# 88 Chev C30 brake trouble



## jr in va (Apr 15, 2015)

Having problems with my ton truck's brakes.Oe half pedal and no stopping unless I pump the pedal.Poor braking then.I am wondering about the vaccum boost.Thanks


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## Thorim (Jan 19, 2015)

Master cylinder might be going bad.....


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## glasswrongsize (Sep 15, 2015)

Check fluid first, if it IS or WAS low/out in one chamber or the other, you probably have air in the lines and the brakes will need bled. If not, it doesn't take long and is easy to bleed them to make certain that there is no air in the lines.

If no air in lines, my next suspicion would be the back brakes are not adjusted properly. There is a star wheel adjuster in the back brakes and they can rust up and quit adjusting. The back brakes are returned with a spring whereas the front calipers just relieve pressure and don't reset to "open". That being said, if there is too much gap in the back brakes, pumping will help because you can pump the pedal fast enough that it catches the rear brakes before they are totally reset ratcheting them a little tighter than the previous pump. once the brakes are released for any appreciable amount of time, they return home and you need to pump again to get pedal.

If out of adjustment, the automatic adjusters cannot work; ie they can only maintain adjustment and will not adjust out-of-adjustment brakes. An adjustment tool is available, but a flat screwdriver is sufficient.

Side note: the hind brake adjusters only adjust when brakes are applied while backing.

Some (if not all?) mid 80s Chevy trucks had a valve over the rear axle; it has a linkage that attaches to the underside of the bed. When the bed is lowed, the truck knows that more weight is in it and it opens the valve further thereby allowing more flow to the hind brakes to compensate for the need to stop more weight. I doubt this to be the issue, but thought it worth mentioning. If the valve is bad/linkage comes off, you still have good brake pedal but not enough pressure makes it to the brake cylinders. Come to think of it, pumping would not help, but I will leave this portion remain in the event that it helps another's problem.

73, Mark


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