Recently, on my way home, I fairly suddenly suffered reduced braking power. The truck would slow a little when I pressed the brake down about as far as I usually had to to slow quickly, and it pushed down way too easy. I've bled the whole system, but I doubt that's the problem, since I haven't broken the system anywhere since I've had the truck. The only brake work I've done has been new rotors/pads up front.

If I pump the pedal aggressively, it builds pressure and behaves like normal for about one press, but the pressure bleeds off quickly. If I stomp it all the way down, I get weak braking in the rear, and the front still locks up if I'm on anything soft, like grass or mud. I know rear wheel cylinders can cause problems, but there's no leak back there, and if I pump the system up, the back end still does its job.

Am I correct to blame it on the master cylinder, or at least make that a place to start?

 

Bad seals in M/C.

 

I had the same thing happen on my 81 F-100 and I know it's not a newer truck but for the most part it's the same. I changed out my M/C and it fixed my problem. That thing stops better than my 95 F-150and it's got new brakes all the way around.

 

It's a cheap enough repair, as repairs go, but it's going to be a pain in the hindquarters to bleed afterwards, especially since I pretty much fly solo, and brake bleeding is a two+ man job. Heck, I'd settle for lady-help, or even a beagle if it could be trained to push the pedal all the way down.

 

When I did my 81, I'd pump up the pedal and then jam a rod on the brake pedal and the seat.

 

Sounds like the "idle stick" I use in my F-250 with the 351...

 

I bleed solo all the times without issues, and I'm an old geezer.

Buy an one man brake bleeder kit.

Be sure to bench bleed the master cylinder first before putting it on the truck.

 

What do those kits usually run? If it's more expensive than buying lunch, I'm better off feeding a friend in exchange for an hour of their time.

 

About $5-$10.

If you prefer not to, just find a length of hose that will fit the bleeder tightly. Vacuum hoses work pretty good. Then find a good sized jar filled with clean brake fluid to ensure there will be no air sucking up when you are pumping the pedal.

 

I find it odd that this problem came on all of a sudden. Yes the seals do go in a master cylinder and when they do, you will lose pressure and your pedal will sink to the floor. But to suddenly and drastically lose braking to that extent. Have you checked to see if you are losing fluid when you are applying brakes and losing pressure?
I think air in the line is not the issue and if you've checked the system well, front to back and there are no leaks and confirmed this by fluid levels then the mater cylinder needs to be looked at. I think you can just buy repair kits for them as well rather than change.
Which truck is having the problem. Your 95 will have abs, and I'm not overly knowledgeable about abs and how it works, so I am not familiar with problems which may arise due to faulty abs components.
my 2cents

 

It is worse now than it was when I first noticed it. It sort of came on mid-trip, and has deteriorated a bit. At first, it only took two pumps or so, now I have to rapidly pump it a half dozen times to get real braking power. More recently, I've also got a squeaking-whistling type sound when I push the pedal down quickly. That's another thing that's making me think master cylinder, unless maybe I've got a vacuum leak to the brake booster, but if that were the case, I would have been hearing the sound since I started having problems, not just now all of a sudden.
No fluid loss anywhere, whether I'm pressing or not.

I figure for thirty bucks, I may as well just put on a reman. The repair kits cost almost that much.

It's the '95. I'm not terribly familiar with ABS myself, though all but one of my older trucks had it. Of course, it didn't work on any of them, and the ABS light was just covered with black electrical tape to hide it. Seems the ABS system should have been engineered in such a way as to be failsafe in this regard?

 

I forget how cheap some parts can be had in the U.S.
If you can get a re manufactured MC for that price, then do that for sure.
It is sounding like the MC is your problem. I do know that if the booster was the issue, the brakes would be hard to press(the opposite of what you are experiencing).
As for the ABS...
I have the rear abs in my 150 and hate it, hate it, hate it!!!!
My Bronco has four wheel abs but the truck will not see the road until next spring so I can't comment on that system yet.

Well, keep us in the loop and let us know what happens with your truck

 

I've never been a huge fan of anti-stop brakes myself, but they don't seem to work on any of my vehicles, so I'm happy. Guess I'll be doing the MC next time I've got to drive into town to pick up parts I ordered in for the tractor. The NAPA here has it in stock.

 

Turns out it wasn't the MC.

Yesterday, I blew out a brake line while hauling a lawnmower trailer somewhere on my way to the farmers market with a load of produce. Brake and ABS lights came on, and the pedal got even worse than it had been. Still had front brakes--thank God for the partitioned reservoir!

Picked up a brake line and bottle of DOT3 at the NAPA where I was set up, but I couldn't get the old line off with the tools I had on hand. Picked a heck of a day to borrow the vise grips out of my truck and forget to put them back...

Anyway, I replaced the line, flushed the other side(the brake fluid was a healthy tar-black), and bled them thoroughly. Now, my pedal is as firm as any '80-early-90's F-series I've ever driven(which isn't nearly so stiff as those damned Dodges!), and after a few times shutting off and starting up, the brake and ABS lights went out.

I never suspected a brake line or leak, because the reservoir was just a hair above mawhich is where it was after I pressed my front calipers when I redid my front brakes), so the question now is, is it possible for a metal brake line to fail in such a way that it either sucks air without leaking fluid, or allows pressure to dissipate without losing fluid for a couple weeks of routing driving before it finally blows out?

 

Sounds like that portion was restricted. As you kept driving, something had to give with that restriction...the brake line gave way.

Old brake fluid contaminated with moisture will turn to goop eventually. My '78's M/C had goop stuck on the bottom of the bowl! Replaced it and blew all the lines out, all is well.

People need to know that brake fluid, like any other fluid, MUST be changed/flushed at regular intervals. New brake fluid = firm pedal.