Welcome to the Corvette Forums at the Corvette Action Center!

Mystery brake problem

NVvetgirl

Member
Joined
Jul 18, 2004
Messages
22
Location
Las vegas
Corvette
75 Stringray
My project car a 75 has been sitting in the garage most of the year. I'm now getting ready to do some work on it and when I pulled it out of the garage the brake pedal went to the floor. I can't pump it up and it still goes all the way to the floor. I check the brake fluid, there is plenty. No leaks of any kind under the car or anywhere I can see. Anyone have any ideas what happened to the brakes?
 

Vette79

Well-known member
Joined
Jan 23, 2007
Messages
1,392
Location
Millersville, MD
Corvette
1979 L-48 Black Coupe
After bleeding my brakes a gazillion times the problem turned out to be the Master Cylinder. I had the same symptoms.
 

jdp6000

Well-known member
Joined
Aug 23, 2004
Messages
646
Location
Aurora, Ontario, Canada
Corvette
1982 CROSSFIRE
My project car a 75 has been sitting in the garage most of the year. I'm now getting ready to do some work on it and when I pulled it out of the garage the brake pedal went to the floor. I can't pump it up and it still goes all the way to the floor. I check the brake fluid, there is plenty. No leaks of any kind under the car or anywhere I can see. Anyone have any ideas what happened to the brakes?


Maybe the master cylinder. Maybe not.

Three other things.

Air or moisture in the system. Bleed the brakes.

Or the check valve in the front of the master cyclinder (should be one way only)is gone. Pull it out and see if you can blow through the inlet side but not the opposite side.

Or the hose going to the block has disconnected or is leaking.

Jim
 
Joined
Jan 1, 2002
Messages
7,246
Location
Washington, Michigan
Corvette
'67 Marina Blue Convertible
Or the check valve in the front of the master cyclinder (should be one way only)is gone. Pull it out and see if you can blow through the inlet side but not the opposite side.

There are no check valves (actually residual pressure valves) in a Corvette disc brake master cylinder; they're only used with drum brakes. :)
 

The73vetteman

Well-known member
Joined
Oct 13, 2003
Messages
339
Location
Michigan
Corvette
'73 L48 4spd
My money is on it being the master cylinder. Brake fluid is hydroscopic (I think that's the word) meaning that it absorbs water from the air. Water in the fluid leads to rust. Rust in the master cylinder (and elsewhere) leads to scored bores and damaged seals.

This is why brake fluid should be replaced every few years. I speak from experience; when I bought my 73 the brake fluid was a nasty chocolate brown color and my first job was to replace the cylinder.

BTW - I know they can be rebuilt but frankly I'm not sure it's worth the effort.

J
 

jdp6000

Well-known member
Joined
Aug 23, 2004
Messages
646
Location
Aurora, Ontario, Canada
Corvette
1982 CROSSFIRE
There are no check valves (actually residual pressure valves) in a Corvette disc brake master cylinder; they're only used with drum brakes. :)


Maybe we are talking about two different things. I have an 1982 and I have 4 wheel disc brakes (did they make vettes with drums?). The hose that goes from the intake to the master cylinder attaches to a plastic male pieces at the front of the master cylinder. This male piece is removable. Vaccum goes one way through it.

See booster check valve below

BoosterCheckValve.jpg
[/IMG]

Jim
 
Joined
Jan 1, 2002
Messages
7,246
Location
Washington, Michigan
Corvette
'67 Marina Blue Convertible
Yup, that's the check valve for vacuum to the power brake booster; not related to the master cylinder.

:beer
 

wishuwerehere82

Well-known member
Joined
Sep 6, 2003
Messages
2,314
Location
Rochester, NY
Corvette
Red '82 Coupe,Sebring Silver '98 Coupe
No pressure and no leaks means you ruptered the O-rings in the master cylinder.
I have replaced several for the same symptoms on several cars.
Some just rot the O-ring until it cracks, and some rust the cylinder and shave the O-ring until it passes fluid by it. Just get a new one and bench bleed it before you put it in, and it will be good as new!
 

Corvette Forums

Not a member of the Corvette Action Center?  Join now!  It's free!

Help support the Corvette Action Center!

Supporting Vendors

Dealers:

MacMulkin Chevrolet - The Second Largest Corvette Dealer in the Country!

Parts/Accessories:

Vetteskins

Advertise with the Corvette Action Center!

Double Your Chances!

Partners

Top Bottom