KenMathisHD

howdy! I've got a 94 LT1 automatic. The other day I was driving through an HEB parking lot and went to stop the car and the brake pedal went quite a ways down before I finally felt any resistance. I turned the car off, the pedal felt normal, checked through the lines I could get to and didn't see any leakage. Turned it on and it did the same thing, pedal traveled almost to the floor with no resistance until it got pretty far down there. Turned it off and started going through my Haynes manual (always keep it in the hatch now), call my mechanic, and about 10-15 minutes later I start it up again to take it by an Auto parts store so I'd be where I'd need to be for any tools I'd need, and the pedal was fine, but the brake light kept coming on when I would stop. Get there, turn it off, go in, talk and look around, turn it on and it's fine, not even a brake light. Fluid was about 1/4 inch from the top so I topped it off, but other than that I'm not sure what happened, it drove home fine. I'm hoping it was a one time quirk and not some early warning that the master cylinder is gonna fail, but I doubt my luck will hold. Any thoughts?

antfarmer2

It only takes one time. Sounds like your master is bleeding by the seals. Pump up your brakes while off then hold the pedal and start the pedal should drop just a bit. This will tell if it is a booster or a vacuum problem.

billschroeder5842

You are getting "warned" by your system, so you need to do some quick tests.

I'd do a full on brake inspection and bleed the brakes. You may have gotten some air trapped in the system which would account for the intermittent squishy feel.

Also, get your car up in the air and test the brakes by spinning the wheel and stepping on the brake- they should lock up immediately. This should test your calipers

Check your vacuum lines to the master cylinder. You would not be the first guy to have a bad hose which causes your power assist to get wonky.

KenMathisHD

Pumped the brakes while off and the pedal did go down a bit when I turned it on. As for the vacuum lines, I can't find any going to the master cylinder, though admittedly I'm not 100% certain what I'm looking at is the master cylinder. It's right there connected to the reservoir, yes? Couldn't get it in the air to check the calipers but I don't see any leaking or streak marks down the inside of the wheels. Once I can get her up, I'll check out the calipers, ditto for bleeding the brakes. I'd use the scissor jacks I have but I don't trust them without jack stands.

Patsgarage

The vacuum line goes to the booster , not the MC. Look for a thick rubber hose that goes into a plastic fitting (check valve) at about 10 o'clock on the booster. If you do decide to bleed the brakes remember that these cars do not use the usual RR, LR, RF, LF sequence.

John A. Marker

with antfarmer2. Your seals in the master cylinder are giving out.

VikingTrad3r

im with the boys.

as u step on the pedal the plunger is allowing fluid past it.

fix asap.

KenMathisHD

Is there a way to replace the seals directly, or do I need to replace the whole master cylinder? Also, any recommendations for a greenhorn for bleeding the brakes? The Haynes will say how to do it but I figure it's a good idea to see what do's and dont's and opinions y'all have
And thanks!

1800Wing

After reading these posts it sounds to me like this might be a little more than you want to get involved with. Not trying to be a smartass or make you feel dopey, but if you have to go to an auto parts store for tools you might need and have only scissor jacks...well. Put the car on a rollback and have somebody with the right equipment do it. Can't cut corners on brakes or hope for the best because the brakes worked fine 5 minutes ago. Sorry to be negative but you don't want to end up stuffed under the back of a semi, or blow through an intersection and hit a bus full of Nuns...

later, tiny

KenMathisHD

XD bus of nuns
I had to stop by the auto parts store cause when the brakes started getting funky I was about an hour from home, and I haven't yet gotten a second tool bag for the vette. The scissor jacks though, never gone out and bought a jack or stands cause I've always been able to borrow them. They're on my wishlist though

VikingTrad3r

youtube for bleed lessons. BUT BE SURE you get it right. not hard. i use a hand vacuum bleed kit.

flare wrench set for brake lines off ms.

not a hard job. but obviously not one you want to mess with half a$$ right.

ghoastrider1

time for new pads too if they look thin.

rfn026

My first inclination is to tell you to take the car to a good shop. You've got an old car. Brake issues have a way of escalating. The seals in your calipers are the same age as the ones in your master cylinder. Think about that.

Everyone really needs to flush the brake system every two years. Clean fluid will prevent a lot of problems.

Richard Newton
Car Tech Stuff

ghoastrider1

Hey, how come your home on the computer? You should be out racing making us proud. lol.

KenMathisHD

got a chance to lift 'er up today, went along the lines and couldn't find any leaks, no streaks around them or on the wheels either. Checked the calipers too, wheels stopped immediately and pads are about half worn, though rear rotors could use some attention soon, and vacuum lines to the booster are a-ok, no cracks, chafing or abnormalities, they actually look fairly new. I found a wire who's connection is fairly questionable that connects to the bottom of the master, wire is exposed and pretty frayed. Didn't see it last time cause it's right on the bottom, but wondering if it's part of the problem. Anyone know what it's purpose is? Single little wire into a pigtail on the bottom of the master. Didn't take a pic earlier but will tomorrow when there's good light.
Also, found a master cylinder on Partsgeek.com for a decent price, wondering if any of y'all have words to say about using them for the part

Patsgarage

The plug is for the brake system light on the info center.

A Peter C4

What is the proper bleed procedure? what wheel should be done first,second,third last? I plan to do a fluid flush soon, don't want any trouble with ABS or cause a brake problem.

AirForceOne!

Had the same problem with my 90, needed a new master cylinder and this hard to find brake pressure switch, which the new master cylinders do not come with! I finally found one in Florida! Link below.

https://corvetteparts.com/item/switc...0-1994#details

Wildride

C-4 Master cylinders have been known to experience sudden catastrophic failure. It has happen to me and others. Check out this link and be sure to read Jan800vette's comments and his post crash comments of what caused the failure. (worn seals in the master cylinder).

Scary business.

KenMathisHD

Where's the link...?