brake light on after replacing mc..

[78 K-10]

jeez i feel like im bothering everyone with tedious stuff. oh well.. so i just replaced my master cylinder, put new pads on the front and bled the system. i finished and started up the truck. the brake light came on (red) on the dash. never seen this light on b4... sumthin not right or maybe theres a buttom to push after installin new mc?

 

[crazy4offroad]

Still air in the system, you have air in the proportion valve. Keep bleeding it!

 

[78 K-10]

ok.. thanks man

 

[78 K-10]

where is the proportioning valve?

 

[crazy4offroad]

On the crossmember under the radiator. It can be a real BITCH to get all the air out of it.

 

[78 K-10]

ok.. ima run down to the shop to look for it
so the front brakes bled just fine. still random air bubbles in rear. just bleed and bleed and bleed is all i can do?

 

[crazy4offroad]

HotrodPC advised me that the check ball in the proportion valve can get air behind it or gets stuck, and sometimes to get it out you have to have your pedal-pumper push really hard, and bleed the rear out fast and hard, and till the pedal hits the floor. It took a lot of bleeding but I finally got mine lined out. While you're under it look along where the line goes to the back and see if you find any spots that might be leaking along the way. I've replaced every hard line on my truck when I first got it, got tired of fixing one pinhole and then another pop up.

 

[towman]

sometimes you can tap on the valve to help work the air out also, lightly not with a sledge hammer

 

[78 K-10]

when we're bleeding the rears the pedal will only go down like half of the travel that the front does, is that normal?
is there a reset button on the proportioning valve? does gravity bleeding work on rear brakes on our kinds of trucks?

 

[towman]

yes gravity bleeding does work