How close is too close?

[Russ69Runner]

One of those Sunday drivers. Or was on the cell phone.

 

[69hemibeep]

He tried to turn left from a stop sign across 3 lanes but we got in the way

 

[Russ69Runner]

I hope every one was ok. That is the way some of these people drive these day's. When at a stop light when it turns green I always look both way's you just never know.

 

[69hemibeep]

We are ok

 

[Russ69Runner]

Thank goodness for that 69hemibeep. It is amazing what these new car's can take for impact. They are built pretty darn good. I guess with all the crash testing done since the 60's they are far improved on body structure. We use to think the best car for a crash was a big car like a caddie. Or one of the big old's cars. Now these smaller cars just seem to bounce of off thing's. Russ.

 

[taguy16]

Still haven't got this braking problem solved. I still have a brake pedal that goes all the way to the floor with no resistance at all when the car is running. Now I'm thinking the problem lies in the master cylinder since as mentioned earlier it's a reman unit from Carquest. I'm wondering if when the rebuilder cleaned up the piston bore in it it got honed too much and the piston isn't sealing in the bore. What seems to be happening is the piston in the MC doesn't appear to be able to push any brake fluid thru the system under enough pressure to move the wheel cylinders and caliper's pistons. It's got to be this or it wasn't reassembled right (or it never got rebuilt at all).

I can't think of anything else it could be since I don't have any leaks or air in the brake lines and I've adjusted the brake shoes in to where they are starting to rub the brake drums.

 

[Russ69Runner]

So have you checked the power booster to see if it is good or not. Or do you have a vacuum leak. When my power booster went out the pedal would go to the floor board. Just a thought Of other thing's that could be wrong. Russ.

 

[taguy16]

So have you checked the power booster to see if it is good or not. Or do you have a vacuum leak. When my power booster went out the pedal would go to the floor board. Just a thought Of other thing's that could be wrong. Russ.

No-haven't checked that. I'll have to look into it. Thanks for the idea.

 

[Russ69Runner]

Taguy16. I seems like you are doing a good job of finding out problem's and fixing them. I have replaced the diaphragm in several power booster's before. It is tricky but take your time and it will go well. I don't know if your model car's power booster has a rebuild kit for it or not. Russ.

 

[taguy16]

Taguy16. I seems like you are doing a good job of finding out problem's and fixing them. I have replaced the diaphragm in several power booster's before. It is tricky but take your time and it will go well. I don't know if your model car's power booster has a rebuild kit for it or not. Russ.

My car is supposed to have the "Midland" brake booster and there are are rebuild kits available for it, but they are very expensive - about $300 with shipping. I think if the problem does turn out to be the booster then I'm going to see what it takes to convert the car to manual brakes. I don't like power brakes anyway.

 

[Russ69Runner]

You know I am with you on that Manual work's pretty good and you don't lose 10 HP. from the motor. It don't have to pull that vacuum to make the brake booster work. When they go out their is no warning. Just like power steering have throwed belt's on them before and had to struggle to drive the car home. I agree with you these booster's are big and are in the way when working on the motor. I seemed to be in the way when pulling the valve cover off on most cars. Also trying to work on the exhaust manifold. Maybe that is your problem buddy. Hope you find the problem.

 

[taguy16]

So...I plugged the outlets of the master cylinder today to test it, and the brake pedal wouldn't go down at all when I pressed it indicating the MC is okay. What I plan on doing next is capping off all the lines to see if I in fact got all the air bled out of the system, and if so then I know the problem lies in the brake calipers or wheel cylinders. I also decided to replace the drum brake hardware which I never did when I replaced the wheel cylinders and shoes. I may go thru the wheel cylinders again while I'm at it to make sure they are still working as they should: I have a concern that the pistons in them aren't contacting like they should and are stuck since the car has sat for so long without the brakes being used..

 

[Russ69Runner]

Sound's like you have a plan. taguy16 hope you get it worked out.

 

[taguy16]

After capping off the brake lines before they got to the wheels I got a slightly better brake pedal - it didn't go all the way down to the floor - despite not getting one of the caps to seal up properly. I'm thinking then that the problem could be what I originally posited in my thread, that most of it could be because the rotors and drums are so thin. I think it's time to break down and get some new ones, if for no other reason than to rule this out.

I would also like to remove the brake booster because my sense is that isn't helping matters any. Basically I would have to get the parts needed to convert to manual brakes. Does anyone know what all I would need besides a different MC pushrod and MC to prop. valve lines? According to my research in 1973 B (& E) -bodies used a MC with a 1" bore for manual brakes and a MC with a 1 1/32" bore for power brakes, but in '71-72 the latter MC was used for both manual and power brakes. 1/32" isn't much difference between the two anyway so I don't think it would pay to change my MC since I know it works properly from the test I did.

I've never seen a '71-74 B-body or a picture of one that didn't have a big honkin' brake booster bolted to the firewall so I don't even know what the set-up looked like. I'm thinking manual brake cars must have been rarer than power brake ones and were mainly six-cylinder equipped cars. I'll bet you most six-cylinder equipped B & E bodies have either been crushed or turned into V-8 equipped cars.

