brake bleeding issues

ok its a 1990 comanche with 4 wheel disc (ford 8.8) we put all the new lines for extending them and everything and bled them until all the air came out.. still once the truck turns on the pedal goes to the floor. i dont see any leaks am i supposed to bleed the master cylinder too? im kind of lost.. brakes arent my thing


thanks,
phil

If your master is new, yes. It needs to be bench-bled before installation.

If you had the calipers off, or put on new calipers...check to see if you put them in right. If you put the right side on the left and vice-versa your bleeders are in the wrong position. They should be at the TOP of the caliper. Ask me how I know...no wait, don't.

If none of the above is true...keep pumping.

Start with rear right, then rear left, front right, front left. Furthest away from Master working towards closest.

Or else don't pump.

Bleeding brakes: The best way is the GRAVITY method. The only problem is it takes a lot of beer and you don't want to drive right after. (CAUTION: YOU MUST BE 21 TO BLEED YOUR BRAKES THIS WAY!) I use it whenever I replace brake cylinders or calipers, but mostly it's just to change the brake fluid, which I do whenever I change shoes or pads. Ideally you change brake fluid at least every other year. If you worked on old cars and saw rusty pistons, you'd know why, but people also say that old brake fluid boils and won't stop you right.

1.) Get the car in a position where you can open up the bleeders. I always like to break them loose with a 6 point socket being careful not to break them off. If you can, spray them with breakaway or similar a day before.)
2) Starting with the bleeder furthest away from the master (pass. rear), open it about 1 turn. You can put a little hose and cup on it if you want to keep the old fluid from running all over. Make SURE to keep the master cylinder topped off with fluid and DON'T let it get down to where air gets back into the master cyl. Let it flow this way until the fluid comes out of the bleeder clean. This will take at least 2 cups or so of brake fluid. Using gravity alone, you can drink 2 beers while topping off the master cylinder for the first corner. (CAUTION: Do not store brake fluid in beer cans or put beer into master cylinder. Drinking a little brake fluid however will probably not kill you. Beer in your brake lines might.) Snug up bleeder good when you're done.
3.) Proceed to drivers rear and repeat. It won't take as long because the long brake line has already been purged of the old fluid. So you have to drink your beer faster.
4.) Pass front. Drink even faster.
5.) Drivers front. Etc.

Patience can be substituted for beers, but that's no fun. :cheers:

This prevents the rubber pieces from going any further than they are used to and self destructing.

master cylinder is stock... worked fine before we lifted it and put the 8.8 in.. so should i bleed that too? and if so where

(a) make sure the brake bleeders are at the tops on both rears since you just installed it, might have accidentally swapped the calipers.
(b) the brake bleed procedure on the MJ, with stock braking system (did you eliminate the rear height sensing valve?) is special! You bleed all 4 in the normal order, then open a front bleeder and slam on the brakes to shuttle the bypass valve in the proportioning block, then bleed both rears again (right, then left) with the front still open, then bleed all four again normally. This is because the MJ braking system has two lines to the rear brakes, one is a bypass line and the other is used normally. If you don't get all the air out of that line by enabling the bypass temporarily you can/will have a soft pedal.

Try bleeding the master cylinder with it held so that the fittings on the side point up at about a 45 degree angle, I find this helps persuade the air bubbles to move into the lines faster than normal. Also, you might look into a WJ or 95/96 XJ booster+MC - they will increase your braking ability greatly.