Brakes go to the floor
 

They stop the car but while im seting at a spot light the ssssllllooowwwlllyyy go to the floor. what should i check.

there is no fluid coming from the master and the fluid is full.

Replace your Master Cylinder with a new one. MC rebuilds are not a good idea.

ok. I also have an oil leak coming from the sending unit? maybe?

Oil leak? You mean MOTOR OIL or brake fluid? And please try to make your statements and questions understandable. Otherwise we won't be able to help you that much, y'know?

yeah its your master cylinder. Get that replaced.

Yeah, as long as you are not losing brake fluid then there is no doubt about it. Replace the MC and you should be set. Check www.rockauto.com for parts...

Before you go replacing your master cylinder (like I did) check that there is no brake fluid coming from your brake calliper. Give the rubber boot a squeeze to be sure.

Well seeing how I posted and got a response then made my own reply saying Ok. then following it with another "question" (kinda i guess) "I ALSO (<-key word) have an oil leak".


But ill retype my ?


I noticed I have a Motor Oil leak, looks like it coming from the oil sending unit (if thats what that is) right beside the drain plug.


ok i will go squeeze the rubber to see if thats the prob now. =)

be gentle

The sending unit with 3 bolts, the larger one, is the low oil sensor, the other is, iirc, for the sub-zero start assist. If it is the 3 bolt unit leaking, re-torques the bolts, gently. If it is the other one, it may need the threads cleaned and wrapped with teflon tape,

just because the pedal went right to the floor doesn't mean that the master cyclinder is busted...had the brakes go like that in my 3/4 tonne and my 1/4 tonne but more times then not its just that the rear lines have burst somewhere...replace the rear brake lines...

If he's not losing fluid, it is a piston seal leak inside the MC. If he were losing fluid, it could be anywhere (but usually the slave). He also has brake pressure, so it's not a burst line. This is a classic piston seal problem.

Another thing to consider is that on the drum brake equipped models, the wheel cylinders can go bad, which is what happened to my '79. More than likely it's your master cylinder though.

Sure...and you'd be losing fluid. The MC the the only place in the system capable of an internal leak.

Oh, I didn't know that. I didn't notice any leaks in my case but then again I didn't look too terribly hard because I switched over to rear discs not long after.

Good to know.

this happend to me, but it could be something very simple called the vaccum hose is leaking on the mc itself. Im saying this because if you take it off and try to use your brakes, they are there, but they are right at the floor, if there is a small leak i could see them slowly going to the floor. If there is no fluid leak in the rear cylinders or piston boots and there is no vaccum leak on the hose then the gasket in the MC is gone.

Chedda, are you sure about that? The brake hydraulic system is a sealed unit. The booster only multiplies the pressure that you apply via the pedal. I believe that if you remove the vacuum line to the booster you will have a very hard pedal, not one that goes to the floor.

Someone please correct me if I'm wrong about this.

Just so there is no misunderstanding, you can have a small leak only under high pressure (hard stops) that may not give you a noticable drop in fluid level over the short term (usually feels "mushy"), but what he is describing is the pedal sinking to the floor -- no matter how slowly it happens, a LOT of fluid is being displaced that must go somewhere. The MC is the only component with seals that can leak internally (around the piston, back to the unpressurized MC reservoir). Every other seal is external. If you have a pressure drop, the fluid is getting around a seal. If the pedal is sinking to the floor, it's a BIG leak. If the fluid is not going down hand over fist, then it's an internal leak in the master cylinder and the fluid is just recycling to the reservoir. Hope that is more clear.

Im damn sure that when you have the vaccum line on there, it will make your pedal harder. Without the hose, it makes it limp like a 80 year old :balls: . Thats what it does on my car anyways, i know that if the valve is installed backwards it will also do the same thing where its soft as hell.

Ya i was thinking that, i was just sharing my experiances.

er - have you checked the brake fluid level? It's also possible that the level is a bit low due to a very slight leak anywhere in the system and has, over time, allowed air into the system to the point where the 'mushy' feel becomes noticeable..

Nevermind...time for bed. :)

Wel to tell you the truth, as of right now i have a small problem. The pedal is "wedding" cock stiff but it takes a tonne of pressure to get anything out of it. How does this fill your hypothesis?

the Fluid is full and has been full since i got the car. just drops verry slowly to the floor, then i can lift my foot off the pedal and press the brakes again and the pressure is back for a sec then slowly goes down every time.

See that sounds like a vaccum leak to me...kinda