helper put moderate pressure on the pedal and, WTF, brake fluid came up through the valve! What I found was, at some point, both caliper seats had a low spot, like a previous beed valve was out of center. This cause fluid to bypass the seal and, bingo, a bunch of air. I don't know if there is a "replacement" seat for the calipers, but I ended up using a hone from a Dremel tool, a hand drill and a plastic MC bench bleed adapter as a guide and honed a new seat. Went for a test drive and what a difference!It might be worth you while to check it out.
Good luck!