Changed master cylinder, "Brake Light" stays on.

[snblinn]

I have a 2001 XLT w/ 5.4, ABS and all wheel drive.

Last week I was slowing for a stop and noticed my pedal went farther than usual, not to the floor though.

This got progressively worse. If I pressed and kept steady pressure on the peddle, the truck would stop fine. But if I pressed hard and released (as if stopping too soon and releasing the peddle slightly to coast) the peddle would go all the way to the floor.

I replaced the master cylinder with an Autozone unit. I bench bled it, installed and bled all four corners starting with the farthest first.

Now the brakes seem to work fine but the "Brake Light" is illuminated on the dash.

Emergency brake is off.

Any ideas? Thanks, Steve.

 

[Trainmaster]

I guessing here: The system has a "differential or proportioning valve" somewhere that lights the brake light when one side of the system fails. These often have to be "centered" by bleeding one side or the other to "center" the piston in the valve.

This thread discusses this type of thing and may or may not be helpful for you:
https://www.ford-trucks.com/forums/892711-resetting-proportioning-valve.html

 

[snblinn]

Thanks.

Here is some added info:

About a month ago I was heading north from Virginia to Maryland to close the sale of my house. About 5 minutes into the 2 hour trip I needed to slam my breaks for an emergency stop. Two lights later my brakes failed. I made the trip downshifting and E-Braking.

Turns out I had a rusted line on the drivers rear line. I replaced the line, connector on frame under the drivers. I bought straight tube from Autozone, cut off one flared end, reused my flare nuts and reflared.

When I hit the brakes hard the left rear locks up. when I come to a stop the caliper releases after 5-10 seconds. This was before my Master Cylinder replacement.

I am wondering if this is a sign of the ABS pump going bad.


Thanks, Steve.

 

[Yupster Dog]

Thanks.

Here is some added info:

About a month ago I was heading north from Virginia to Maryland to close the sale of my house. About 5 minutes into the 2 hour trip I needed to slam my breaks for an emergency stop. Two lights later my brakes failed. I made the trip downshifting and E-Braking.

Turns out I had a rusted line on the drivers rear line. I replaced the line, connector on frame under the drivers. I bought straight tube from Autozone, cut off one flared end, reused my flare nuts and reflared.

When I hit the brakes hard the left rear locks up. when I come to a stop the caliper releases after 5-10 seconds. This was before my Master Cylinder replacement.

I am wondering if this is a sign of the ABS pump going bad.


Thanks, Steve.

That is the caliper going bad. Replace that caliper and you wont have that 5-10 second lapse.

That being said it is always good to replace in pairs with the brakes. I would replace both rear calipers at the same time.

 

[Trainmaster]

I just got rid of my 2000 that was rotting out brake lines in New York. Down there, you should give those lines a good looking over, especially where they come out from over the gas tank to make sure you have no other rotten spots.

And I agree with Yupster. Change those calipers.

 

[1955moose]

We've been seeing quite a few leaking ABS pumps here on the forum lately. Don't mess with the pump bleeding though, their touchy, and sometimes need a dealer or specialist shop to finish bleeding. If it turns out to be pump, you can either rebuild yours, or buy one done.

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