I haven't made any brake repairs since about last July(replaced RF caliper and rotor, didn't replace LF because I couldn't get the rotor off, saved that trouble for another day, since the right side was good enough for me). Brakes have been working just fine since repair.

A few days ago, I noticed a spongy brake pedal. She was still stopping ok, though. Yesterday, I was getting off of the highway, coming to a red light, with a vehicle in front of me, pressed the brake pedal, spongy at first, then all the way to the floor, brake light and ABS light on dash came on and I barely got her stopped short of the tailgate of the truck in front of me. Cautiously drove to a parking lot, noticing that after a few seconds or minutes of driving, I had a good pedal(semi-stiff, that is), then she went back to the floor. Once safely parked, I checked the brake fluid. I thought, for sure, that I'd find the reservoir low or completely empty. It wasn't(level about halfway between full and add). After completing my grocery shopping, started the truck, no warning lights on the dash, good pedal before I put her in gear. Slowly backed out of the parking spot, both warning lights came back on and pedal went back to the floor.

Since I had a bunch of perishables in the truck, and since I have an aversion to working on cars in parking lots, and because I'm a bit of a daredevil(read: hard-headed moron), I, very carefully drove her home, making sure to allow plenty of space between vehicles, and plenty of time for stopping.

Again, after a few miles of driving, she had good pedal for a second, followed by very spongy for a second, followed by pedal to the floor(but still stopping).

I didn't check the fluid level when I got her home last night(had groceries to put away, dinner to make, then forgot about the issue). This morning, the brake reservoir is still about halfway between full and add.

Thoughts? Master cylinder? Prop valve? Booster?

 

Sounds a lot like a failed master cylinder.

 

Big job? Keep in mind that I live in the lake effect snow belt of NW Indiana and that it's 30*.

 

Working outside in the snow and the cold makes ANY job somewhat less than what I would consider "pleasant".....

It's two bolts, two lines, and maybe an electrical connector. Need to bench-bleed the new master, and you will likely have to bleed the entire brake system as well, to get all the air out of it. (be prepared for bleeders to break off.......) That is just gonna suck working outside in the cold...... If you know someone that has a garage you could borrow for a few hours, that would make your life a WHOLE lot more pleasant.

If you have the option, pay someone else to deal with it.

 

Any brand of master cylinder that I should avoid? From a bit of research, I see that reman masters are crap. Duralast? Dorman(does Dorman make anything that's not crap)? OEM?

 

I am not really a fan of Duralast, or Dorman.... Cardone is kinda hit and miss....... Not sure who else is out there any more.....

May wanna have a look at the rear brake line first though. They tend to rust out, and break, back by the gas tank..... the fluid doesn't always make it to the ground right away...... so it isn't an obvious leak..... fluid loss may not be apparent right away either...... Wheel cylinders are also famous for that......

 

Ugh! I was afraid you were gonna say that(the rear line). If it was a wheel cylinder, wouldn't it be losing fluid rather quickly?

Also, thoughts on AC Delco masters?

 

I know ACDelco makes good steering components. Why not upgrade to the hydro boost setup? It will be more money but you will have better brakes.

 

I don't know what hydro boost is.

 

Other than getting under the truck and climbing, somehow, to the top of the fuel tank, how do I check the rear line? Forgive my ignorance. I've never done this before(replaced rear brake lines).