Brake problem
Thread Starter
Racer
Joined: Feb 1999
Posts: 274
Likes: 0
From: summerfield ( Villages ) FL.
Brake problem
Well Guys I don't get stumped to often but this one has me , started having a soft brake peddle , would come up after pumping it but if I held pressure on the brake peddle it would slowly go down , so I replaced the master cylinder , well after driving it for a block or two brake peddle goes to the floor with minimum brake , pump it and they come right back and don't go to the floor but every time I drive it a bit goes to the floor and I have to pump it to get a good peddle , have speed bleeders on all 4 and have bled all 4 , no signs of leaks and all 4 are working like they should , can not see any bad lines , anyone got any ideas ?
Thread Starter
Racer
Joined: Feb 1999
Posts: 274
Likes: 0
From: summerfield ( Villages ) FL.
Well I found the ABS unit , behind the drivers seat under the floor , don't see a bleeder , what do you do crack the lines ? Looks like 4 lines not sure what is in and out ?
Last edited by Joe; Jun 10, 2009 at 06:52 PM. Reason: add
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
The later years after 92 or so has an ABS bleed on the ABS unit. But I don’t think a 90 has a bleed. It was a non-pressurized line that went from the reservoir of the master to the reservoir of the ABS. You just open the bleed on the ABS and let it gravity feed to bleed while keeping the master full. But I don’t think this is your criteria.
Before installing the new master did you bench bleed it first to get all the air out. This could definitely be a source of the problem.
As far as your actuator rod being adjusted correctly, it is important. If it was misadjusted it wound cause the brakes to drag or a real low pedal but not cause a pedal to sink.
Getting a defective master is a possible but I would bench bleed it again and then bleed all the wheels and see where you end up.
Before installing the new master did you bench bleed it first to get all the air out. This could definitely be a source of the problem.
As far as your actuator rod being adjusted correctly, it is important. If it was misadjusted it wound cause the brakes to drag or a real low pedal but not cause a pedal to sink.
Getting a defective master is a possible but I would bench bleed it again and then bleed all the wheels and see where you end up.
Last edited by pcolt94; Jun 11, 2009 at 11:29 AM.
Thread Starter
Racer
Joined: Feb 1999
Posts: 274
Likes: 0
From: summerfield ( Villages ) FL.
The later years after 92 or so has an ABS bleed on the ABS unit. But I don’t thing a 90 has a bleed. It was a non-pressurized line that went from the reservoir of the master to the reservoir of the ABS. You just open the bleed on the ABS and let it gravity feed to bleed while keeping the master full. But I don’t think this is your criteria.
Before installing the new master did you bench bleed it first to get all the air out. This could definitely be a source of the problem.
As far as your actuator rod being adjusted correctly, it is important. If it was misadjusted it wound cause the brakes to drag or a real low pedal but not cause a pedal to sink.
Getting a defective master is a possible but I would bench bleed it again and then bleed all the wheels and see where you end up.
Before installing the new master did you bench bleed it first to get all the air out. This could definitely be a source of the problem.
As far as your actuator rod being adjusted correctly, it is important. If it was misadjusted it wound cause the brakes to drag or a real low pedal but not cause a pedal to sink.
Getting a defective master is a possible but I would bench bleed it again and then bleed all the wheels and see where you end up.
Well I did bench bleed the MS , and felt like I had gone over board with the wheel cylinders as I change to synthetic brake fluid and wanted to clean out the system , the new MS seems to hold a sold peddle unlike the original , just have a soft to the floor peddle on the first shot then the second time it seems to be where it should , only have the problem on a road test , seems to work the way it should on the lift,
Race Director
Joined: Aug 2000
Posts: 11,470
Likes: 762
- i'm going to follow this one. my 90 doesn't have the best brakes in the world - as compared to my 85. i replaced the MC, and blead the system several times. i originally installed speed bleeders, but went back to the originals - couldn't get a couple of them to stop leaking without excessive tightening. my problem is i have excessive travel, and i feel i have to apply excessive force on the pedal. correct on bleeding the 90's ABS - nothing in the FSM addressing this - the bleeding sequence is RF, RR, LR, and LF (per 90's FSM). my 85 would out accelerate, and stop faster than my 90. i love my 90, but sometimes i wish i had my old 85 back...
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
So lets assume you got all the air out, now what. Here is one off the cuff. Say a piston in a caliper is retracting to much. The piston has to travel to far to contact the pad giving you that extra pedal stroke or something like that. (Just a thought). I would keep pursuing the problem because you don’t want an extra stroke in a panic stop. Maybe a closer check of the break caliper action is in order.
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Thread Starter
Racer
Joined: Feb 1999
Posts: 274
Likes: 0
From: summerfield ( Villages ) FL.
