97+ Brake Question

I let my brake fluid get far too low and my brakes became very sloppy.
Filled the tank back up and the brakes are still mushy and now the brake light on the instrument cluster won't go off.

I assume I sucked in some air and that is why they are sloppy, but is there some sort of sensor that makes the light come on when brake pressure is down.

Starting my lift this afternoon, and I'm gonna have to do some brake work anyway, I'm just making sure its nothing major.

thanks
T

Not sure if there is a sensor but you're definitely going to have to bleed the system. Since air got into the master cylinder, you're going to have to pull it and bench bleed it. The procedure is described in Haynes or Chilton's book. I'm curious how it got so low in the first place. Go over all your brake lines/connections to make sure there are no leaks.

I can't just bleed the lines??

I've got to pull the master??

It probably got low because I haven't checked it in two years

footdale said:

Not sure if there is a sensor but you're definitely going to have to bleed the system. Since air got into the master cylinder, you're going to have to pull it and bench bleed it.

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I'd suggest buying a big bottle of brake fluid and bleeding all the brakes on the jeep first. Start with the farthst corner and go through a bit of fluid before you move up to the rest.

Kejtar said:

I'd suggest buying a big bottle of brake fluid and bleeding all the brakes on the jeep first. Start with the farthst corner and go through a bit of fluid before you move up to the rest.

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I agree. You'll probably go through two refills just on this corner and maybe a half to a full refill each on the driver's rear and front left and right.

There is a switch built into the proportioning valve that triggers the light on the dash. This switch is activated any time the is a pressure imbalance between the front and rear brake circuits.

Since you ran one side of the brake system down, the pressure dropped in one side relative to the other, triggering the light. The switch should reset once you restore the pressure balance.

That said, it's HIGHLY unusual to run one side of a brake system low on fluid unless something developed a leak. The reservoir for the brake system, (located on the Master Cylinder), when filled properly with fluid, has enough volume to allow the brake linings to wear down all the way and still not allow the system to "run out" of brake fluid.

Something has caused your reservoir to run low to begin with, and that, coupled with the wearing of your brake linings, has caused this entry of air into the brake system.

So.......the question of the day is: where is the leak?

Before you go bleeding your brake system, and restoring the brake function you should go looking for the leak. Otherwise, what will happen is you will fix the problem for a little while, and then once all the new fluid has leaked out, you will back to where you are now.

Just my thoughts...............