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Oct 6, 2011 | 09:53 AM

orange77

Thread Starter

Heel & Toe

Joined: Feb 2006

Posts: 17

Likes: 0

From: Hopkinsville Kentucky

1977 Brakes...

Hi Everyone,

I need a little help. I have an orange 1977 L48 4sp vette with 90k original miles. I haven't had many problems with the car since I bought it, but now I'm having issues with the brakes. It has no pedal. It will stop, but the pedal goes to the floor. I've replaced the master cylinder and it will have pedal for a little while, but will eventually loose it.Now I read an article about having runout in a rotor causing this, but I've also been told that a failing vacuum booster would do this too, so here I am asking for help. Any suggestions?

Thanks,

Stuart

Oct 6, 2011 | 10:00 AM

MelWff

Race Director

Joined: May 2006

Posts: 18,620

Likes: 2,553

A failed booster causes a hard pedal. Did you bench bleed the new master? Did you check all 4 calipers for leaking seals?

Oct 6, 2011 | 06:43 PM

orange77

Thread Starter

Heel & Toe

Joined: Feb 2006

Posts: 17

Likes: 0

From: Hopkinsville Kentucky

Yes, I bench bled the master cylinder and had brakes for most of the summer. Now they won't pump up or hold pressure. I haven't started looking at things. I wanted to ask so I would have a direction to go.

Thanks,

Stuart

Oct 6, 2011 | 06:48 PM

Ganey

Race Director

Joined: Apr 1999

Posts: 11,520

Likes: 13

From: CORVETTE 77 385 C.I. TEXAS

Quote:

Originally Posted by MelWff

Did you check all 4 calipers for leaking seals?

Look at the tires underneath inside for fluid leaks. Some of us are rebuilding the SS calipers w/ VB new design O-Ring pistons.

Oct 6, 2011 | 09:44 PM

KevinK

Drifting

Joined: Jun 2007

Posts: 1,404

Likes: 1

From: Ansonia/NYC CT

You want to check the inside of your wheels for brake fluid. If you don't clean that area of your wheels often, you'll know the brake fluid by the clean streaks going down, lol. Then check the front, feel for slickness on your calipers. If it's there, it means you have bad seals. Also, since you've got your wheels off, and the car up, check the lines, as well. Run your hands over the lines, and feel for that extra slick feeling of brake fluid on your hands. Are you having to FILL the MC? Is there just as much in it as there was when you first installed it? Just to help you get an idea for how much you are looking for. Even one little drop means there is air in the lines. Also, another while you're at it, check those lines for kinks, or anything like that. Those lines are in some pretty vulnerable areas, if you ever hit a bump wrong. If there are no leaks, and the MC is new, and the lines are fine...it might be time to start asking about rotor run out.

Oct 6, 2011 | 09:47 PM

63split63

Burning Brakes

Joined: Mar 2005

Posts: 1,231

Likes: 34

From: Ontario

If you don't find a leak somewhere in the system you probably have a problem with rotor run out.
A wobbly roter will actually pump air into the system causing the symptom you describe.
A leak will allow air to enter as well
Bill

Oct 6, 2011 | 10:11 PM

markids77

Melting Slicks

Joined: Jun 2009

Posts: 2,709

Likes: 3

From: Savannah GA

Get it in the air on stands, and have a friend pump the brake pedal while it's running. Grab each rubber brake line while he/she pumps and see if the lines are blowing up like balloons... they will "give" quite a bit if they're getting ready to burst from old age and can make the pedal travel a long way.

Oct 7, 2011 | 05:45 PM