I have a 99 Expedition. The brakes work as far as stopping. However, the ABS light is on, and recently, the pedal will sink slowly to the floor when sitting at a light. If I repump the brake, it will go back up, but start to sink again.

I don't hear any vacuum leaks in the cab, and I don't see any fluid leaks in or around the brakes and lines. The fluid level is a bit below the max, but then again, it's been on the road a long time.

I've seen numerous posts with this issue, but many trial and error fixes. Any ideas.

Thanks,
Brian

 

If there is no fluid leaking anywhere, especially at any of the wheels, then the master cylinder seals are internally leaking and the MC needs to be replaced.

 

When was the last brake pad replacement and who did it?
If the system was not bleed properly, a soft pedal as you describe is common.

 

Definitely the master. You may find fluid in the booster as well.

 

I'll take a look at the master. Brakes were about two years ago. Going to have to start soaking the fittings on the master. One of them looks a bit rusted up.

Thanks!

 

Now is the perfect time to treat yourself to a nice set of flare wrenches.