GM-GMC: brake light, proportioning valve, bleeders

Question
I recently had a to replace a brake line that had a hole in it.  The line that goes to the rear.  I replaced the line and bled the system, but the brake light is still illuminated.  

Answer
Chris,  

  I have had this happen many times and its never a fun thing! Basicly the Proportioning Valve has a sensor in it that slided iside the valve and blocks-off either the front or rear sytem when it has a failure like your broken line. This is to keep the remaining sytem operating. As it slides it opens a switch on top of the valve and turns on your light. Now....There is a couple of ways to try to get it out......One way: simply turn the key on so your Brake light come on and stomp on the brake pedal hard and take your foot of right away....kinda like if you were stomping on a bug! I know its not very tecnical but some times this is enough to Move the valve back to its original position. If you are lucky this worked! This has actually only worked a few times for me. Another way: You will require a helper for this.....Go to one of the front bleeders and open it as your helper pushes down on the brake pedal, as the pressure leaves the front sytem the valve will want to slide toward blocking off the frt....so make sure your helper is watching the light as he pushes on the pedal, as soon as the light goes out he must tell you and you need to close that front bleeder....this must happen fast! You may need to try this a couple of times.....Also, if you manage to get the light to go out his way but as soons as you pump the pedal a couple of times it comes back on, try bleeding the rears again you probably still have some air in there somewhere. Make sure you check your fluid lever often while bleeding you'll make thing much worse if you run that master cylinder dry! Good Luck!