Is this signs of a bad master cylinder?

[ShadowRejects]

Even money on it being air after changing the master....

i mean I bled it properly... i think i need to bleed the brakes again.

 

[magimerlin]

Did you bleed the master before you put it on the truck??? If the brake light comes on it usually means you had a leak some where and the check ball in the combination valve moved. Look on the end of the combination valve, is there a little push pin looking thing coming out of it?? If so you will have to push it back in and bleed the brakes again. When you first changed the master where either the front or rear sections of the master empty of fluid??


Sent from what use to be a great country.

 

[DGA1]

Bench bleeding the MC will save you a lot of headache. Did the new one come with a bleeding kit (couple of clear tubes, plastic fittings with nipples on them that thread into brake line ports, and couple of little hold down clips)? Get them if you don't have them and pump that MC piston with a screw driver till there is nothing but clear fluid circulating from the ports back to the fluid reservoir. You'll still have to bleed all 4 lines after you put the MC back on, but if you bench bleed the out of the MC you'll know that there is no trapped air in it.