Rodger, I have braided stainless steel hoses so I can't pinch them off. The brakes are 100% perfect while driving the car, pedal height at the top, barely have to touch the pedal to feel the brakes grabbing, stops on a dime. The only problem now is when I start the car the pedal is about 1/2" from the floor and feels as there is no power assist. I am now leaning toward a vacuum problem with the booster internally. I'll keep digging.

 

When you first start up and the pedal is 1/2" from the floor, are the brakes fully applied?
When this happens, try using the other foot on the accelerator and see if the car will move easily while the pedal is so low.

 

Noonie, When I first get in the car with the engine off I have about half of a pedal or a little more. When I start the engine and push the pedal it goes to 1/2" from the floor and the brakes are applied and will hold the car when I put it in gear but the pedal is hard even though it is 1/2" off the floor and I have to put a lot of pressure on the pedal to keep the car from moving. As soon as I drive the car 100 to 200 feet and apply the brakes the pedal is close to the top and stops with light pedal pressure just like a new car. It sorta sounds like a booster problem or low vacuum but the new vacuum canister did not change anything and if it was the booster the pedal should not go down close to the floor before driving. Keep digging!!!

 

That doesn't sound right.
Just for fun, I would put a couple hundred local miles on the car and see what happens to the pedal.

 

Yeah, nothing sounds right about this whole brake problem, but we ARE making progress. I think I'm going to borrow my friends mighty vac, fabricate a way to hook it to the booster, pull a vacuum on it and see how long it takes for the vacuum to leak down. Any ideas on how long a good booster should hold its vacuum?

 

Billy,
I know this is an apples and oranges comparison, but I was doing some "vestigatin" yesterday AM. Car is a 2011 Subaru, almost new, but it has a booster and M/C pretty up front and easy to see. When I got in the car I hit the brake pedal and heard the hiss of escaping vacuum, X2, then hard pedal maybe 1/2" down, car off. Car had been sitting at least 12 hours. I remember getting the same with my '07 Dodge Dakota pre hurricane + tree = trade in.
If you are loosing vacuum, or not building it sounds like a leak somewhere.
Your half pedal, car off does not sound right either. Should be closer to the top once the vacuum is bled off.

 

A long time , hours ,maybe overnight. Are you sure your booster to brake pedal rod is not too tight ?

 

No, the rod is not to tight. Brakes don't drag after driving for 20+ miles and there is a little slack in the pedal while driving before the brakes start to grab when you depress the pedal. I still think its something to do with vacuum. I'll try the mighty vac test on the booster this week and see what the results are. My new vacuum canister loses vacuum quickly after shutting engine off. The gauge on the canister reads 20 " when running and quickly drops to 0 when I shut the engine off. The hoses go from carb to canister check valve then from canister to booster check valve. So somewhere there must be a leak in those components.

 

The reason I ask is ,if the pedal is too tight it will bleed vacuum,just like a leak.

 

I didn't know that. Good information !!!

 

holy crap.... im scared to even begin digging into my brakes but it's the first thing I have to do while putting the whole thing back together from new paint.

Hope you get this solved once and for all.

SUlly

 

My buddy came over and brought his mighty vac so we hooked it to the check valve in the booster and pulled about 12 inchs of vacuum. It dropped about an inch over about 10 minutes but held steady at 11 inchs for a long time while we were doing other stuff. That tells me that the booster is holding the vacuum and not leaking. The new vacuum canister was another story, I could rev the engine and get 22 inchs of vacuum but as soon as I shut the engine off it went to zero. After checking for leaks everywhere we replaced the check valve with one that goes in a booster and that solved that problem. It holds the shut off vacuum for hours with out leaking down. Summit is sending a replacement chrome check valve tomorrow. Now back to the brakes. After fixing the vacuum problem this week end, I started the engine this morning and without touching the brake pedal, I revved the engine a few times to build vacuum in the canister and booster, backed the car out of the shop and applied the brakes. Guess what !! Woopie!!! For the first time since this ordeal started I had good pedal and brakes backing out and for the rest of the day. It seems that the last part of this puzzle has been solved. For whatever reason I didn't have enough vacuum at initial start up to have any power assist when I first backed the car out of the shop.I guess maybe my radical cam wasn't allowing the booster to quickly build enough vacuum at start up and a few seconds of idle. However, everyone has always said that low vacuum or a bad booster would result in a hard pedal and the pedal would be as HIGH as it was with the engine off so that was the way that I was looking at the situation. My brakes were reacting differently, the pedal at start up was 1/2" from the floor, NOT HIGH, but it was hard. Like everything else about my ordeal this doesn"t make sense but alas I think this is as good as it's going to get. The brakes work great, car stops as well as my new car. I just have to remember that I need vacuum and the cannister. The three bad chrome masters were most of the problem. I got brakes after the master the shop owner bought and the canister solved the last bit. Thanks for every ones imput in this thread.

 

On my 69 I changed and flushed the fluid when I got the car 3 years ago. Brakes were working before opening lines but couldn't get anything through system after refill with conventional bleed method and was certain the MC had failed.

What I found thanks to some help from a fellow owner was that you cannot use the conventional brake bleeding method very effectively. I bought one of the hand pump vacuum pumps, me and a friend finally were able to get fluid flowing again to all brakes.
this is the one I have.
http://www.autozone.com/autozone/acc...ier=70116_0_0_
I now own a $69 harbor freight vacuum pump after both of us had hand cramps for weeks. Good news is the brakes are still great after 3 years.

Method is:
Make sure master cylinder is full. The order or bleeding is critical -fartherest to closest to MC.
Proceedure
Close all bleeders.
Go to right rear wheel,
1. attach vacuum pump to bleeder,
2. open bleeder and pump forever until you have clean new fluid.
3. with vacuum applied and fluid flowing close bleeder.

Follow above procedure in this order > left rear > right front > then left front.
Once this is complete you should have some good pedal, use the conventional method in the same order to bleed any additional air from system. You should have a good solid pedal at this point.

Hope this helps, it worked for me.

Good Luck!
Kenneth