Break Problem

I have a 1974 C-3 that I have had the brakes worked on twice and shortly after getting it back from the shop the brakes go soft again. I can find no break fluid leakage anywhere. Any suggestions? Thanks ahead of time.
Nick
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Nick Cleghorn wrote:

Look for air getting into the system, or the brake fluid becoming hydrated.
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<DIV><BR>Look for air getting into the system, or the brake fluid becoming hydrated.<BR><BR>-- V</DIV> <DIV><FONT face="Bookman Old Style"></FONT>&nbsp;</DIV> <DIV><FONT face="Bookman Old Style">I am obviously not a mechanic so how does one find out if air is getting into the brake system and where it is getting in?</FONT></DIV> <DIV><FONT face="Bookman Old Style"></FONT>&nbsp;</DIV> <DIV><FONT face="Bookman Old Style">Nick</FONT></DIV></BLOCKQUOTE></BODY></HTML>
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Nick Cleghorn wrote:

Can we assume you are not seeing any wet areas (leaking fluid) on the rotors, lines, or master cylinder?
The most common way air gets in is that one or more rotors are not running true (warped slightly, etc), converting the wheel cylinders into small air pumps as the turning rotor moves the piston in and out rapidly.
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look at the master cylinder cover gasket..could be dry rotted and sucking in air
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Thanks, gentlemen. I will pass these recommendation on to my mechanic.
Nick
<DIV>look at the master cylinder cover gasket..could be dry rotted and<BR>sucking in air</DIV></BLOCKQUOTE></BODY></HTML>
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The typical problem that cause the Corvette brakes to suck air is people turning the rotors unnecessarily or the pistons have corroded from lack of use.
Most brake shops think you HAVE to turn the rotors; you don't. In fact, if you do not have severe wear or grooving,
If someone has removed them and turned them, they can literally pump the pistons in and out going down the road and pump air past the seals into the fluid, so that you have air bubbles. If you crack open a bleeder screw and immediately get fluid with lots of air bubbles, this is probably happening.
The cure is to remove the caliper, bolt the rotors tight, and use a dial indicator to measure the runout.
Then you have to shim the rotor until runout is reduced to something like .005 inches. You will have to check the actual spec as I can't remember off the top of my head. You shim by placing shim stock over the studs between the spindle or hub and the top hat of the rotor.
It is a long and time-consuming process so if they turned your rotors, make them do this without charge and they will never turn another Corvette rotor unless it is absolutely necessary.
If the pistons have corroded in the groove where the seal sits, you can sometimes clean them up enough for them to seal again, but not always. Often you have to replace the pistons. New seals are necessary also.
look at the master cylinder cover gasket..could be dry rotted and sucking in air
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