help brakes acting up

88 XJ, 4.0 6cyl auto trans.

I was checking my suspension and i noticed that my caps for my axel u-joint on the drivers side was not all the way pressed in and by it being out like that apparently it scraped up metal from the calipers bolts and one of the bolt holes. But i dont think it really effected anything

anyway i had to take off the caliper and when i put the c-clamp on i forgot to monitor the master cylinder to make sure it didnt overflow and it did, my question is with the little amount that came out is that enough to mess with brake performance?

because after i put everything back together and drain the diff and change the gasket i went to do a little test drive and the brakes felt weak, felt independable scared to drive it around the block type of scary,

can anyone help any ideas? what should i check? The master cylinder is not to the rim, is it suppose to be?

I just did my wifes rear brakes on her tj rubicon (disks). The brakes felt a little spongy at first, I think because the caliper piston was to work its way down to the rotor. Did you try pumping the brakes for a few minutes with the engine running?

What sometimes happens when compressing the caliper is that crud in the lines is pushed back into the MC, and the piston seals are effected.

Try bleeding the system. There are numerous threads on here, some like vacuum, some like the buddy system, some like the gravity method. Do a search and you will find plenty of opinions, in my experience they all work.

Master cylinder brake fluid does not need to be to the rim. As long as no air gets into the bottom opening, you are OK for that. After you push the piston in, it needs to seat everything back down again. Pump it hard while stopped or barely rolling. If pedal holds up and doesn't slowly go to the floor, bleeding is the next step. If you never replaced the brake fluid, its a good time to do that. It goes bad in a couple of years.

how do i do that
do i suck the fluid out the cylinder and add new, or is there more to it?

Bleeding brakes: The best way is the GRAVITY method. 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 futhest 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. 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.
4.) Pass front.
5.) Drivers front. Etc.

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

is there a special position to get to the bleeders i need to know about cause i was just gonna jack the thing up

and what rubber pieces are you referring to?

You don't need to jack up an XJ. They have enough clearance to crawl under. THe rubber cups inside the master cylinder.

k thanks