Ocassional Brake Problem

[72Blazerod]

Hi guys,

I finally bought my first Corvette. A 1972 350 auto. It is in really good 'survivor' shape and I am really happy with it. I have only found one problem, the brakes. I have found that when I am driving around the work fine, but when I come to a traffic light and have to sit with my foot on the brake for an extended period of time, the pedal starts to sink until it eventually hits the floor and the "BRAKE" light comes on. The car also wants to 'creep' forward while the brake pedal moves down. Once I start to go again it seems fine. Any ideas?

Rod

 

[Vettehead Mikey]

Master cylinder has an internal leak. Have it rebuilt and keep it if it's the original, or exchange it with a rebuilt if it's not. Even Canadian Tire has them!

 

[wishuwerehere82]

Yes.

I agree. Master cylinder is leaking inside at the O-rings.
Get a new one, and bench bleed it with the fittings provided before you put it in, otherwise you will have to bleed the whole system.

 

[The73vetteman]

Corrosion in the braking system is a big problem on older cars. Like the man said, you probably need a new master cylinder.

Bench bleed it before fitting, but I would also bleed all four wheels. Bleed out a whole load of fluid. It's hygroscopic (I think that's the spelling) meaning it absorbs water. Everyone should change their brake fluid every two years, but no one ever does, and it's the water that causes corrosion and braking problems.

'73

 

[GTR1999]

Sounds like a nice car, I have the same! Like 73 vetteman said old brake fluid will drive you crazy. I would get the car up on jack stands and pull the wheels.
Were the brakes worked on since you got the car? If not check the entire system, don't rely on what the previous owner said he did,unless you know it for a fact. Corvette brakes aren't too hard but they can be costly to repair so most cars I see for sale need brake work.
When the brake light comes on it means there is a pressure differential change in either the front or rear system. You have a divided M/C, the front section is for the front brake calipers, the rear is for the rear. If there is a fluid leak or air in the system you get a pedal like you describe. Look for signs of leaks on the inside of the tires, look in the M/C to see if it is low and what section,look at the fluid it should be clear to very light brown BUT not muddy or dark. The hoses also fail on these cars, they swell internally and close. I saw a 69 coupe that caught on fire from a locked right rear caliper because of a brake hose.
Does your car have SS brake calipers? You might just need a M/C but check everything. Also you must have less then .003" runout in the rotors and .001-.003 bearing end play or you'll have problems with bleeding and maintaining the brake pedal.
Good luck and ask questions.