My brakes had become kinda spongy and low on the first pump so I bled the system including the proportioning valve the other day. Now it's worse. The pedal goes basically all the way to the floor on the first pump, when I pump the brakes again the pedal rises, feels very firm and the truck stops well. I bled the brakes again and I didn't see any improvement. With and without the engine running if I pump the brakes the pedal will firm up and stay that way, it won't fall to the floor slowly.

So should I try, try again to bleed... or is something broken on my 86?

 

Still sounds like there is air in the system somewhere since the pedal pumps up and won't creep to the floor. Possible that the master needs to be bled and then the wheels. If you are sure there is no air coming out when you bleed the wheels, then the master may be defective.

 

Did you just do any recent brake work?

Or did this just start happening on its own?

 

No work done.

 

You have air in the brakes somewhere. Master cylinder might have kicked the bucket.

 

Well, I am still having problems with this. Since I made this thread I have bled the brakes again, replaced the wheel cylinders (one was leaky) and shoes, adjusted the drums, bled again and again but still no improvement. Today I bought a new master cylinder from napa and bench bled it, then put it on and bled the brakes again... same double pump pedal. What else could be wrong??

 

brake booster

 

master cyl or brake booster i think booster is bad but i have bought bad masters so...

 

Wouldn't a bad booster make the brakes hard? I can pump the pedal firm with the engine off and then start it, the pedal will lower like a normally working booster

 

thats the most common is hard pedel but try this to test booster
Press the brake pedal a couple times it should become harder to push than start car in a few seconds pedel schould get softer

sorry i didnt read ur hole post

 

but really u may just still have air in lines

 

or the one thing i havent seen yet is he could have a collapesd brake line somewhere

 

a bad brake booster will not cause you to have to pump the pedal twice. It would just cause the pedal to become hard to push.

I would say it was your master cylinder but if you changed it then I don't have any other ideas. sorry.

 

I had a problem like this when I had a manual nissan 240sx. I had a dead pedal that I would have to pump before it got any braking force. And I replaced the master cylinder and also the slave cylinder. I forget which one fixed the issue though so, yeah...

 

The only other component is the brake lines. Maybe you have one that has a weak spot and is balooning out.

 

I had an issue like this in my 82' pickup awhile back. Wasn't quite as bad as your saying, turned out to be one of the brake lines in the front would slightly swell. How I saw this was bleeding the brakes, while they were being pumped I could see one swell and in between each rib, you could see it was slightly cracked. Put on stainless braid lines, problem gone.

 

Did the proportioning valve bleed good? Rear brakes adjusted right? On that matter, does your emergency brake work good?
If you drive on a hill and stop, holding the truck on the hill with the brakes, does the pedal sink down at all?

 

a good way to check to see if the line is swelling is holding a mirror behind the hose and having someone build up pressure in the line

 

Bad master cylinder. Same thing happen to my 87.

 

look at the brake booster, vacuum lines to the booster . A bad booster can make the brakes feel too touchy or soft. These are just ideas from things I've run into. it is more common for them to make it really hard to push but i have had soft peddle to