At start up my 96 has a spongy brake pedal. As soon as it runs a few minutes it gets harder. But if I turn it off, it goes back to spongy for a minute or so. I did bleed the brakes with no change and the pads and shoes are good. After running a few minutes the brakes work fine. Any ideas? Thanks for any help.

 

Vacuum pump or a vacuum leak. Check all the hoses from the vacuum manifold.

 

A vacuum issue should cause a hard pedal but it is worth checking out. How are the read brakes for adjustment. they should be adjusted up a bit tigher if they haven't been touched in a while.

 

My pump locked up on me once and the pedal was soo hard it was all I could do to stop the thing. Tim is right you want to adjust the drums and check the calipers.

I am also wondering if the Master cylinder is going out. If you press on the brake at a stop and hold it down but not too hard (usually I press lightly and very lightly let off a little without releasing the brakes and do this back and forth, sort of like feathering the brakes) and the pedal starts to sink to the floor slowly then the MC is going bad. You will have to do this while it is running unless you are the Hulk. It may take a while of doing this if the MC is just now developing a leak in the seals but will definately get worse as it wears. It will finally get so bad that the brake will, when pressed, grab then hit the floor and you have to pump the brakes to get it to slow down.

Note: If it ever gets this bad quit driving it. Please.

 

if you just bled the brakes, i would start there. i don't believe in coincidences, meaning that they just so happened to have a completely unrelated problem after working them. so if the brakes were ok, then you worked on them, in my wrenching experience, 99 percent of the time, something went wrong, double check over everything you touched.

 

Skittle has a good point. If you bled them and possibly ran the bowl dry it could have possibly sucked some air in the lines and you not realized it. That has definately happened to me.

 

Dooh! Yep, the peal will get hard with a vacuum leak. Sorry
I got my brake assist types mixed up in my dumb little head. That reminds me:
Bob, does your van have vaccum assist or is it hydraulic (Power steering pump). Don't vans have power brakes from the PS pump? IDK.

 

didn't know ford used any hydro boost setups. work on them a lot in the military and some gm products recently. guess it's only on vans?

 

i wanna say hydroboost was on the f-superduty's, also. atleast thats what i think im regurgitating from reading a previous post.

 

Another possibility that hasn't been brought up is the front brake hoses themselves.

Mine deteriorated from the inside. No leaks, no cracks, no brittleness, no visual cues of any type that they went bad and began affecting the rest of the system. I didn't find this out until AFTER the accident. I've posted on the damage before, so I won't go into it.

I had around 112,000 miles on the truck when all this happened. If you have that much or more, AND you still have the original brake hoses, you might want to swap them out just because. Better safe than sorry.

It's the bad stuff you can't see that bites you in the a$$ the hardest.

 

Thanks for all the replies.

Cuda it does have the hydraulic.
What confuses me is that it is only a problem at start up. After that it is fine. My 97 doesn't do it. The truck only has 88k on it. This didn't start after I did any work on it. I bled the brakes trying to fix it but it had no effect. I was thinking master cylinder but it is fine after it runs a few minutes. The problem is I pull heavy trailers and if something is going out I want to fix it before there is a problem

 

Bob, Next cold start try moving the steering wheel to see if the power assist is low. If so, you could try flushing the fluid but the PS pump may be getting weak.
Look here:
https://www.ford-trucks.com/forums/4...steering+flush

 

Oooohhhh hydraboost! different ball game!!

the problem is definately in the booster circuit not the brake system. low fluid, weak pump (though weak pump you would think would be a problem after warm up) check thlink Jim gave you and see where your at then.