brake problems

ok my problem is that yesterday i was out playing on an icy county road wipping donuts and such. i went to stop afterwards and my brake pedal went right to the floor, so i pumped it a few times and good as new. then i went on my way and whipped around again by accident. i lost my brakes again. i then went playing around a bit more to try to see if it would do it again but it wouldnt. now tonight it is doing it alot more and my pedal always goes just about to the floor. then just before i got home it started making a grinding sound that i think was coming from the front when i put on my brakes. my fluid is topped up by the way. any ideas what to check?

Check for wheel bearing damage, jack it up...hands at 12 and 6, try to move tire....if it moves, see where the movement is coming from...if it is not moving at the ball joints you may have ate a hub...that can cause enough movment to affect the brakes. if everthing is tight...pull both front wheels and check pads.

DO THIS ALL NOW! Do not drive it again unitl you have this fixed....promise?


Rev

Rev Den said:

DO THIS ALL NOW! Do not drive it again unitl you have this fixed....promise?


Rev

Click to expand...

Thank you rev, just going to the store tonight, i saw two wrecks, each involving rearending cars. Its scary to take my 2 month old baby out with all the crasy people in the world.

Oh, and if it is not any of those things, check your master cylinder, it should have not just gone out whammy style, but it can be full, and not leak, but not be able to hold or get pressure. Also check your brake lines, make sure you have not damaged one to the point when you push in on the brakes it is not balloning out rather than transfering fluid.

i will check it all tommorow. also my front hubs and brake pads are both only a couple months old(not saying they cant be damaged just hoping not) also what is a good way if there are any to test the master cylinder
thanks::

Wouldn't hurt to also bleed the brakes just to eliminate the theory that there might be some air in the lines. Start at back right and go around with the farthest wheel from master cylinder.

Most common cause of air in the system (in my experiance) is a leaky rear wheel cylinder (fluid out, air in). The pedal goes way down, the brake light comes on. Gently pull the rubber cap off of the ends of the rear brake cylinders and see if fluid comes out. Bleed the brakes.
I've had small stones or gravel jam between the pads and disc before.
A couple of times over the years, I've seen a flacky master cylinder, just up and fail for a few seconds (though never in an XJ dual system master cylinder, in the older single piston type not used anymore). Then fail again after a few weeks.
If it fails once and you don't die, it's a message from God to get it fixed quick.

it almost seems like there is air getting in the line because the pedal will completely go for a sec then i just pump it up and it is fine again although it isnt getting very hard anymore. also it doesnt seem to be losing brake fluid at all because the master cylinder didnt go down any

when you bleed your brakes also check your rubber brake lines. its said that sometimes the rubber degrades and can allow the line to bulge when the brakes are applyed. also check for a minute leak.

Try this: Start the engine, and push down slowly but firmly on the pedal and hold it there. Does the pedal hold, or does it sink? If it sinks, check carefully for leaks anywhere. If it sinks without any external leaks, it's the master cylinder. Many times a bad master cylinder will let go intermittently, but still work when you pump it or hit it hard. The rubber cups on the pistons expand under pressure. When they wear out, it takes more pressure to expand them enough to seal. They will often catch well enough to work, especially when you hit the brakes hard and fast, but may fail to make a good seal when you brake more slowly.

ok then it sounds like the master cylinder i think. i will try that agian today. dam always when you are getting ready to go on a 4x4 trip