 

[taguy16]

Found a picture of a beautiful '72 RR with a 400 c.i. and manual drum brakes:.

 

[Cranky]

As the shoes/pads wear down, yes, your pedal will have more travel and your MC will show a lower level. This is why from time to time the level is checked and if low, add some and your brake pedal should come back to a normal height. When I first got my 66 Belvedere, it needed brakes but they still worked well but the rear drums were grooved beyond the maximum but being it had 10x1.5's on it, there were none available at the time even though new shoes were available. Being a machinist, I turned them myself since I knew no one else would.

My plan was to install an 8 3/4 but it was no where near ready for that. Well, the old rear drums ended up being .040 over max size and still had some grooves in them. Geez. This was about 30 years ago and was using the car to drive back and forth to work. After getting it all back together and bled out, I figured it needed a good testing and well, it passed my test. My surprised was that they didn't warp!

Anyways, had a good pedal and the travel was also very good. Just because your rotors and drums are at the end of their useful life doesn't mean you can't get a good firm pedal. There's something else going on. Are your front rotors stock for the car and are the bleeders at the top? I've seen people get the wrong calipers or get the right swapped with the left and the bleeders ended up being lower than at the very top and you can't get all the air out. Also, drum systems need a residual valve to keep a bit of light pressure on the system to keep air from getting in. It keeps about 10 psi on the system. The MC should have it in the port. If it's not there, it doesn't take long for air to find it's way in. https://www.speedwaymotors.com/Speedway-Drum-Brake-Residual-Valve-10-PSI-Purple,7502.html

 

[taguy16]

As the shoes/pads wear down, yes, your pedal will have more travel and your MC will show a lower level. This is why from time to time the level is checked and if low, add some and your brake pedal should come back to a normal height. When I first got my 66 Belvedere, it needed brakes but they still worked well but the rear drums were grooved beyond the maximum but being it had 10x1.5's on it, there were none available at the time even though new shoes were available. Being a machinist, I turned them myself since I knew no one else would.

My plan was to install an 8 3/4 but it was no where near ready for that. Well, the old rear drums ended up being .040 over max size and still had some grooves in them. Geez. This was about 30 years ago and was using the car to drive back and forth to work. After getting it all back together and bled out, I figured it needed a good testing and well, it passed my test. My surprised was that they didn't warp!

Anyways, had a good pedal and the travel was also very good. Just because your rotors and drums are at the end of their useful life doesn't mean you can't get a good firm pedal. There's something else going on. Are your front rotors stock for the car and are the bleeders at the top? I've seen people get the wrong calipers or get the right swapped with the left and the bleeders ended up being lower than at the very top and you can't get all the air out. Also, drum systems need a residual valve to keep a bit of light pressure on the system to keep air from getting in. It keeps about 10 psi on the system. The MC should have it in the port. If it's not there, it doesn't take long for air to find it's way in. https://www.speedwaymotors.com/Speedway-Drum-Brake-Residual-Valve-10-PSI-Purple,7502.html

Yes, the rotors are stock for the car and the calipers are installed correctly with the bleeders up as they have always been. I went ahead and got new rotors and installed them, overhauled the calipers, and bled the front brakes and now I have front brakes, but the pedal still has to be pushed all the way to the floor to activate them, which is only about 6" since the brake pedal sits so low on this car. I installed new drum brake hardware and overhauled the new wheels cylinders I got for the car some time ago in case they had gotten frozen from the DOT-3 brake fluid that I had in the system that I got rid of. It's amazing how much corrosion damage DOT-3 brake fluid causes in just a matter of a year or two: you don't realize this until you start taking apart braking systems that have it in them - I don't think I'll ever use it again!

As far as the brake pedal sitting so low to begin with: the research I've been doing on these cars seems to indicate that that was how Chrysler designed their power brake systems so the driver didn't have to lift his or her right foot up too far after having it on the gas pedal to get to the brake pedal. I still don't think they intended the pedal to have to be pressed down all the way to the floor to slow down or stop the car with the brakes, and I think there is still something fishy going on. When I have all the lines blocked off before they get to the wheels I can't press the brake pedal down at all, so I'm sure the system up to there doesn't have any air in it; however, when I connect the brake lines in front up the pedal goes all the way to the floor to activate the brakes. I still haven't hooked up the rear brakes yet, so I may do this just for grins, but I'm not holding my breath that this will change matters.

I'm at the point now where I'm ready to do something drastic like change the whole system over to manual brakes so I have one less major component to worry about being the problem - the brake booster. Like I mentioned earlier I'm not a big fan of power brakes to begin with and the main reason I kept them was for the sake of originality. From what I've read the '73 and up B-body braking system had such large rotors that you really don't need power brakes to be able to stop the car without a lot of effort. It would be nice if I could find a matched pedal pushrod and master cylinder that I know will work together. Near as I can tell manual brakes didn't use the the complicated pedal linkage power bakes did and just used a pushrod going straight from the pedal arm to the master cylinder.

 

[Ernie]

Don’t see where brake pedal freeplay was discussed. What amount of free play u have?

 

[taguy16]

I either have none or 6" worth of freeplay in the pedal depending on how you look at it.

 

[Russ69Runner]