I,m new here so don't know if I am doing all this correctly but here goes. I have a very long throw in my brake pedal on my 76 L-48. The pedal travels almost 3 inches before it hits good hard brake. It stops within about an inch from the floor. In warm weather the brakes are not too bad but in cold weather, not so good. When I first got the car I bled the brakes, had the same situation so bled them again. Still had low pedal. I next installed a new master cylender and while having the old one off measured and adjusted the rod that drives the master cylender from the booster, then bled the brakes. Low pedal still so bled them once more. Yes, low pedal. The last thing I have done is replaced the pads and not normally required to do but bled the brakes. Low and behold, low brake pedal. This is my 9th corvette and I have had no problem of this sort in the past. Can anyone give me a direction on which way to go next? I,m wondering about the booster itself. Can it do this? What about the fluid? Can it give me this problem? Should I "bleed the brakes" Any help is greatly appriciated.

MNodine
In Okla

 

Does the booster need bench bled possibly? My 76 did a littlwe of this but it was because I was pumping brake fluid out the claipers onto the back of the wheels. Once it was bled everything was ok. I read some info on bleeding the booster if the fluid in the master cylinder got too low. Maybe you could look into this?

 

my 76 also did this.funny story actually. Calipers leaked...replaced them. still had problem. Figued master cylinder, so replaced that. Eventually found a pinhole leak in a line. Replaced that. Was better, but...anyway...to make a long story short, the whole brake system was shot. Every time a fixed a problem, it found a new weak spot, and busted through. I would inspect your lines from front to back. It is possible your valve might be contributing to this problem as well. Just my guess.

 

I would assume, since you swapped the pads, you'd know if your calipers were leaking...the plastic on the back of the pad would be wrinkled from the brake fluid...this is similar to my problem, need to replace front calipers in the spring....ummmm...no sign of fluid under the car on the floor anywheres? are you loosing fluid from the M/C wells at all?...even a little? Sounds like air in the lines, but man, you've done a lot of bleeding...are you using a plastic tube connected to the bleeder with the tube into a mayo jar filled with about an inch of fluid during bleeding? And,,,you are aware you have an inner and outer bleeder on the rear caliper on a 76...If all else fails...check ALL of the lines...my 2 cents

 

Thanks people. I have check fluid level all along and have no fluid lose. I have bled both valves on each caliper and used two methods of bleeding, the good old two person system and then later invested in a brake bleeding vacume tool. I bench bled the master cylender before installing and of course the booster will not have fluid in it, if so I "would" be in trouble. The brakes, once the pedal has reached hard brake pedal, is not mushy but indeed a hard pedal. Just the fact that I have so much travel in my pedal and it is so close to the floor is the thing that is not right. I,m afraid that if I had to really stand on it I would hit floorboard. Keep the suggestions comming, surely someone has had this problem.

 

Calipers can leak, and cause such a small fluid loss that it is not readily apparent at the master ...

That notwithstanding though, I suspect your low pedal is from runout in the rotors. Rotor runout moves the pistons on the calipers in and out while driving, foaming the fluid.

 

I am certainly no brake expert, but have completely redone my brakes on my 76. Bleeding was an ordeal to get all the air out of the system, seems like there is a couple places where air likes to hold on.
One thought on the booster would be to try to feel the difference with the car running when pushing on the pedal vs when the car is off when pushing on the pedal. You should feel a difference if the booster is working.

 

If your pedal is "hard" when you get brakes,that could be the booster....My problem(cold) was pedal would go almost to floor,then pump up and after vette was warmed up(driving) pedal was ok...but always problem when cold..master cylinder fixed mine...
Try testing your booster...procedure is in Chiltons Corvette Repair Manual...Section 9....sounds like you are not getting enough assist....if you need procedure,I'll post it,but I can't scan...

 

Got it..try this to check your booster...worth a shot...



Rich

 

Had the same problem with mine, it wasn't till I removed my back brake calipers to replace them that I found the problem. It turned out that my brake pads worn unevenly, in kind of a sloped shape 3/8" on top and .001 on bottom. When you look at them from the top pads look good, but you have to disassemble to know for sure.

 

Brown '76 Vettes ROCK!

 

Yes sir-re bob, this is very true I found out the hard way. Matter of fact I hadda do the rear spindle bearings shortly there after. Do the gripping the wheel at different positions detail and check for any movement. A little bit is O.K. excessive is not. Peace,,, Moosie