bad master cylinder symptoms

[//<86TA>\\]

so, ive been trying to figure out my pathetic brakes, i have about 1-1.5" of travel in the pedal, then the pedal stops dead, the harder you push, the more the firewall bends. The brakes suck, cant even lock a wheel in gravel, and this is with c5 vette brakes. I took the master, and prop off, gutted the prop, plumbed in an adjustable rear prop valve, blead everything and i still have the same issue. If i disconnect the master from the booster, i can push the pedal to the floor. If i bolt the master to the booster, even without the brake lines attached to anything, the pedals only goes an inch or so and gets hard. Im thinking the master is shot? agreements? thanks -Phil

[RazorN8]

When my master went bad, the pedal still felt fine it just wouldnt put any pressure on the front calipers. I found out when doing a brake job and trying to bleed the front brakes there was very little fluid coming from the bleeder screw. Usually the seals inside the master cylinder go bad and you therefore lose pressure. When installing a new master cylinder you push the piston into the master cylinder while bench bleeding the cylinder. You could try taking the master cylinder off the car and pushing the piston in to see if there is an obstruction in the cylinder. Just be careful not to go to far or too fast or you may damage the internal seals.

[l_dis_travlr]

So you got the prop valve plumbed in. Pic's?

I would bet the m-cyl is probably the culprit.
RazorN8's bench test does sound like a good idea.

At the risk of seeming really pi..y, did you possibly
try servicing it, & re-assemble the plungers wrong?

At any rate, I think rebuilt ones are relatively inexpensive --
at least compared to the corvette upgrades in place.

Good luck, & keep us posted.
(I still want to know where you got the bubble flare T.)

[skirkland1980]

sounds like the master cylinder doesn't have enough volume. what all do you have on the car (for brakes)?

[//<86TA>\\]

Originally Posted by skirkland1980

sounds like the master cylinder doesn't have enough volume. what all do you have on the car (for brakes)?

no issue with volume.

c5 vette fronts, 4th gen pbr's for the rear, LS1 4th gen master cylinder, and something was wrong with it, it had a weird leak. I put a new one on and things are better, but still have some air in the system. I should have the adjustable prop re-plumbed this coming weekend and have the factory prop completely removed. then i will have some pics.