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Author Topic:   NEED HELP ON MASTER CYL/ BRAKE PROBLEM
bobaluuu
Member
posted February 27, 2004 08:15 PM
We bought a car with the rear 7.5 changed over to disc using a speedway kit.
the pedal goes to the floor on the 1st hit and pumps up firm on the third. Even then stopping power is inadequate. The car has two wilwood proportioning valves added in to the mix. I noticed the rear calipers are not exactly parallel(about 1/16 inch) to the rotors and straighten up on the first pump and engage on the second.
we have bled a gallon thru with pwr bleeders and cracked every joint and bled there too
We added a disc/disc m/c, a 10 lb residual valve and a 1/4 line to the rear. still needs pumping and gushes back into the rear bowl when pedal is released, I'm going for the caliper alignment as a base problem. Will post back when fixed, thanks and still offer suggestions.

[This message has been edited by bobaluuu (edited March 05, 2004).]

joetaylor
Member
posted February 27, 2004 08:27 PM
I USED A MASTER FROM A 2000 CHEVY TRUCK W/ REAR DISK WORKS GOOD

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U LIFT U LOOSE


crew42tx
Member
posted February 28, 2004 05:02 PM
I would get a m/c for a early 70's vette with manual brakes and definately fix the alighnment of the rear calipers to the discs. jmo


Okie11m
Member
posted February 28, 2004 09:29 PM
Early 90s Chevy van with disk brakes works good too.


JRB13
Member
posted February 29, 2004 09:14 AM
the only problem I have seen or heard of when using the later model stuff is that it is usualy for power brakes and tends to have a real hard pedal and when excessive force is used to apply the brakes becouse of the hard pedal the the brakes lock up instead of just slowing you down.

JUST MY OPINION AND EXPERIENCE

te33
Member
posted February 29, 2004 05:49 PM
33 is right on the residual valve use the blue 2# one it will work good and keeps the fluid from returning....After the car sets awhile look and see how much space there is between the piston side (brake pad)and the rotor... depends on how they fit everything when installed if the pad backs away from the rotor enough you can install a wore down brake pad to take up the space that will give you alot more brake pedal on the first stroke.....let me know what you find out......Towman


bobaluuu
Member
posted March 01, 2004 09:22 PM
79 vette master cyl and a 2 lb residual vavle
cured it, thanks guys, for a disc/disc master cyl it was only 18.00 rebuilt all the later model alum units were 80 to 120 each. I know it cost me 2 lbs but we have 53.7 rear % anyway.

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Light it up, Baby!


doug
Member
posted March 02, 2004 07:42 PM
is this problem in the shop on stands or at the track when you go out, thanks the buzzard7


bobaluuu
Member
posted March 05, 2004 08:58 PM
[QUOTE]Originally posted by bobaluuu:
UPDATE: Brakes not fixed. Another hiney in the seat told me it was, but it aint. There is no visible distance between the rear pads and the rotors(with wheel bolted on). The pedal still takes two or three strokes to pump up even when we put a 10 lb residual valve on and changing to a 1/4 inch line. We noticed something:in the m.cyl with the cover off when you release the pedal after the 3rd pump there is a small fountain of fluid about 2 inches tall gushing back into the bowl. I believe there is an alignment issue that needs addressing in the calipers. more to follow, hopefully good .


crew42tx
Member
posted March 06, 2004 06:54 PM
the first thing that you should have adressed was the caliper alighnment.


bobaluuu
Member
posted March 07, 2004 07:20 PM
[Did that today, didnt help. Calipers off brackets with steel bungs between caliperand piston still getting fountain of fluid. Now suspect swelling in rubber lines, theres three back there. Will **** that tomorrow..


6pack
Member
posted March 08, 2004 03:05 PM
Had a similiar problem on my 68 camaro(street car)after puting a ford 9" rear end with disc brakes. Tried changing master cylinder, residual valve and lots of pumping the pedal and fluid, nothing worked. I jacked front end up and took rear tires off and set the rear down low, opened up bleeders in rear and let alot of fluid come out on its own (no pumping the pedal) just gravity. For some reason I couldn't work the air out of the line by conventional bleeding. This got the air out and cured the pedal and stoping power. Brakes work great know, Stop that 110 mph 1/4 mile ride quick.


tfiracing
Member
posted March 08, 2004 10:36 PM
bleeders are straight up. still going thru some pump up problems but getting closer.
put a 1/8 th plate on the pad and got more
pedal(less volume to move). gonna try reverse injection of fluid to push air out if any there. You guys are great. we now have enuf to squat the rearend on one pump,
doing a parkin lot drive.


bobaluuu
Member
posted March 11, 2004 09:25 PM
Oh yeah, also put on new rear hoses to calipers.


driver27
Member
posted March 12, 2004 09:28 AM
found another contributor to the problem.
Looking closely found the pads were riding
on the lip where the rotors widened to the hat. Cut the pads to clear the lip and got some more pedal(could have been similar to a caliper in bind). track testing sunday, we'll see then.


bobaluuu
Member
posted March 30, 2004 08:49 PM
update, problem fixed by trimming pads off lip of rotor. patience , persistence, and plain good luck. thanks to all. We lapped the field except two cars on our first outing.

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Light it up, Baby!

[This message has been edited by bobaluuu (edited March 30, 2004).]

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