Night Hawk

Hi everyone! Can you help with this kinda quickly?

Last night I went out to pickup my girlfriend and I immediately noticed that my brake light was showing up in the dash. Usaully this light shows up everytime I apply the parking brake, so I thought I had it on, but when I checked it wasn't applied. I then thought the emergency brake handle must not be all the way down but it was, I even kinda shook the handle just in case there was a bad connection, but there was no change in the light being displayed.

I then said screw it and proceeded to drive out of my driveway and immediately noticed I had to press the pedal almost to the floor to stop, they were really spongy for some reason. When I got back home I checked the master cylinder to see what the brake fluid level was on. Their was hardly any fluid left in BOTH section of the reservoir! I topped it up and this evening the level was still fine. The weather is damn cold here right now -20. Does brake fluid contract under extreme cold? I don't believe I have a leak, the brakes have never failed me before and the underbody of my car is mint including the brake lines. Two summers ago I had new rear calipers installed. Oh yeah, even after I topped up the fluid, the brake light is still being displayed.

I know I will most likely have to bleed the brakes, but will I also have to remove the master cylinder and perform a bench bleeding of it as well as the four calipers?

Any idea's of what exactly is causing my problems?

TomP

I'll bet you the master cylinder is leaking from the rear seal. Look at the base of the m/c where it goes into the booster, and check for brake fluid (or a trace of any "leak line" on the booster itself).

You can get a rebuilt master cylinder for $35 ($10 core), or you can get the repair kit for $25. You might want to rebuild your own; that way, you know it's done correctly. When you remove the m/c from the car, depress the piston in with a screwdriver, and remove the lock ring that holds the piston in. (Youll have to push the lock ring down with a screwdriver so it swings into the bore, then remove it sideways with pliers). The piston will POP up at you, so be careful. Check the bore for scoring, or anything that might've torn the rear seal. If the bore's messed up, put the m/c back together, and get a rebuilt one.

You have rear discs, right? The A1-Cardone part # for that master cylinder is 10-1997. I don't have the Bendix rebuild kit # handy, but you will have to go to a "real" parts store (not a fancy chain store like Pep Boys/AutoZone, but the "local" ones where you can walk in with a cigarette and nobody complains). You know the kind of stores I mean.

http://www.expressautoparts.com might also carry it.

You might want to look into the Phoenix Injector to bleed the master cylinder; look for my message about rebuilding my rear brakes. That tool is awesome; and saved me a ton of time. From the way your brakes sound, it seems like you've probably dragged (er, pushed) a ton of air thru your brake system, and you're going to need to bleed the WHOLE car after doing the master cylinder. The Phoenix Injector will cut that time into a few hours.

The brake light appears when unequal pressure is felt between the front brake circuit and rear brake circuit. The pressure differential switch is a one-wire switch located on the proportioning valve located right below your master cylinder.

As a side note- the reservoir for your front brakes is the REARMOST master cylinder reservoir, closest to the firewall- the largest one. (It activates "first" when you press the brake pedal.) The rear brakes work off the FRONTMOST (smaller) reservoir. Keep that in mind while you're bleeding your brakes.

Also, since your whole system is basically screwed, now would be a GREAT time to replace all those original brake hoses. There's two in the front, about $25 each. If you have rear drum, there's one in the back (body to axle). If you have rear disc, there's two in the back (body to axle, right caliper to axle line).