A couple times I had to jam on (lock-up) the brakes and all worked good but I noticed the brake light came on and went back off. Good pressure, not to floor and plenty of fluid.

Yesterday the pedal started to drift floorward while holding the brake. Never went all the way down and light never came on. Releasing and reapplying pressure seemed to stop it. Will know better in a bit since I have to drive it shortly.

It's never done this before. Is my power brake unit going or what?

 

i have a 82 gsl and i have had that problem before and my brake light comes on alot...i would also like to know what is happening. but you should be ok though....ive only lost total brake power one time and them it went away for a while.

 

Need a new master cylinder, both of you.

 

a new master cylinder hummm...how hard is it to install. i have a haynes manual for my car. it shows alot....not too hard right?...a days work?

 

.5 hours should be it start to finish. You may NOT need a new master cylindar though... The brake light will come on if your fluid is low... also if your fluid is just high enough to close the circut but when you brake (what you are describing) the fluid moves away from the sensor causing the light to come on.

You may just need to top off your fluid is all. As your brake pads wear the fluid gets lower because the pistion is further away in the caliper/drum. So just check for leaks first... no leaks just top up with DOT 3 or 4 and keep an eye on it.

 

i agree that it sounds like the master cylinder. that would cause the funkiness with the pedal getting soft and such.

 

I agree on the new master cylinder. First check the brake fluid level.

I had the same symptoms on my SE and my Toyota pickup. Replacing the master cylinder fixed the problem for both. Mine wasn't that expensive: ~$40 at Autozone. At that price it is good preventative maintainance if your car has a lot of miles.

The master cylinder is relatively easy. You need to unbolt it from the vacuum booster and then the brake lines. The difficult part is removing the brake line from the bottom of the master cylinder. You will need to bleed the brake lines at the wheel slave cylinders. Remember to to right rear first, Left rear, right front then left front.

Remember to wash the brake fluid off after the repair. Brake fluid is a good paint remover.

 

Get the brake bleeders undone before you start if the car is your only mode of transportation because if a bleeder breaks off, you can't do the master cylinder until you get the broken bleeder out and/or replace the wheel cylinder or caliper. You must bleed all 4 corners to get all the air out. There are somethings you can take shortcuts on, this isn't one of them.

 

Damn good advice Whanrow.....

 

I topped off the fluid and road the pedal to the floor a bunch of times and it finally stopped. had the top of master cylinder off and listed as I did it. Heard a few bubbles but it stopped.

The problem came back the next day. Haven't tried again. And here's a goof.... clutch fluid got used accidently instead of brake fluid. Now what?

 

Clutch fluid? Both the brakes and clutch take either DOT3 or 4.

 

Thank You! I thought the fluids were the same. And whoevere said it about the fluid shifting forward on heavy braking was right on the money. Now I'm going back outside and pump the air out of the thing again and hope it works. Must have sucked some in during my heavu braking and semi-low fluid in the rear part of the master cylinder.