Just follow their instructions on the Motive website and you should be fine.

 

It seems brake bleeding is a popular forum item- that and and vacuum issues. I used several bleeding methods over the years and the most successful for me has been the Motive bleeder. The least successful has been the wife pumping the brakes. Im not saying the brake pedal pumping is a bad method, it just doesn't work with my wife invovled.

 

Doesn't that kind of defeat the whole purpose of working on your car anyway?

 

My brakes are now better than they have ever been. Solid pedal that engages at the very top. Hallelujah! Here are a few observations. When I removed the MC I found it was installed with washers between the MC and the firewall. I had to check the assembly manual to see if this was correct,,, it was not. This moved the MC forward a bit. This made the pedal have to move just a bit farther to start the braking. Inside the bore there are little orifices up into the reservoirs, the seals need to move past these before any brake pressure starts. I removed the washers. My pedal starts braking much earlier than is did before.
I have bench bled the MC before but I found something new, for me. As you push in on the plunger it compresses the first spring and you feel some resistance. I thought this was the end of the stroke. I found that it will press farther in when the second spring compresses. Knowing this will help a lot when bench bleeding. As I pushed farther in I was able to get more air out of the MC. Air bubbles will come out of the hoses, and even more out of the small holes into the reservoirs. After bleeding the MC level, in the vice, I tilted it a bit forward and then backwards. I was able to get even more bubbles out as it was tilted. Two BS wives tails. First I keep hearing not to push the plunger all the way in because it will tear the seals. BS! This is only true in OLD rusty POS MC's, it has nothing to do with a new shinny MC bore. The plunger has a limiting rod and a spring so it doesn't compress to far. Second,,,, keep the MC level when bleeding. Air in the bore will ALWAYS be at the top of the bore. You can never push the seals far enough to zero out the air/fluid space. Just pure physics! When you tilt it just a bit the air will move up against the seals, then when you push to bleed it, the air will find the little holes up and out of the reservoir. Air will never push down and out, only up and out. There are seals pushing forwards and backwards, so tilting it both ways help force the air up and out.
After installing the MC I bled the brakes with my new Motive bleeder. I was surprised I didn't get any air bubbles from any of the bleeders. I used more than a quart of fluid. But my brakes are very solid now.
Just so you can breathe again,,, I rebuilt and reinstalled the "brake light warning switch". Trust me,,,, it isn't a proportioning valve, metering valve, ETC. It's only function is to light up the brake warning light, when the front or back brakes fail. It doesn't shut off any fluid, it doesn't meter anything, it doesn't proportion anything, it's not adjustable. Even with the heavy duty brakes, that were offered in 1968, it was the same. Your 68 could have very easily been modified by "bubba" but that doesn't make it correct. It may be better, but not original. Not that I really care about originality. I see many of these switches for sale. They even call it all sorts of things, but that doesn't make it so either.
Whew!
Two other notes: At some point you have to remove the MC bleeder fittings. If you do it after installing the MC on the car, fluid will leak out and air might seep in. While still on the bench I put the MC cap on and installed the short lines and block onto the MC. Also,, With the MC installed, rear of the car up, the MC checked with a bullet level and tilting front lower, I took the cap off and pushed the pedal in slowly, I got lots of air out of the reservoir holes. This was just after I carefully bench bled it. Not sure why or where the bubbles came from. This technique is documented on YouTube. You can also get a hard pedal.

 

Good to hear you've achieved solid braking.

You're right that that block isn't anything more than a pressure switch. The isolation of the front and rear systems is taken care of in the two-reservoir set up of the master. Earlier Corvettes (I think pre-'67) have a single reservoir serving all 4-wheels so that an isolating block becomes necessary to maintain some level of braking ability if you lose either front or rear pressure.

 

The Motive Power Bleeder is a tool that has brought me great success in fluid replacement and bleeding. I highly recommend adding it to your tool supply.

 

for 1974, you would bleed nearest to m/C? Why not from the furthest?

 

The front and rear are two completely, separate, different, systems, nothing to do with each other. Bleeding front or back first doesn't matter. For that matter, the right and left sides are connected with a T fitting, so it doesn't really matter if you do one side first or not either. But you should do both sides twice in case air does get past the T fitting. Left right left right. The only reason people say to start from the farthest wheel first, is more air comes out sooner if you start at the farther wheel, but either way a small bit of air can still get past the T to the nonbleed side either way you do it, so do both sides twice. Let's hear it.

 

Here is the solution gravity bleed each caliper and use DOT 3 non silicone. I just did one caliper on my 77 and the fluid was gross after 12 oz of fluid it cleared up..I have been doing brakes since the 1970 and it just takes time and i have a M otive bleeder and will use it when i place my replacement caliper on!

 

I also finally got a Motive bleeder. I found this to be the most foolproof method to bleed the calipers.

 

I have a Motive Bleeder as well But the problem is that air wants to go UP not down. This made me switch to pushing the air UP and OUT instead if forcing it downward. Pushing the air up from the calipers works very well for me as long as you have the right tool.

 

If you are using the bleeder screws on the top of the caliper, you are still trying to push air down and out of the caliper with a pressure bleeder hooked to the caliper. If you are bleeding the MC, with pressure from caliper this can work. Bleeding the caliper vs MC is two different issues.