yellovette

I need some comments here. I replaced the brake rotors, calipers, pads, proportioning valve, master cylinder, brake lines and fluid on my 79', (in short, everything). I then had a shop power bleed the system.

The brake pedal still travels about two inches before it feels solid. Is this normal. I've been told that bleeding the system is difficult on the C-3s. The car seems to brake OK.

What do you think?

GTR1999

Vette brakes are not hard to fix but you must understand the system.
First did you bench bleed the M/C? Sounds like you still have air in the system.
Next you have to be sure the rotor runout is under .005" under.003" is better. Do a search here because there has been 5 years of brake questions here-all covering your problems. If you don't get anywhere let me know and I'll spend more time with you on it.
Gary

Gator81

I don't think so. After replacing all 4 calipers on my '81 and doing a complete flushing of the system with fresh fluid using a Mity-Vac to bleed it at all 4 corners, I immediately had rock solid brakes. I'm sure there's a little travel in the pedal, but it ain't much. Just follow the sequence laid out in the service manual. Trying to remember... seems like they tell you to start with the wheel farthest from the master cylinder - right rear, then left rear, then right front, then left front. I may have that all screwed up... But I do recall that there is a sequence.... The only major thing you've got going that I didn't have is a new master. That makes me suspect air still in it.
Good luck!

mayberg

I bet you're used to driving Fords, right? Welcome to spongy GM brake systems.

Larry B.

Maybe the shop didn't realize that the rear calipers have two bleeder screws and the halve are not interconnected like the front. Omitting the extra bleeders will cause the system to always feel spongey.

Buffalo Dude

I think procedure for bleeding is shortest to longest for vettes, I forget why.

Also, they don't go out very often, but the booster may be bad. I know a lot of people here will tell you otherwise, but mine wouldn't stop even though I replaced everything else. Once I replaced the booster, it locks up all four.

yellovette

OK thanks for those replies. I'll try and cover some of your points;
1) As far as runout on the rotors, I put new rotors on, so that should not be a problem.

2) I did bench bleed the new master cylinder. I think I got all the air out of that.

3) As far as the bleed process goes, the shop that did it, is a Vette shop. Figured they would know about all the bleed points and have done it right.

4) The brake booster was not changed. It's definitely working to power the brakes. Could it still be worn enough to cause excessive pedal travel???????

68raggtop

One thing to consider... the master for power brakes and manual are not the same. Is it possible you were given a manual master cylinder? If my memory is right, the hole in the piston for the pushrod is much deeper on the manual brake masters.

yellovette

Wow! Could be I got a non-power brake master cylinder. Don't know how I'd be able to tell now.

Buffalo Dude

Before I replaced mine, I would press and nothing would happen. It's not supposed to happen, but even when I bottomed out the pedal, the car would hardly stop. There's supposed to be a mechanical backup so that if the vacuum fails, you should be able to still stand on the brakes and stop the car. On a >25 year old car, it's certainly something to consider if all else fails. You don't even have to crack the brake lines, just have to crawl under the dash.

As far as bore size on your mc, I don't think there's a way to check without at least moving it away from the booster, I don't think you need to crack the lines. I'll try to find something on how to tell which one is which.

Turbo-Jet

you MUST check this. do not assume new rotors go on square. the hub/spindle faces were not controlled datums and the factory riveted the rotors in place before final machining.

GTR1999

The last new rotor I used was out .009"

wcsinx

I'm not doubting your experience, B.D., but something just isn't adding up here. With the pedal in any given position, a specific amount of hydraulic pressure is being applied. That pressure will not change regardless of if you have vacuum assist or not. What will change is the level of effort required to get the pedal to that position. All the booster does is suck the pushrod towards the MC and nothing more.

Anyhow an easy test for a booster is to just pump up the brakes with the engine off, then hold the pedal down while you crank up the engine. If the pedal drops once she's running, then your booster is fine.

TJefferson2020

It's easy to tell the difference - this happened to me. A vendor sent the wrong part. Just remove the two nuts holding it onto the booster and separate it just enough to see the back of it. If it's a manual one it will have quite a hole in it where the rod goes in. If it's a power one it will have just a dimple.

Hope that helps.

pm

yellovette

Thanks PM, I'll definitely have a look at that. Also I'll probably try BD's suggestion, ( which I've seen discussed on other threads) to put on a new brake booster. I know it doesn't make a lot of sense but several others have experienced the same problems as me and corrected same by changing the booster. I've never taken one apart but I'm thinking that maybe there's more space than we think between the booster rod and the brake pedal rod.

yellovette