No Brakes!!! Need Help!!!

[csm672]

Hi, I have an '85 Toyota 1 ton 2WD. It has a braking problem that I can't seem to fix. It started about 3 months ago. I would pull up to a stoplight and my brake pedal would slowly go to the floor. Now it has progressed to the point that when I push the pedal I get good brakes for about 1 second and then the pedal hits the floor and I have no brakes. I had a leak in my load sensing proportioning valve (I think- It had some fluid in the boot) so I replaced it today. I went to bleed the brakes and can't pump them up enough to bleed them. The pedal goes straight to the floor. I get fluid to every line but it just won't hold the pressure on the brakes very long. I did notice today that with the engine running, when I pump the pedal rapidly the idle gets rough. This has to be the booster. I unplugged the vacuum line and plugged it up and it ran fine when I pumped the pedal (but maybe this is normal- I don't know!) I have no leaks and am pretty certain all the air is out of the system. Could a booster cause the problem I'm having? The master cylinder was replaced a couple of years ago, but maybe it is bad? Any help would be greatly appreciated. Thanks, Casey

[sonofmayhem]

i had the same problem with my 85 1/2 ton, i replaced the master cylinder and they work like a dream.

[smasheromalley]

The sinking pedal problem is probably the brake master cylinder. Ive run into it a handful of times over the years and it has always been the brake master cylinder.

[texas12]

I'll 3rd that on the master cylinder vote. My LSPV was also leaking and dealer wanted over $200. Been running without it for the past 6 months. I did replace the master cylinder for the same symptoms that you are having.