But doesnt a bad brake booster not apply any assist? Therfore its the same with the truck off or on?

My brake pedal is always super super stiff with the engine off... what he is experiancing is normal, IMO... But I have never tried to bleed brakes with the engine off, as it works soo much better with them on..

 

I'm just guessing because the only difference in the braking system with the engine on/off is the vaccum being drawn for the booster.

 

That's funny... I never tried bleeding them with the engine running. :pat:

I've always bled them with the engine off. Not that it would be bad to do it with the engine running, it just never occurred to me to try.

I'm living proof that it can be done properly with the engine off.

 

There's no need to run the engine to bleed brakes! With the car running you will get ASSIST like someone is helping you push the pedal that gives you a artificial feel. With the car off you'll get more FEEL (manual) as to the pressure in the system. As to your problem. What happens to the pedal (engine off) if you just held it in (no pumping)? Does it fade down and stay down? If that happens I would suspect the MASTER CYLINDER (leaking internal seals letting fluid pass). now imagine the same process with the car running with vacume boost, that leaking master cylinder would now leak twice as much. Causing a rapid pedal drop. I would bleed them again (thats free) making sure all/most air is out. then retry that test. My .02 cents.

 

When the truck is off... I have plenty of pressure on the peddle. It never goes down. When I start it, it's like someone just cut a line. Drops to the floor and never builds up. Shut it off again and 3 pump it hard as a rock again. Start again and it goes to the floor. ???

I only bleed them with it off and I never did the lspv…Didn’t know I had to. I’ll redo this weekend and bleed all lines again starting with the longest to the shortest and lspv last with the truck running and see what happens. Thanks!

 

If you switch the lines from the front to the lspv....you won't have breaks when started

That's all it was. FYI

 

WEll, glad you got it figured out!! Congrats!!

 

That makes sence