I'm at a loss here. I have a 99 Cherokee 4 door sport. On Friday I had good brakes, Saturday morning my brake pedal hit the floor. Got to looking for a wet spot found nothing, master is still full. I do see fluid in the master move when I had my son press the brake pedal. Any help?

 

How much fluid is in the master? You really should not see movement.

 

Hi BlueRidgeMark, The master is full. Now when I say I see movement, I use a marker on the master, and I look at the mark as the pedal is pushed and released. I know what your saying I shouldn't really see movement. There has to be something stupid I'm overlooking.

 

Nah. Could be as simple as a failed MC. You could roll the dice and replace it.

OR, maybe it's possible to test it by removing the brake lines and plugging the ports. I dunno what thread size you'd need, I'm just brainstorming here. If you could plug the output lines, then the brake pedal should feel really hard. Almost no give to it at all. But if the seals in the MC have failed, you should be able to depress the brake pedal with little resistance. Might be worth a try if you can find threaded plugs to fit.

I've never heard of anyone doing this; I'm just thinking out loud here. Conceptually, I think this test should work. Maybe someone has a better way....

 

I'll give that s try, as I said something simple in just overlooking. I'll let you know how it goes.

 

don't suppose brake pedal came unhooked under the dash.