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Author Topic:   BRAKES?
DangerZoneRacing
Dirt Maniac

Total posts: 176
posted July 07, 2005 09:06 PM  
I have a major problem that needs to be fixed before this Saturday night. Last year I lost alot of brake peddle and bled the brakes and no change, but still had brakes. Last race day 2 laps into the feature I think I lost them all. They still worked but wouldnt grab enuff. The peddle would go almost to the floor, When stopped I would press the peddle and put into gear and it would hold till I hit the gas. When I burp the gas it'll lurch foeward then stop. I have put a brand new master cylinder on and bled the whole system till all the old fluid is out and still goes to floor. By the way this is a complete stock system in a 81 cutlass. Could my front calipers maybe have took a dump? I cant go get any replacement racing parts cuz we dont have access to anything like that locally, I would have to order that and I would be screwed for this weekend. I dont want to sit this raceday out cuz I'm 2nd in points and only 4 points out of 1st. HELP please.

speedwrench
Dirt Roller

Total posts: 16
posted July 07, 2005 09:17 PM  
Did you check the mastercylinder? sounds like a internal leak.Are you getting good pressure at the calipers and rear cylinders? You'll need to see 500 to a 1000psi depending on the mastercylinder ID.

speedwrench
Dirt Roller

Total posts: 16
posted July 07, 2005 09:20 PM  
Did you check the mastercylinder? sounds like a internal leak.Are you getting good pressure at the calipers and rear cylinders? You'll need to see 500 to a 1000psi depending on the mastercylinder ID.Are you running a booster maybe a aleak there vaccum that is.

DangerZoneRacing
Dirt Maniac

Total posts: 176
posted July 07, 2005 09:21 PM  
Ya I had the original master cylinder on it when this happened last race day so I just replaced it tonight with new...bench bled, and then bled whole system with new fluid. I never checked pressure at the wheels, but boy does the fluid come out at the bleeders, I can get it to shoot across the shop floor quite aways lol. Think theres great pressure there. I dont know a whole heckuva lot about brakes so I'm kinda stumped now.

DangerZoneRacing
Dirt Maniac

Total posts: 176
posted July 07, 2005 09:24 PM  
I did check the booster, i took the master off of it and put a bar across where the rod comes out and pressed on the peddle and it holds and wont go out, There is vacuum there at the booster too. I have a firmer peddle till I start it and it gets vacuum. The funny thing is, is when its running a rev it a little and it feels like the peddle goes down a little more each time I give er gas?

spiirit
Dirt Roller

Total posts: 13
posted July 07, 2005 10:39 PM  
Interesting problem... so when you gas it repeatedly the brakes step down eh? I'd say make sure you got vacuum line in right place on manifold, that line is good, connections are good at both ends and manifold is not cracked, carb. gasket good, bla, blam bla... Engine off, pump brake twice and hold, start engine, pedal should fall a bit, gas it and if it falls more then clean the brake boosters check valve.

DangerZoneRacing
Dirt Maniac

Total posts: 176
posted July 07, 2005 10:56 PM  
Yes it does fall a bit when i start it, then when i gas it it falls even more....surprizing being its already down to the floor lol. Check valve? I run a straight line from back of carb right to booster. Is the check vavle inside the booster or does that go inline? But I know thats not it cuz its been fine since 2003 and just started all of a sudden. I have great vacuum going to the booster. I think its more of the hydalic part of the brakes, maybe? But then again i dont know to much about brakes. Thanks for the input guys.

[This message has been edited by DangerZoneRacing (edited July 07, 2005).]

Bob Berryhill
Dirt Roller

Total posts: 17
posted July 08, 2005 12:18 AM  
Check the adjustment on your rear brakes[assuming they are drum]. They don't have to be very much out of adjustment to cause a low pedal.

DangerZoneRacing
Dirt Maniac

Total posts: 176
posted July 08, 2005 11:42 AM  
Yes I know there out of adjustment cuz the drum is loose. Also someone told me about that valve down on the frame...maybe its bad? what do you guys think? Im headed to my shop in a little bit so I'll check on adjusting those rear brakes. Thanks guys, I appreciate the help to keep my in contention for the points title.

speedwrench
Dirt Roller

Total posts: 16
posted July 08, 2005 08:43 PM  
How about a loose rotor or a stuck caliper piston ?

DangerZoneRacing
Dirt Maniac

Total posts: 176
posted July 08, 2005 08:54 PM  
Yes I checked the rear brakes and there almost completely gone. I adjust them till I get the new shoes. I have brakes again that will stop the car but the peddle is still close to the floor. Do you guys think the peddle will come back up when I put the new shoes in? When I bled the fronts I did check the rotors and there not loose or worn thin either....and when we were pumping the brakes I could see the calipers on both side moving. So I think I pretty much narrowed it down now to the back brakes, They were new at the begining of last year....I didnt think they'd go that fast. But then again we have long straights and tight corners on asphalt so we use alot of brake. So do you guys think new shoes will bring the peddle back to the top then? Thanks. Dan.

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