# Brakes fine with engine off but soft/bearly work while running...



## tec_rabbit (Sep 14, 2001)

I went through a search but didn't find any solutions so here I go. Just did a VR swap in my 91 and took my booster off to change the mounting bracket and pedal cluster. I put new front calipers and hoses on and the whole system is bled. Brakes are rock hard with out engine running (no vacuum) but when the engine is running the pedal goes right to the floor? I'm thinking something happend to the booster? To all the people who had this problem how did you fix it?


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## Blk95VR6 (Nov 9, 2000)

*Re: Brakes fine with engine off but soft/bearly work while running... (tec_rabbit)*

It may be a bad master cylinder, I'd check that first, you can damage them when bleeding brakes if you have an overzealous foot when "pumping" the pedal to get pressure up. Just my .02...
Mike


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## DemonEater (Jan 29, 2001)

*Re: Brakes fine with engine off but soft/bearly work while running... (Blk95VR6)*

Well, if the pedal is hard with the ignition off, and doesn't sink even with constant firm pressure on it, the master should be fine.
To me, that just sounds like there's still air in there somewhere.
You could disconnect the lines, block off the ports on the master, and see if it still does it - if so, bench-bleed the MC, and try again. If not, the air's in your lines somewhere. Usually when boosters go bad, the pedal gets very heavy, not soft.


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## brilliantyellowg60 (Aug 30, 2001)

*Re: Brakes fine with engine off but soft/bearly work while running... (DemonEater)*

we bled the system with a Motive Pressure bleeder
today he says he lost all brakes








we'll see what it is soon


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## bearing01 (May 27, 2004)

*Re: Brakes fine with engine off but soft/bearly work while running... (brilliantyellowg60)*

How's your vacuum check valve on the outside of the booster? Sounds like a vacuum leak.


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## tec_rabbit (Sep 14, 2001)

*Re: Brakes fine with engine off but soft/bearly work while running... (bearing01)*

Well yes my brakes did fail yesterday but it was a seperate issue...under compression the axle was hitting the brake line and it blew out. Put a new line in last night and re-bled all the way around to no avail. It's not like I don't have brakes when the pedal goes to the floor it's like there is no pressure feedback, it's way to easy to lock the breaks. To much vacuum? I'm going to replace both the master cylinder and the booster just to be safe, I'll put in a new check valve as well.


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## bearing01 (May 27, 2004)

*Re: Brakes fine with engine off but soft/bearly work while running... (tec_rabbit)*

Does your booster do the following:
Stop engine and pump the brakes several times (to depelete booster vacuum). Now, partially press the brake pedal and start the car. Does the pedal go soft and move downward slightly? If so, the booster works properly. But, if you're still not getting any assistance from the booster while braking then it may be that you're not getting enough vacuum. Poor vacuum may be due to the check valve, internal leak in the booster or a collapsed vacuum hose.
Little confusing what you said... "I don't have brakes when the pedal goes to the floor it's like there is no pressure feedback, it's way to easy to lock the breaks". Do you mean the brakes actually lock up the wheels? Because in the first part of the sentence you say you don't have brakes.


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## tec_rabbit (Sep 14, 2001)

*Re: Brakes fine with engine off but soft/bearly work while running... (bearing01)*

Sorry this whole thing is a little difficult to explain..... Yes the brakes will lock up but way to easily. They are sort of like an off/on switch because it takes very little effort to make the pedal go all the way to the floor. I pump them up, hold a foot on the pedal, start the engine and the pedal goes right to the floor quickly.


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## tec_rabbit (Sep 14, 2001)

*Re: Brakes fine with engine off but soft/bearly work while running... (tec_rabbit)*

Well got to the bottomw of things. The actuator rod/adjuster broke inside of the booster and was binding it up. Thanks everyone for the help.


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