A little help from my friends....

[windrider50]

Ok, I'm thinking I'm so far in to this problem that I can't see the forest for the trees. My 72 coupe sat for about 6 years, and as I awoke it, the brakes had disappeared. Translation: pedal went to floor, no braking at all.

Ok, so I rebuilt all 4 calipers, installing VB&P's O ring conversation kit, 4 new rotors (the old ones appeared to be original), and a new mater cylinder from Corvette Central.

Now the pedal goes almost all the way to the floor, and barely holds the car at idle in forward or reverse. The brake warning lamp is functional, but does not illuminate when I press on the pedal, indicating to me that the proportional valve is not an issue. I have not taken it out on the street, as I feel decent brakes are a good thing!

I have bled those puppies by gravity first, then via the pedal approach until NO bubbles appeared, then I went around and tapped on each caliper with a rubber malet to dislodge any trapped bubbles. Then I bled them again and saw little or no bubbles. No leaks apparent anywhere.

Other than the power poster, any ideas? I thought when the booster goes bad, pedal effort increases, which is not I case I find. I will checking the length on the adjustable rod that transmitts the action from the booster to the M/C vs the spec.

Any and all suggestions ( as they relate to my problem) will be greatly appreaciated.

Thanks

NJ BB Ken

 

[GTR1999]

Check the runout even though you have O ring calipers. See if they are under .005", .003 is better. Bleed the system again. A small pressure bleeder like motive makes works great and is fully independant.

 

[Copdogcorvettes]

Another problem that shows up alot after being in storage or just sitting a few years is the flex lines go bad. They let air pass through and you may not see any leakage. I have had this problem twice over the years. Tried everything I could think of to get brakes and nothing worked; replaced the flex lines and it finally start to make adifference.

This may not be your problem, but it is a place to look.

Gary

 

[Ol Blue]

Windrider50

I had a similar problem when I put all new everything on my 68. I pressure bled them from each brake caliper, over and over, still no pedal. After reading and following the directions I pushed the brake pedal down about an inch and pressure bled them again. That fixed the problem. I believe that pressing down the master cylinder a bit, it opened up and allowed brake fluid in.
Ol Blue

 

[The73vetteman]

Did you bench bleed the new master cylinder? Just a thought.

I just changed my front calipers and rotors (got the VBP O ring ones - can't afford to do all 4 at once!) and it took a lot of bleeding and brake fluid to get all the air out. Make sure you're bleeding in the right sequence - furthest from the cylinder first - and be very careful that no air gets drawn back in.

 

[windrider50]

Last night I decided to check the booster unit, it will not hold a vac. which I beleive means it's NFG. Surprisingly, the engine idles nicer without being attached to a major vac. leak!!


Anyway, I think that this is at least a significant source of my lack of braking, although the brakes make still need additional bleeding.

Anyway, any one out there that has replaced their booster unit have any tips, tricks, condolances?? I hear that it is a bi**h to replace, as the mounting nuts inside are practically un reachable.


NJ BB Ken

 

[tomsgota724spd]

Sounds like your on the right track. With out a pressure bleeder vette brakes are tough to bleed. Rotor runout is not a problem since you have not driven the car. Because the brake pads have not been bedded in,"used yet" they can cause a slightly soft pedal. The booster is not that bad. Just be patiant.
Tom.

 

[Culprit]

Once you get the booster fixed, I'm a huge fan of using a $25 hand held vaccum pump to suck the air/fluid out of the bleeder valves. Cheaper than a pressure bleeder and faster and more effective than gravity. Do this in combination with Speed Bleeders (the bleeder valves with a check valve built in) and it's about a 30 min, 1 person job to bleed the whole car. Changing the flex hoses is always good advice. Good luck.

Semper Fi,
Culprit