Robert F150

I completed work on the ignition system and went to start my truck up after sitting for a month.....ran great, put my foot on brake to shift and it went to the floor....ugh.
Master cylinder was empty with no obvious signs of leaks. Ended up replacing master cylinder and hopefully bled it correctly. Now I still don't have any pedal pressure but when I unhook the vacuum hose on the booster I do. I always thought a bad booster gives you a hard pedal. Am I missing something????

DarrinT04

did the brake fluid leak out again? if so i would look into a busted brake line

Robert F150

No, reservoir hasn't lowered. Oddly, I couldn't get any fluid to come out of bleeder on L/R brake.

DarrinT04

you might have clogged brake hoses

RLXXI

Did you bench bleed the master cylinder before you installed it on the truck?
.

Robert F150

I did, but first time replacing one, so may not have done it right. Luckily, this is just my get around town truck, so I think I'll let it sit for a week, clear my mind and then get back at it.

Thanks for the replies.

raski

Does the pedal go to the floor or you have no power assist?? What could have happened, since you saw no leaks, the fluid could have leaked out the backside of the master cylinder. The fluid can ruin the booster then it gets sucked into the intake through the vacuum line and burned in the engine.

Robert F150

That makes sense. Pedal goes to the floor without building pressure while pumping. I may try a new booster before throwing in the wrench.

raski

If it goes to the floor with engine off, it is not the booster. You should have a high, firm, hard pedal to begin with. You either have a lot of air in the system or your new master cylinder is faulty and I have had a new one bad out of the box before. I would bleed all four wheels first. BTW- to check the booster, first you need a firm pedal with engine off. Next two checks for the booster. With engine running, foot off the pedal, there should be no hissing sounds present. Next, turn off engine, wait 10 minutes, press your pedal repeatedly. You should get atleast 3-5 power assisted pedals before the pedal firms up if the booster is good.

Robert F150

*UPDATE*
Truck is on the road with working brakes.
I guess there was blockage right before the L\R wheel cylinder. Instead of using my hand pump bleeder, I had a buddy pump the brakes. Something shot out fast and we're rolling now.

Thanks for the tips guys.