Booster problem? Pedal doesn't return.

[Spyder]

I really want to take this thing for its first drive and sest the rings.

Brake pedal isnt returning past about halfway. Bottom half of the throw it feels fine but the top half it swings free after a partial return.

It sits low enough without pressure the brake lights come on. I bled them and got air out, no change in pedal feel. I'm guessing I messed up the booster when I had it off to paint the engine bay Bidy color. I don't mind just replacing it if that's the easiest, but all the ones I'm seeing are different than this lower profile one and none are low cost.

Ideas to check or try before I replace it, and if I replace it with the bigger version I'm seeing available will that work?

Car is a factory disc power brake car.
Here's what's in it now. Worked fine before the engine came out so I assume I broke it, put it together wrong, or missed putting something in that should be there.

 

[Challenger RTA]

Just has some bake problem on an other car of mine. Did the same thing as yours. Right a way I was going to change the booster and master cylinder. Diagnose first. Is the booster holding vacuum? When at idle can you pull the vacuum hose off the booster and is there vac? Check the check valve see it it is working. Has vac and holding vac. Master cylinder working Does it pump up and can you bleed any fluid out? I could bleed mine but it was only a 50% steam as usual. Is the fluid clean? Even with fresh fluid it was the same. Mine was a little dark. Ended up the line where flushed from the constant bleeding. When moving car very slowly will it stop when using the brakes. Yes mine did but it was not full pedal. Pedal would kind of pump up but when done only about half way up when done.
Ended up finding a rear wheel cylinder was not working. Replaced it and all is good.

 

[Xcudame]

Definitely check every where for leaks! Including the brake booster (fluid and vacuum)! And make sure all the lines are bled really well once no leaks are evident.

 

[Spyder]

I bought a temp one from Summit, the Right Stuff booster and master combo, and hate it. Don't think I'm going to use it, and considering just going manual for now until I can figure out a rebuild for my booster.

If I stick a 15/16" master for disc/drum on the firewall, and buy an adjustable rod, the current brake lines I should be able to make work without bending and I can at least go out and test drive the new engine while I figure out the new brake problem. I'd want to get the stiffening plate from Dr. Diff as well if I go that route.

Harmon sells rebuild kits for this booster...at $345 bucks plus another 40 something for the tool to disassemble/assemble...

 

[Spyder]

Just has some bake problem on an other car of mine. Did the same thing as yours. Right a way I was going to change the booster and master cylinder. Diagnose first. Is the booster holding vacuum? When at idle can you pull the vacuum hose off the booster and is there vac? Check the check valve see it it is working. Has vac and holding vac. Master cylinder working Does it pump up and can you bleed any fluid out? I could bleed mine but it was only a 50% steam as usual. Is the fluid clean? Even with fresh fluid it was the same. Mine was a little dark. Ended up the line where flushed from the constant bleeding. When moving car very slowly will it stop when using the brakes. Yes mine did but it was not full pedal. Pedal would kind of pump up but when done only about half way up when done.
Ended up finding a rear wheel cylinder was not working. Replaced it and all is good.

Master and wheel cylinders all check out fine. I don't really want to run the engine much until I can get out and drive it, brand new engine and rings aren't seated yet. Checked vacuum today and it pulls 16", booster seems to hold it fine, and check valve suck blow test worked fine. I don't see anything obviously wrong with the system but I don't have much experience with them either. Bleeding the lines seems normal, works fine, the pedal just doesn't rebound enough to turn the brake lights off. I was out tinkering with it tonight until 9:30, pulled the booster back off and popped the retainer ring off to look inside again and I don't see anything obviously wrong.

 

[Challenger RTA]

1 Most instances of a hard pedal come down to a failure in the power boost system.

2 Another cause of a hard brake pedal can be a brake caliper that is stuck or seized.

3 Sinking pedal If while sitting at a stop you find the pedal slowly sinking to the floor with your foot on it, you have a master cylinder that is just starting to go bad, or a leak somewhere in the system. But if no leak can be found, it is most likely just one of the rubber seals withing the master cylinder allowing fluid and pressure to sneak by or air in the line.

What you described is non of the above.
There is something out of spec. Not allowing components return to working state. Worn rotor, drum, pads, shoes, wheel cylinder, caliper, parking brake not working correctly and worn wheel bearing.

 

[Bret Schneider]

If I understand correctly, the problem is the brake pedal doesn't show any sign of resistance until the pedal is halfway down.
If that's the case it sounds to me like you either have a broken/jammed spring in the booster or the brake pedal to booster rod is misadjusted/broken/out of place.
The booster spring provides the initial brake pedal resistance so if the pedal is flopping around there's something not right there.
You mentioned you had the booster off. I'd begin retracing my steps there.

 

[Challenger RTA]

Here are some other brake issue to read up on that might apply.

Brake issues

More on brake issues. This is to help others with problems. I will elaborate from an other post a little more. Non ABS. The story goes. My son had a car problem used mine for bit. When he got it I told him I need to look at the brakes. I smoked the tires and brakes. Someone pulled out in...

www.forebodiesonly.com

 

[Xcudame]

Bret may have just found your problem with the booster spring.

 

[Spyder]

Yep that makes sense. I have it apart in the shop I'll get out later today and tinker more. I definitely think I just did something wrong putting it back together and reinstalling it.

 

[Challenger RTA]

putting it back together

Been there done that. It worked when I took it apart. Now it won't work after I put it back together. I do it twice to do it twice as nice! I take picture too. And it still come out wrong. OH wait! there upside down!