So the other day on this hatch shell I've been building I got around to bleeding the brakes. I out a new mc on cause I couldn't get the brakes to bleed but once I replaced it they did. I started thed car and the brake pedal had zero pressure at all. But when I turn the car off it had adequate pressure. Could this be a bad booster or a vaccuum leak somewhere?

 

more likely a vacuum leak, if you have no pressure when the car is on. check all your vacuum lines to your MC.

 

No vacuum leaks its all nice n tight

 

I just unhooked the vacuum line that goes the the brake booster and now the brakes feel fine?? Is it possible to run the car this way?

 

hmm... did you bench bleed the MC before putting it in the car?

 

x2^^

 

I bet it's a bad booster and yes you can drive without it plugged in, as long as you clamp off the vac hose. Your calf is going to get sore.

 

no pressure is in it goes to the floor, or no pressure as in there's no difference from when its off? if it goes to the floor, i'd re-bleed them, make sure the fluid is coming out clean and not dirty, and if its still going to the floor i'd have to make a bet theres air trapped in the MC.

 

I bench bled the mc too

 

Rebleed!

I had mine solid as a rock then crank the car and almost to the floor

go in a criss cross pattern when bleeding

 

So I replaced the booster with a new one, re-bench bled my new mc, checked the vacuum of the booster and air tightness of the hoses going to it. Check valve is on the correct way, brakes are re-bled all the way around, and still, when I start the car I have zero brake pressure! Wtf?! Anyone have any other suggestions?

 

I'm confused on your definition of 'pressure'.

When you have the engine off, do the brakes work (you can stop the car)?

Regardless to whatever this pressure problem is, with the engine running can you stop the car?

Do you have -STOCK- MC and Booster, or have you done some 'upgrade'?

 

Stock mc and booster, engine not running/ or the check valve put on the wrong way and the cars brakes work fine, and the brake pedal feels great. But once the car is on and running(with the check valve placed in the right direction) the brake pedal can be pushed down with no resistance

 

You are talking about the brake pedal which is not helping at all.

Do the brakes work to stop the car or not?

 

The brakes will stop the car with the check valve on the booster the wrong direction. But once its in how it should be the brakes will not stop the car at all. the pedal has no brake pressure

 

You know, that sounds completely impossible to me.
Brakes should work with or without a booster so I have no solution ideas for you.
Sorry =/

 

Did you put the new seal for the master cylinder and lube it with grease?

 

I am having this exact same problem, and on mine, I have replaced both the booster and MC.
I did bench bleed the MC, I'm checking all my lines for leaks now.


I am new here and any help would be appreciated.

 

Go back and bench bleed the master cylinder...

 

did you ever find out what the problem was? I've done the exact same things to get by brakes to work and there no brakes..

 

I had a bad brake booster and MC, as well as a leaking front driver side caliper. Replaced all the parts and blamo! perfect brakes

 

Hi everyone i had the same probleem i just brought new calipers and brake pads but the probleem was on the non-return valve
What you can do is just turn the non-return valve around