Trying to Solve Some Brake Issues

[shorty73]

So I’ve had my truck about 6 months now, but only had it on the road for about 2 due to various problems. Right now I’m focusing on brake issues and need a little help. I did some searches and didn’t come up with anything. First one should be simple: how does the brake warning light come out of the dash? I think the bulb is burned out as it doesn’t light up during start. I reached under the dash and tried pulling and pushing on it, but didn’t want to break anything forcing it out. 50 year old stuff tends to do that.

Second, the brake pedal goes down about 1/3 the way really easy, then gets very firm and holds (no slow drop to floor). It’s disk/drum with power assist. It definitely takes more effort to stop the truck than I would expect for the setup. If I pump the brakes 2-3 times, the pedal comes up a little ways, the pedal feels more like it should, and I can stop the truck pretty easily. The pedal also holds and doesn’t drop. After I turn off the truck, I pulled the vacuum check valve out of the power assist and I get a loud woosh. Seems like the unit is holding vacuum. So what do I have, a bad master cylinder or bad booster unit? I’m leaning toward master cylinder but I don’t want to throw money in it unnecessarily. Thoughts?

Finally, is this a dual or single diaphragm booster? From reading, it sounds like I should have a dual unit, but this sorta looks like a single?

Thanks in advance.

[DuckRyder]

Looks like a singe diaphragm booster.

If the pedal comes up when you pump it and does not sink, I would bleed the brakes first. Do you know when the brake fluid was replaced last? What color is it (the brake fluid))?

So this is an F250 with factory 4 piston calipers up front?

[shorty73]

The truck seems all stock as far as I can tell, but I'll have to look at the calipers later. It is a F250 with 360/c6. I bought new brake lines cuz they look pretty ratty so I'll replace and bleed the system. Hopefully that fixes it. The fluid looks good in the reservoir but this was a barn find flip. It could have been low/dry and have added fluid, but it seems unlikely because I haven't seen any leaks and the level hasn't dropped any since I started driving it around. It might be a bit before I can change the lines and get some help with the bleed, but if that doesn't fix it, I'll get back here. If someone can tell how to get that brake warning light out without breaking it, that would help. It started pushing out the front of the dash a little, but it just didn't' seem right, so I quit.

[shorty73]

Got one line replaced. Getting the flare fitting loose was a pain and involve vice grips. I'm guessing the other side will be the same. I also got the brake warning light out of the dash. The assembly behind the dash twists counter clockwise to come out. Checked the bulb and power to the socket and it was fine. So I kept looking and it turns out someone disconnected the wiring at the warning switch mounted on the frame rail. It's been disconnected for awhile and the whole area is coated with oil and nasty. They probably got tired of the light being on, or maybe were trying to sell it and didn't want it on. I didn't have time to clean it up for testing yet.

The calipers are dual piston and say "Dayton" on them. Pretty beefy setup. I expect once I get stuff fixed, this things gonna have some stopping power.

[shorty73]

Brakes are up and working fine. The back brakes had air in the lines. It wouldn't bleed at first but a stomp on the pedal and nasty fluid shot out. All the lines and the reservoir were nasty. It was funny because the reservoir fluid looked fine but the bottom was coated with silt or whatever. Anyway, problem solved. The warning light I couldn't get to reset, that will be project for another time. Thanks DuckRyder for suggesting to try bleeding rather than look to replace master cylinder or booster.

[Redcrew71]

yep nasty stuff comes out. fluid in resovior would always look good but never gets to brakes that are working. my 71 f250 had drums all around. easy to bleed. great pedal movement after bleeding. lf bleeder was siezed though so could not do that one. replaced all the others.