Brake issue

[Dano93]

When hard braking my pedal drops down and all brake power goes the the rear wheels what causes this issue new master and lines and wheel cylinders and calipers on a 1987 k20 with rv package

 

[SquareRoot]

............

 

[1985c20]

Rebuilt master cylinder or new? To me it sounds like a bad master cylinder. Many of the rebuilt ones are worse then what you take off

 

[idahovette]

For the price I never get a reman brake or wheel cylinder, and never a reman H2O pump.

 

[C10MixMaster]

i have to lean towards a bad master cylinder. you did say you replaced lines are you sure the front and back are not switched.

 

[dvdswan]

So what give the idea that all power goes to the rear brakes? Do they lock up? Have you looked at the rear brakes to see if you have an axle seal leaking? Are the front brake hoses old and worn and need replacing? Does the brake pedal actually sink after brakes are applied?

 

[highdesertrange]

yeah we need more info. it does sound like the master. are you sure you got all the air out?

 

[Dave 84]

Have a partner pump the brakes and hold then crack the line right at the master cylinder see if it has normal pressure if it has none your master is bad if it is strong pressure most likely it's another issue che all rubber lines as they can swell even if there new just check. Very specific details will help pin point much better!