no brakes

There is almost always a vacuum brake booster that the master cylinder is attached to.

The question is: What do you mean by pressure being constant? Does the brake pedal sink to the floor slowly? Immediately?

cylinder. or would i have to bleed the brakes to get the pressure to stay constant.

the peddle goes to the floor as soon as u push on it and the brakes barely lock up or apply.

This means either you have a brake line leak or your master cylinder is worn out.

Check the brake fluid level. If it's empty you've found your problem. It's leaking out somewhere.

If you are full on fluid, and the pedal still sinks with no leaking, then it's the master cylinder.

lock up or apply.

lock up or apply.

Or you could have air in the lines and have to bleed them to get air out. john

The only problem with that scenario is... how did the air get in there?

If the problem is truly air in the system, and nobody has opened the system up, then there's some magic happening.

I can't think of a way air can get in to a system, yet no fluid is leaking out. (Unless you have very old moisture laden brake fluid in there that started boiling near the brakes).

I still say leak or master cylinder. But I have to agree with Thomas. If

There is very rarely an instance when a brake system is working fine, then suddenly there's air in the system which needs bled out (with no fluid leaking out). I've never had it happen to me, and I've been pretty hard on brakes that had very old fluid in the system.

============================= There is one way I've seen a few times when there was no other problem. Overheating the crap out of them, boiling the fluid in the front calipers.

Where did the fluid that is no a gas go? What happens when the calipers cool off?

============================= Well I supose it goes up the lines back to the master, I dont know, where else it will go?....All I know is I've seen a few come in that lost the pedal to the floor after a few (or more) panic stops, you can bleed the front and they come back to life. Can't think of any other explaination other than super-heating and boiling fluid.

The gas tends to stay in the calipers. When it returns to a liquid the brakes work as before. But in an event, not something you should be seeing from a few "panic" stops. Something that is not even seen very often on cars coming off mountain runs.

============================== yes, when I said "a few(or more) panic stops" I dont really know how many or the duration of them thats why I said (or more) and originaly "overheating the crap out of them" too. If the fluid should return to a liquid after cooling off, maybe it was contaiminated with something, moisture would be my guess.

Point is unless the operator is racing, like lets say at Martinsville, it just is not going to happen. The fact is this guy is asking about a 1980 car. They don't work because the linings are most likely gone, and the metal lines are most likely rotted and leaking. The Drum hardware is most likely shot the drums most likely over sized due to wear and the rotors real thin for the same reason.

Oh yes, VERY unlikely it is his problem....

ok when i recieved the car it had new brake pads front and rear on both sides. the problem is that there seems to be no vaccum assist when u push the peddle down.plus i can repair it myself rather than paying someone else to do it. i have all the necessary tools and parts at my disposal.

sides. the problem is that there seems to be no vaccum assist when u push the peddle down.plus i can repair it myself rather than paying someone else to do it. i have all the necessary tools and parts at my disposal. ============================ so the pedal doesnt go to the floor, it is just very hard to push?

On 2/05/04 @ 11:41 am You said the pedal goes right to the floor. That is not an assist problem, that is a hydraulic problem.

the problem is that there seems to be no vaccum assist when u push the peddle down.plus i can repair it myself rather than paying someone else to do it. i have all the necessary tools and parts at my disposal.

no straight to the floor

in other words when the peddle hits the floor the car finally decides to stop