More brake issues...

[02x72]

I finally got the brakes working good on the truck about a month ago, drove it cross country and haven't had any problems. Now Ive got one. About half the time I go to use the brakes, the pedal will go almost all the way down, and then get very firm, at which point the brakes start to catch, but its nowhere near good enough. When it does this, I can hear a vacuum leak inside the cab. Sometimes it will do this, sometimes not. Everything in the brake system is new except the wheel cylinders which looked ok last I saw them, maybe leaking slightly(its on my list), and the booster. Any help?

 

[OLDBULL8]

Fix the vacuum leak. Probably at the your Heater/A/C control since you can hear it inside the cab.

 

[02x72]

There's no vacuum lines running inside the cab. The leak is coming from the booster, where is comes through he fire wall and connects to the pedal push rod. It sounds like a rush of air escaping

 

[FordGuy100]

After the bad braking, if you try to brake again, how does it do? Black truck was similar, it was the brake booster. Got one brake, then you had nothing.

 

[Diesel_brad]

The leak is coming from the booster,

You answered your own queston

 

[CurtIDI94turbo]

Everything in the brake system is new except the wheel cylinders which looked ok last I saw them, maybe leaking slightly(its on my list), and the booster.


Was your Master Cylinder leaking before you replaced it or could your new one be leaking now, and is your brake fluid level staying consistent? I have ran into them leaking internally into the booster and in turn taking the seals out in it. I would suggest pop your vacuum hose and look for trace amounts of brake fluid in it. Also, did you flush your brake lines to remove any contaminants

 

[Cincinnati Guy]

Also wouldnt hurt to check to make sure your rear shoes are adjusted properly.

 

[02x72]

After the bad braking, if you try to brake again, how does it do? Black truck was similar, it was the brake booster. Got one brake, then you had nothing.

Its 50/50. Sometimes it will continue to brake badly, sometimes it will then work perfectly. I just want to make sure that this can be the problem, because the way that whole thing is set up in the truck its a real PITA so replace the booster. So how does a braking system act when a booster is going out/gone is basically what I'm asking. Like I said Ive never had to deal with a bad booster before and to be honest don't fully understand how they work. The fluid level is staying constant in the MC, and the rear drums are adjusted properly. I dont know if the old MC was leaking before, I never drove the donor truck long enough to have it be an issue.

 

[CurtIDI94turbo]

I see you may have a highly modified version of a Ford pickup. Lets start from the beginning again. Everything is new except the wheel cylinders and booster, are we dealing with the rear wheel cylinders and, this is a vacuum booster not a Hydro-boost system?

When you replaced the various parts on the braking system did you flush the entire system, rear included? Contaminates may be in your system slowing taking out your Master Cylinder causing internal leakage between the front and rear sections of the reservoirs. When you push the brake pedal, the MC may be bleeding back in on its self and not building pressure causing extended pedal travel. The vacuum in the booster (the hissing sound) now compensates for this by rapidly building more vacuum. Look for dirt discolored fluid in the reservoir on the Master Cylinder, if its plastic shine a flash light from the under side. If the MC is still under warranty try exchanging it for another, if not pick up a rebuild kit (normally inexpensive) for it and go through it.
Flush, Flush, Flush, the lines, cylinders, and calipers to the system. A power flusher works best for this if you have access to one if not a rubber tipped blow nozzle to blow compressed air through the lines. If all else fails grab a friend who’s bored, (MAKE SURE TO LEAVE THE OLD MC ON) and start draining it one cylinder at a time starting with the one that is furthest from the MC (normally passenger side rear) while they pump the pedal for you. Do this just like your bleeding air out of the system. This will take awhile as when you think your done do it again, dirt and particulates will travel back and forth in the line as the pedal is worked. When you collect the old brake fluid, you can run it through a coffee filter to clean it up to continue flushing the lines. KEEP IT CLEAN LOOK FOR WATER AND ANY THING EALSE THAT LOOKS OFF. IF IN DOUBT DO NOT REUSE IT TO FLUSH. When you install the new or rebuilt MC run fresh fluid through your system one more time using new not filtered fluid. I’m including a link that may help you to understand better how a booster and components work at the end of this. Hope this helps.

http://en.wikipedia.org/wiki/Hydraulic_brake

 

[CurtIDI94turbo]

Forgot something, when you click on the link scroll down to POWER BRAKES this covers more of the booster and its workings.

 

[02x72]

No, its not hydro-boost and it is the rear wheel cylinders I'm talking about. In addition to all the lines being new, they were flushed multiple times when I was trying to fix a previous issues(MC wouldn't bleed). I have a few bottles of brake fluid so I'll flush the system again and see what happens. Thanks for the help and the link

 

[Diesel_brad]

Are the parts NEW or rebuilt? Big difference

 

[02x72]

They're new. I've been down that road

 

[gatorman21218]

have you replaced all the rubber brake lines? They can swell up causing a squishy feeling. They also can act as a check valve, causing the brakes to stick

 

[02x72]

No actually, I forgot about those when I wrote that. Theres only 2 on the front( thats how it should be right? None on the rears). I just went to look at them and they look fine. Would swelling though cause an issue like this, especially with it coming and going like it is?