Problem with the Brakes....

I bleed out my brakes yesterday. Pedal feel was great. Then I started the truck. The pedal went straight to the floor... Tried bleeding them with the truck running just to see what it would do... No different...

I pulled out the vac check valve.... It is working properly. When pumping the brakes with the engine running, the truck starts to die out. When we clamped off the vac line to the booster the brakes felt a world better. Its ike it has a vacuum leak... I am guessing the brake booster is shot... any ideas???? Anything else i can try to trouble shoot before throwing more parts at it????


Thanks in advance...

 

You are the man.... Thank YOU!!!!

 

OK, tested it all... pedal builds pressure fine when engine is off. Start the engine and the pedal goes to the floor. Try to pump it up and it still goes to the floor. I have the engine running with the pedal pressed, shut the engine off, wait 30 seconds, and it pushes to the floor...

Is it a safe bet that the booster is not holding an air tight seal??? A new booster is $250 at Napa, and I hate to take on the expense let alone the hastel of changing it unless I can pin point it to that being the problem first...

 

why were you bleeding the brakes,did you replace something?if the booster was bad,from leaking vacuum internally,it would basically feel like it does when the engine is off.i've seen people bleed there brakes and push the pedal all the way to the floor to bleed.this will sometimes mess up the seal in the master cylinder, from contaminates that have built up in front of the seals.

 

I had to change the Driver Front Caliper.

So if the booster was leaking it should be real stiff even with the engine running?

When I changed it all, I opened all bleeders and flushed new fluid thru the entire truck. So I am hoping there is no dirt left in the system.

What could it be causing the pedal to have NO pressure once the engine starts???

 

Also the engine almost dies out when you pump the brakes...

 

was the brakes acting like this before you replaced the caliper?

 

The truck was a basket case... sitting for 4 years. Take a quick peak at my build thread and you will see. the first pic is the way it sat when I purchased it.

The caliper was froze solid. I have yet to drive the truck. Just in and out of my garage since I got it running.

 

if all of the air is out of the lines,and its still going to the floor,i would take a look at the master cylinder.