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Old 01-26-2013, 09:18 AM
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Quote:
Originally Posted by radconjon View Post
First of all, thanks to anyone who takes the time to sort through this.
I have tried to be thorough in trouble shooting this system.
I am trying to get a good brake pedal and am not having a lot of luck. I have scoured this and other forums as well as vendor web sites. I think I have tried pretty much everything but I am at a loss.


I have:
51 Chevy Sedan Delivery
Mid sized GM calipers up front
Cadillac Calipers w/ ebrake integral adjusters out back
1 1/8" Corvette master cylinder with a 7" dual diaphragm booster on the firewall. Supposed to be a disc/disc MC. Pedal ratio is about 5:1
The front brakes are a SSBC kit and the rears and MC are from MBM.
The reservoir closest to the MC is plumbed to the rear. All the bleeding was
done slowly, with the vacuum pump running so I get the full action of the booster

So far I have:
Carefully bench bled the MC
Checked clearance between booster pin and MC cylinder.
Adjusted rear ebrakes - calipers are snug on rotors at this point.
Mounted MC and blocked both front and rear ports - hard pedal
attached front brakes (rears blocked) and bled - good pedal
attach rear brakes and bled - crappy pedal
block drivers side at wheel, bled other side - OK pedal
block pass side at wheel and bled other side - OK pedal
hook it all up and bleed - crappy pedal.
Bled with rear calipers off and indexed so bleeders are up as
perfect as I can get them.

I have tried swapping front and rear brake lines at the MC but did
not seem to make a big difference. I replumbed it to the original setup.
Bought stock in the companies that make brake fluid.

I am leaning towards having a volume problem but that does not ring true since I already have a 1 1/8" bore MC. Any GM brake engineers out there?
Suggestions?
Thanks
Jon
Just to be sure, are you reinstalling the rear calipers after bleeding and before your "pedal check"? I chased a problem on mine that involved using hardwood blocks as substitutes for the rotors while bleeding AND doing a pedal check. The blocks were compressing enough to falsify the pedal check and only after reinstalling the calipers did I get a good pedal.

Russ
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