I posted a week or so ago about bleeding the brakes on my 75 and I got a lot of good information so I thought I'd post a bit of a follow up. First a bit of backstory. I sandblasted, disassembled, rebuilt, and had the cars original calipers a gorgeous cherry red. When I tried to bleed them after putting them back on the car the rubber boots blew out and the calipers failed (better in the garage than the road, but I wasn't happy). I then learned that rebuilding the calipers isn't the easiest thing to do due to how tight their tolerances are so I cored the gorgeous red calipers for a pair of remanned from Autozone. I refused to put bare iron on my fresh restored front end so I sprayed them with VHT caliper red. When I put the calipers back on I bled them I had no blowout but they leak BAD from the lower half joint between the two halves. This is when I posted about bleeding the brakes.

I'll be going home this weekend and getting another new pair of calipers from Autozone. I'm not going to paint these with the notion I'll put a set of Wilwood calipers on the car in a few years when I'm out of school and can afford it. I plan on vacuum bleeding this set as well as the rears, in the past I've always just used the pedal method and bench bled the MC but it hasn't worked on this car. I'm going to rebleed the MC and then get to work on the calipers.

Now, last night I was reading a post from 2009 here and the gentlemen mentioned the proportioning valve. As far as I can tell the proportioning valve is supposed to cut off fluid flow to a "leaking" caliper or one that's being bled. Doing so would trip the brake light inside the car. I am not getting this brake light.

SO here's my question(s). Is a bad proportioning valve possibly contributing to my soft pedal? (It's not really soft, it goes to the floor, although it will stop the car eventually so I am getting some sort of pressure) If the proportioning valve IS bad can my brakes operate normally? Any advice is greatly appreciated.

 

Very slim chance you have a bad proportioning valve. They are very rudimentary and seldom fail.
If your car is eating up calipers, I would suspect your rotors are out of round. Put a dial gauge on them and check. If you have more than .004 run out that is the problem. In motion, they will pump the pistons in and out at high speed. This causes the seal failure. Remove the rotors and have them resurfaced. I know Autozone recently switched from Cardone to BBB Industries as the supplier for their reman calipers. I have spoken with Eric, the company owner, several times. Very nice and helpful guy. Their product is very good and I'm running them on both my Corvettes.
This should be an easy fix for you.
Greg

 

I had a 75 best brakes on a car i ever had. The secret is place some one in your car and have them hold the brake to the floor, as you open the bleed screw, then tightned the bleed screw until you see clear fluid ,then the person in the car takes foot off brake pedal. Repeat starting at the farthest wheel which is passengers rear when begining. Have clear jelly jar with hose in it at bleed screw and in jar submersed in clean fluid.and if you can use a clear glass jar. So to repeat myself Pump brake in car, hold pedal to floor while you open bleed screw in jar with fluid. repeat until hard pedal. Note master cylinder cover should be off and fluid should never go below one half of master cylinder depth. Also new fluid do not shake or stir or you will introduce air into master cylinder . That proportal valve very rarely goes bad! As far as calipers i use to rebuild mine in thirty minutes but if the walls of your pisto. n are scored you can hone out if they are not to bad other wise look for rebuilt Delco Morandes at Auto Zone. A good measure to is to change front rubber brake hoses because the insides from the toxic brake fluid eats them inside out sometimes as you step on brakes the wheel will pull left or right thats your indication of bad hoses.

 

All: I guess I should have been a bit more specific. The car is in the middle of a restoration and has not been driven with the except of a short trip around the neighborhood after the engine startup after rebuild. The rotors are also brand new and have no runout issues.

Roger on the proportioning valve. I will start the bleeding process over again starting with master cyclinder, right rear inner, outer, left rear inner, outer front right, front left. And report back on if the vacuum method works better.

 

The BRAKE light in the dash serves two functions:
With the key ON pull up on the parking brake handle, the light should go ON.
Push the handle down and the light should go OFF.

At the valve remove the BROWN wire and touch it to a ground, again the light should go ON.
If not then there could be a break in that wire.

 

Pump break pedal, crack bleeder method has always worked for me also.

 

Willwood like most rotor manufactures will instruct you to check their new rotors for run out prior to installation and use.
Just because they are new does not mean they are within spec.
If you did not have them checked you really should.

 

I got home this weekend an fixed the brake issue I was having. To those who seem concerned I checked the runout of the rotors prior to installing them on the car a few months back.

I pulled my master cylinder, bled it, plugged it, and tested it. All good. Re-installed.

I pulled both front calipers and put new ones on (for the third time ) and that seemed to fix the issue after bleeding. Thank you all for your help!