Well when I first bough the 90 it had great brakes , I was always worried about getting rear ended but not that way now , it has been up graded to 96 rotors and calipers !
I have no sign of leaks or fluid loss !
As for performance , 1.6 roller rockers , hooker headers , real side pipes , Hypertech chip,Accel coil, under pullys , tranny shift kit , still stock gears and run in the 12's , I have a new Paxton super charger kit for a 90 or 91 still in the box from 1990 , if I get this brake thing fixed will install the super charger !!
I have no sign of leaks or fluid loss !
As for performance , 1.6 roller rockers , hooker headers , real side pipes , Hypertech chip,Accel coil, under pullys , tranny shift kit , still stock gears and run in the 12's , I have a new Paxton super charger kit for a 90 or 91 still in the box from 1990 , if I get this brake thing fixed will install the super charger !!
Thread Starter
Racer
Joined: Feb 1999
Posts: 274
Likes: 0
From: summerfield ( Villages ) FL.
So lets assume you got all the air out, now what. Here is one off the cuff. Say a piston in a caliper is retracting to much. The piston has to travel to far to contact the pad giving you that extra pedal stroke or something like that. (Just a thought). I would keep pursuing the problem because you don’t want an extra stroke in a panic stop. Maybe a closer check of the break caliper action is in order.
Drifting
Joined: Sep 2003
Posts: 1,363
Likes: 7
From: 1994 LT1 Coupe 6-speed with FX3 & 2000 LS1 Vert 6-Speed with F45 Hunterdon County, NJ
Well I did bench bleed the MS , and felt like I had gone over board with the wheel cylinders as I change to synthetic brake fluid and wanted to clean out the system , the new MS seems to hold a sold peddle unlike the original , just have a soft to the floor peddle on the first shot then the second time it seems to be where it should , only have the problem on a road test , seems to work the way it should on the lift,
It will destroy your ABS and likely swell seals in the caliper.
Because of the ABS unit, only DOT-3 should be used (as some DOT-4's achieve that rating with corrosive additives which can damage older brake systems). Also, whereas some DOT-4 or DOT-3 compatible fluids are ok to use, they need to be replaced more frequently as DOT-4 actually absorbs more moisture over time (than DOT-3), thereby having a lower 'boiling' point than DOT-3 over the same time period (typically 1 yr plus).
Le Mans Master
Joined: May 2006
Posts: 9,226
Likes: 9
From: Irvine Ca
Read this thread...not sure if it covers your year model as I just skimmed the thread out of boredom.....
http://forums.corvetteforum.com/c4-t...n-96-cars.html
http://forums.corvetteforum.com/c4-t...n-96-cars.html
Thread Starter
Racer
Joined: Feb 1999
Posts: 274
Likes: 0
From: summerfield ( Villages ) FL.
When you say "synthetic brake fluid", hopefully you don't mean DOT-5 (silicone)
It will destroy your ABS and likely swell seals in the caliper.
Because of the ABS unit, only DOT-3 should be used (as some DOT-4's achieve that rating with corrosive additives which can damage older brake systems). Also, whereas some DOT-4 or DOT-3 compatible fluids are ok to use, they need to be replaced more frequently as DOT-4 actually absorbs more moisture over time (than DOT-3), thereby having a lower 'boiling' point than DOT-3 over the same time period (typically 1 yr plus).
It will destroy your ABS and likely swell seals in the caliper.
Because of the ABS unit, only DOT-3 should be used (as some DOT-4's achieve that rating with corrosive additives which can damage older brake systems). Also, whereas some DOT-4 or DOT-3 compatible fluids are ok to use, they need to be replaced more frequently as DOT-4 actually absorbs more moisture over time (than DOT-3), thereby having a lower 'boiling' point than DOT-3 over the same time period (typically 1 yr plus).
Thread Starter
Racer
Joined: Feb 1999
Posts: 274
Likes: 0
From: summerfield ( Villages ) FL.
- i'm going to follow this one. my 90 doesn't have the best brakes in the world - as compared to my 85. i replaced the MC, and blead the system several times. i originally installed speed bleeders, but went back to the originals - couldn't get a couple of them to stop leaking without excessive tightening. my problem is i have excessive travel, and i feel i have to apply excessive force on the pedal. correct on bleeding the 90's ABS - nothing in the FSM addressing this - the bleeding sequence is RF, RR, LR, and LF (per 90's FSM). my 85 would out accelerate, and stop faster than my 90. i love my 90, but sometimes i wish i had my old 85 back...Well your the MAN , a big THANK YOU ! I bled them the first time old school furthest to closest , tried it your way , bleeding sequence RF, RR, LR, and LF and they work like they should , I don't get why but dam who cares if it works , O I was alone today and the speed bleeders seem to work fine Thanks again
