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Hey all.
My 97 F250HD has been sitting for the past month and a half. Started it up yesterday, and the "Brake" and "ABS" lights on the dash were on. Also, the brake pedal had lost almost all of its pressure. It had a fair amount of travel before, but now it makes it to the floor and will not lock the brakes up at speed (i tried).
The brake fluid in the reservoir was low, so i topped it off, but the issue persists. I pumped the brakes several times and couldn't find any leaks. It holds pressure fine once its built up. With the engine off, pumping the brakes builds plenty of pressure, and the petal is firm. I'm not sure where to go from here.
I did find this forum, but there's no resolution to it. I am wondering if the ABS module could be the issue.
Thoughts?
When the brake fluid is too low the float switch in the master cylinder will activate the Red Brake lamp which in turn will trigger a yellow ABS lamp. After you filled the master cylinder did the Red and Yellow lamps turn off?
If yes and you still have a spongy brake pedal then the root cause of the low fluid, a fluid leak, has allowed air into the system. The usual cause is a leaking rear wheel cylinder. The fluid leak is hidden behind the brake drum.
When I filled the master cylinder, neither the red "Brake" light or the yellow "ABS" light turned off.
I have not inspected the rear wheel cylinders, I'll search there first if nothing else comes up worth checking.
Agree with the rear cylinders. A lot of dirt and brake dust can absorb the fluid and hide the leak.
When I had the same failure, and could not find a leak, it was the flex hoses on the front that had corroded but were still attached to the rubber. So much dirt and grime, the brake fluid was absorbed and didn't show a leak.
Check the float in the master cylinder. Sometimes they absorb fluid then sink to the bottom. That keeps the Red brake lamp on as well as the Yellow ABS. While that is not the cause of your soft pedal/sinking pedal but needs addressed.
Pulled my driver rear drum today. Yikes. Glad I did, there's no shoe left! Absolutely soaked inside, good call on the wheel cylinder guys. Now. How does this drum look to y'all? Replace, resurface, or it's fine?
Update. The passenger side was even worse. There was no pad material left and there was a awol spring causing havoc inside, and it destroyed the drum, so new drums it is.
