I have a 1994 GMC Serra i had a brake line that started to leak for the back brakes so i replaced the whole line from the front to the back and i went to bleed the brakes for the back i had a helper pump...
If you have replaced the line from the front to the back, there is a lot of air in the line. The proper way to bleed the brakes (for the average guy with no shop) is to;
#1, OPEN the bleeder screw,
#2 THEN have your friend push the brake pedal down fully to the floor and HOLD IT DOWN. Then you
#3 CLOSE the bleeder, so no air can enter the line from there,
#4 THEN have your friend let the pedal up after you have closed the bleeder screw.
Repeat this process untill you have fluid coming out of the bleeder screw. Remember, after your friend has pumped the brakes a few times, the fluid level in the Master Cylinder's reservior will
go down, and you need to refill it as the fluid gets pumped into the line. Do not let it go empty, or you will have to start all over again. Every time the brakes get pumped, the fluid will only go down the line a few inches, so you will have to do this Procedure many times, like 15 or so.
Once you get the fluid coming out of the bleeder screw, do the bleed procedure a couple more times, until there IS NO AIR left in the system and all that is coming out is fluid with NO bubbles.
You MUST do BOTH sides, right AND left of the rear, as there is only a single line to the rear, which splits into two above the axle, and now there will be air in both sides. Then, tighten the screw, top off the master cylinder, and you are done.
If you simply opened up the bleeder screw, and then pumped the brakes with it open the whole time, the master cylinder simply pulled air back into itself every time you let the brake pedal up, resulting in no fluid being pumped into the line.
Also, if the master cylinder ever was EMPTY, then you may have to bleed the cylinder itself. This is done by disconnecting the brake line (rear brake, the one you just had off) from the cylinder, and putting a hose from the line inlet in a small loop back into the master cylinder's reservior. Then, pump the brakes. The cylinder will then pump the fluid directly back into itself. The idea is that you do not let the master cylinder pull any air back into itself, from the line inlet. So, as the cylinder pumps out the air, the only thing it can get back in is FLUID. Do this until there are no more bubbles coming out of the line.
Then perform the above-mentioned Bleeding Procedure. If you do the Bleeding Procedure correctly, and the fluid level in the master cylinder does NOT go down, and you are still not getting fluid to the bleeder screw, then that will tell you that you have to bleed the Master Cylinder.
Good Luck To You.
Jun 21, 2011 |
1994 GMC Sierra