V8kilr

well thats just about it,
if i hit the brake just once and hold it the engine kinda drops about 200 rpm then picks back up to about 100 rpm below idle.

then if i hit the pedal really fast the engine dies,

so far i have rewired just about everythig under the hood,
and that solved alot of problems,
when i bought the car the guy did say "it has electrical problems"

so now im rewireing the whole back half of my car "from the seats back"

i just cut out every single wire going back there and it still does it,

i was thinking short wire,or bad ground or something,but i guess not,

also yesterday i just reran a ton of wires under the dash,

it now has a nice 10 gauges wire feeding the interior powered up by two 40 amp relays,

i just dont get it,
also my blinkers used to make my voltmeter dip when they would blink but the problem is solved with the new wireing,


so i guess my question really is
how does the master cylinder work?
will this kind of thing happen if it goes bad?
how does it get its power "hence power brakes only work when car is on"
any sugetions?

ben79

I'm not certain what year car you have, or if this changed with different years, but my 79 has a brake booster which draws off the vacuum system. *and* incidentally enough, if it's carbed, the sudden lack of vacuum will make the car stall. So i'm going to take a wild guess. If you have no vacuum leaks from the vacuum lines, the brake booster might be bad, causing your stumbles. Just a thought. i haven't messed with mine for quite some time, and it's 250 miles away from me at the moment. so I make no guarentees

V8kilr

sounds very logical to me,
mainly because me master cylinder is bad,or at least im 99% sure its bad,

is the booster and the master cylinder the same thing?

i have no clue about brake stuff.

ben79

THe booster is the big plastic black cylinder that the master cylinder attatches to. inside the booster is a pushrod which pushes on th MC, but multiple times the force that you apply to the brake. If the booster is shot, it would feel as if you have completely manual brakes, i believe. The technical details of how the booster exerts that pressure through the engine vacuum, however, is not known by me....yet

What are the symptoms which make you think your MC is bad? It could be the booster instead, you might be quite unlucky and it be both

V8kilr

my front brakes do not work at all.

just back brakes,it sucks,

used to leak very slowely,
now it doesnt leak anymore but the front dont work either,


i guess it could be a caliper as well and i just need to bleed them from all the leaking,and when i bleed them it would start leaking again,

also i noticed some brake fluid around the master cylinder once.

tommorow i will bleed and see if i cant find a leak,

also i know the booster is working,when my car is running the brakes are easier to press.

this is a real stumper isnt it,

i thought for sure it was electrical after solving so many problems when i ran new wires.

and i know my last firxt gen didnt do this.

Keaponlaffen

Vacuum booster is behind the master cylinder, and works by the vacuum from the manifold creating a VACUUM (hence the name) on one side of a diaphram (big rubber thing that looks like a plate that flexes easily). The vacuum makes pushing the brake in much easier, and allows you to exert a lot more force on the Master Cylinder than you would be able to if your life depended on it. If you want to see how your brakes would work without the booster, drive to the top of the biggest hill in your city, start down it, get up to speed, and turn off the engine, pump the brakes twice (gets rid of the emergency vacuum) and then try to stop in a hurry... Then proceed to turn the engine back on before you run through the stop light at the bottom of the hill and t-bone someone...

**Beginning of driver's ed** The vacuum booster has a one-way valve in the hose, and allows the left-over vacuum in the chamber to remain after the engine is shut off (and the intake vacuum is stopped), allowing you to have 1-2 emergency brake pumps. So if your engine ever dies on a big hill, push the brake pedal in firmly and smoothly, and then steer to the shoulder without letting off on the brakes... **End of Driver's ed**

Jeff