need some input - brake issue (still)
Thread Starter
Race Director
Joined: Aug 2000
Posts: 11,470
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need some input - brake issue (still)
i've posted this several months ago, but this time i have some updates. when i got my 90, i felt the thing didn't stop near as good as my 85. since then, i've installed stainless (flex) lines, and a new (delco) master cylinder. i also installed a set of russel speed bleeders, but i'm not as happy with this set as well as the ones i installed on my 85. seems i have to tighten them up quite a bit to get them to stop leaking. i just may go back to the stock bleed screws. anyway, i've blead the thing three times, but the pedal still feels a bit spongey, and when applying the brakes, the pedal drops down about 3/4 of the travel to the floor - that seems excessive to me. tomorrow, the stock bleed screws go in, and i'm going thru the two-man brake bleeding thing. still think i dont have all the air out of the system. until then, any comments - ???
BTW, i did a bench bleed the master cylinder.
BTW, i did a bench bleed the master cylinder.
Le Mans Master
Joined: Mar 2001
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From: Life is just one big track event. Everything before and after is prep and warm-up and cool-down laps
Cruise-In III Veteran
Cruise-In IV Veteran
St. Jude Donor '12
If the two man doesn't work,only thing I can think of is some air got in the ABS.
Thread Starter
Race Director
Joined: Aug 2000
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is there anything special about bleeding brakes with ABS?
thanks - good point. is there anything special about bleeding brakes with ABS? my 90 FSM doesn't indicate anything other than a conventional, single-sequential, bleeding of each caliper. i'm going to give this one more bleeding, then maybe i'll go down to my local dealer for a pressure bleed...
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
If the pedal drops down to far the actuator rod on the booster might need to be adjusted. There might be to much clearance. There should be about 1/16 to 1/8 inch clearance before the rod contacts the master. To little clearance and the brakes will drag when things heat up.
Trial and error is the basic method. Jack one front wheel up (to spin it) to see if you have gone to far and get a feel where to stop adjusting or back off. You have to hold the shaft of the rod and adjust the end nut in or out. Don’t remove master, just take off mounting nuts and pull back 2-3 inches.
You have a interesting comment about the speed bleeders. I have 2 sets and never could get the things to seal properly. I only use them to bleed the brakes when I have to do work on it and they are great for that. But when I’m finished I put the standard bleeder back in also. Not a big deal, don’t have to perform any extensive work to often now that I have things working well.
Trial and error is the basic method. Jack one front wheel up (to spin it) to see if you have gone to far and get a feel where to stop adjusting or back off. You have to hold the shaft of the rod and adjust the end nut in or out. Don’t remove master, just take off mounting nuts and pull back 2-3 inches.
You have a interesting comment about the speed bleeders. I have 2 sets and never could get the things to seal properly. I only use them to bleed the brakes when I have to do work on it and they are great for that. But when I’m finished I put the standard bleeder back in also. Not a big deal, don’t have to perform any extensive work to often now that I have things working well.
Thread Starter
Race Director
Joined: Aug 2000
Posts: 11,470
Likes: 763
If the pedal drops down to far the actuator rod on the booster might need to be adjusted. There might be to much clearance. There should be about 1/16 to 1/8 inch clearance before the rod contacts the master. To little clearance and the brakes will drag when things heat up.
Trial and error is the basic method. Jack one front wheel up (to spin it) to see if you have gone to far and get a feel where to stop adjusting or back off. You have to hold the shaft of the rod and adjust the end nut in or out. Don’t remove master, just take off mounting nuts and pull back 2-3 inches.
You have a interesting comment about the speed bleeders. I have 2 sets and never could get the things to seal properly. I only use them to bleed the brakes when I have to do work on it and they are great for that. But when I’m finished I put the standard bleeder back in also. Not a big deal, don’t have to perform any extensive work to often now that I have things working well.
Trial and error is the basic method. Jack one front wheel up (to spin it) to see if you have gone to far and get a feel where to stop adjusting or back off. You have to hold the shaft of the rod and adjust the end nut in or out. Don’t remove master, just take off mounting nuts and pull back 2-3 inches.
You have a interesting comment about the speed bleeders. I have 2 sets and never could get the things to seal properly. I only use them to bleed the brakes when I have to do work on it and they are great for that. But when I’m finished I put the standard bleeder back in also. Not a big deal, don’t have to perform any extensive work to often now that I have things working well.
Safety Car
Joined: Oct 2008
Posts: 4,689
Likes: 4
From: Yucaipa CA
there was a thread few days back about the abs thing behind the seat not doing a pretest and that causes the problem but not sure if it applied to earlier years.
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Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
FYI - I have read on the Forum that the earlier C4s (85s) with the single cylinder caliper stopped better the later ones as you described.
Last edited by pcolt94; May 26, 2009 at 10:08 AM.
Thread Starter
Race Director
Joined: Aug 2000
Posts: 11,470
Likes: 763
thanks all - i re-installed the stock bleeders, and blead the system for the forth time. the 90 stops a lot better now, and the pedal travel is about half way to the floor. not where i'd like it, but acceptable. i'm starting to think the speed bleeders might have been the problem - i don't know - ??? anyway, i went out for a test drive, and stood on the brakes, and it felt like the ABS actually kicked in. i may try a slight adjustment on the booster actuator rod down the road. the 90's brakes are a lot better, but i still feel like my 85 stopped a whole lot better. i might try some better pads. the ones i have, although new, are autozone cheapies. any recommendations on performance pads...
