Brake lights stay on until I pull up on the brake pedal

[myf16]

1996 XLT 4WD 4.0L

I replaced the brake light switch but the problem persists. The pedal does not reliably come back up fully when the service brake pedal is released. It's maybe 1/4 inch short of fully up. I have not noticed any brake dragging or mpg problems.

Is this a sticky master cylinder? Bad brake booster or valve? Something else?

 

[Pete Deering]

1996 XLT 4WD 4.0L

I replaced the brake light switch but the problem persists. The pedal does not reliably come back up fully when the service brake pedal is released. It's maybe 1/4 inch short of fully up. I have not noticed any brake dragging or mpg problems.

Is this a sticky master cylinder? Bad brake booster or valve? Something else?

Sound like , you did not adjust the brake light switch correctly the first time.
The MC piston pushes the petal back.
The readjust brake sw

1996 XLT 4WD 4.0L

I replaced the brake light switch but the problem persists. The pedal does not reliably come back up fully when the service brake pedal is released. It's maybe 1/4 inch short of fully up. I have not noticed any brake dragging or mpg problems.

Is this a sticky master cylinder? Bad brake booster or valve? Something else?

1. Did you reinstall the black bushing on the shaft?
2. The brake petal assembly , sometime breaks. There has been a few post about that issue in the forum

 

[myf16]

Sound like , you did not adjust the brake light switch correctly the first time.

I don't see any adjustment on the switch, nor do I see any way it could move. The brake lights always worked correctly until the last week.

1. Did you reinstall the black bushing on the shaft?

Yes.

2. The brake petal assembly , sometime brakes. There has been a few post about that issue in the forum

Everything looks normal but the pedal does not rise the last few mm when the pedal is released.

 

[Pete Deering]

I don't see any adjustment on the switch, nor do I see any way it could move. The brake lights always worked correctly until the last week.


Yes.


Everything looks normal but the pedal does not rise the last few mm when the pedal is released.

The only adjustment is on the brake booster rod. See attach.

1996 XLT 4WD 4.0L

I replaced the brake light switch but the problem persists. The pedal does not reliably come back up fully when the service brake pedal is released. It's maybe 1/4 inch short of fully up. I have not noticed any brake dragging or mpg problems.

Is this a sticky master cylinder? Bad brake booster or valve? Something else?

See attached

 

[myf16]

The only adjustment is on the brake booster rod. See attach

There’s no reason the adjustment would have changed after 25 years so I guess my brake booster is failing.

 

[myf16]

On further thought I think the master cylinder collected some corrosion impeding the last bit of piston travel. Maybe I will change the master cylinder and maybe I will live with it. In the meantime I will see if a bungee cord can provide enough upward force on the pedal.

 

[myf16]

This problem disappeared on its own. It must have been surface rust due to heavy rain last winter.

 

[gatzdon]

On the Brake Pedal bracket, there is supposed to be a small rubber pad that hits the light switch (there is also one on the clutch pedal if you have a manual). After 20 years, these disintegrate and fall apart.

They look something like this (on amazon Amazon product ASIN B0BL7LNFCT )

When it falls off, the pedal won't 'come all the up to depress the light switch'. If this is your problem, very cheap fix.

 

[myf16]

My brake light switch has an internal plunger:

https://img.go-parts.com/catalog/brand/standard-ignition/full/414E1F1.jpg

So I'm pretty sure the problem was friction inside the master cylinder.