My ABS and brake warning lights came on about 3 days ago. Took it to my mechanic who was unable to decode problem, as only a dealer has the special magic box! Brake fluid level fine, all brake lines look OK, truck brakes just fine.
I researched online, seems a common problem is a malfunctioning sensor.
Long story short, today while driving around town, I noticed brake pedal getting a little mushy and then a little mushier, so I nursed it home, checked underneath and when I got to the right rear wheel, there is a large puddle of brake fluid underneath and it is was dripping from the bottom of the drum onto the ground.
What do you guys think? (I know I have a problem, but what specifically?)
I purchased this truck from the origial owner at 160K miles with all of the mx records (He pulled a 5th wheel house trailer with it).
In checking through the service records, I find that he has replaced front braked 3 times, while there is no record of any rear brake replacement other than turning the drums about 20K miles ago!.

PS: I forgot to mention that I bought the truck in Muskegon Michigan, so it does have "some" rust underneath!

 

LOL, replace the entire rear steel line, it is rotted. Mine did the exact same thing about a month ago.

I used (2) 60" lines, and (1) either 24 or 30" line, and 3 connectors, 3/16" is the size.
That took me all the way from the front junction block by the front tire to the proportioning valve back by the spare.

Good luck, not a bad job, I did not drop my fuel tank, I will tuck things up nice behind there whenever I do need to drop my tank.

 

I would think you may have a wheel cylinder leaking.

 

If the problem is not your brake line, then check the rear brake cylinder. Numerous threads about brake jobs and how to get the rusted/stuck drum off.
Just use the search tool for this forum.

 

Brake line look fine all the way to the drums.

 

Sounds like a leaking cylinder.
While you're at upgrade the rear cylinders to part number 37337 at any auto parts for under $15 each. A qt of brake fluid and an hour of your time and I guarantee you love the way it stops. It is a direct no hassle swap.