Davidmij - Disc Brake Conversion & Rim Problems

[davidmij]

There are no adjustments on my proportioning valve Rusty. It just has an input for front and back. Then one line out for the back brakes and two out for the front. (One for each side of the front)
Let me ask a novice question that just occurred to me. I had to reverse the 8 inches of brake line that goes from the M/C to the proportioning valve, I had them backwards. After that I have air in that portion of the tubing. I never re-bleed that air. Is that enough to make the brakes as bad as they are? From what I remember as a kid air made the pedal just go more to the floor but they would still work half decent. Either way, I best bleed that air out. Sorry I'm such a novice gents, you guys must feel like the mechanic talking to a blond.

[jopizz]

The best way to test the booster is to pump the brakes with the engine off and then hold it down firmly. Then start the car. If the booster and vacuum system is working correctly the pedal should move slightly toward the floor. You definitely should have the check valve in place between the intake and booster. To tell if it's in the correct direction with the valve connected to the intake and off the booster you should be able to blow into it but not suck through it.

[davidmij]

New news!
I just got off the phone with a guy at abs power brakes (they make the M/C setup) He said that the air in the line will just cause the pedal to go to the floor - I kind of knew that. He also said that if I hold the brake down while running the engine, and turn off the engine, I should feel the pedal drop towards the floor - I know exactly what he means, I'm sure you guys do to. That isn't happening if I remember correctly, the pedal is staying real constant whether the motor is on or off. He said that means that one of the two diaphragms is ruptured and I need to send the unit back. I first explained how I feel vacuum, and how the power booster lets the air out after I press the pedal with the engine off. He then said that i will probably feel the engine flutter a little when I press the brake pedal. I'll double check these two little tests tonight and see what I find.

[simplyconnected]

...I don't understand what you mean by the "top pin"...

Your new firewall bracket has three pins; one for the brake pedal rod, one for the bottom of the bracket, and one for the booster clevis.

Whenever something mechanical doesn't work correctly, we disconnect at different points and test for known values.

You assembled the firewall bracket by pulling pins out for the pedal rod and for the booster rod. Wait a minute, I assume YOU did the work...

If you pull the top pin out of the firewall/booster bracket and work the mechanicals by hand, you should discover what it is actually doing.

1) I am going for stroke first; the center links (in the bracket) needs to naturally retract all the way. (nearly touching the firewall.)

2) Pressing the pedal to the floor, the center links should advance toward the booster. How far does it go? Take some pictures.

If you are running out of stroke, the center link will bottom out before the booster can push the M/C spool all the way. Both actions will feel like a HARD PEDAL.

A good understanding of these mechanical actions and ratios is essential in setting up the booster and brake pedal.

You also assembled the M/C to the booster. My question concerns the space between the new booster rod and the new M/C cone (or spool). I asked you to use clay to measure the gap. After you do the first two tests, go on to this one: Pull the M/C off (two nuts), stick some clay on the booster rod, then put the M/C back. Don't touch the brake pedal. Pull the M/C back off again, and measure the clay. This will show the gap between the M/C and the booster rod. Most are adjustable at the booster AND some master cylinders come with a spacer. Remember, the M/C spool must fully retract with no brake pedal pressure.

There is no such thing as, 'bolt it together and it'll work'. At the cost of repeating myself, a good understanding of these mechanical actions is essential in setting up the M/C, booster and brake pedal. I don't know what assembly instructions came with your booster combo and I don't know what components you have. OID sells a Corvette-type of M/C with BOTH reservoirs being the same size. Yours is apparently different, but I haven't seen the pictures. Each component combination needs to be adjusted correctly for proper operation.
- Dave

[davidmij]

Thx John, that's exactly what the guys at "ABS power brakes" (the company that made the setup) said to do. I think we all know the feeling in the pedal that he (and you) are referring to. Here's what I posted on the other link;
New news!
I just got off the phone with a guy at abs power brakes (they make the M/C setup) He said that air in the brake line will just cause the pedal to go to the floor - I kind of knew that. He also said that if I hold the brake down while running the engine, and turn off the engine, I should feel the pedal drop towards the floor - I know exactly what he means, I'm sure you guys do to. That isn't happening if I remember correctly, the pedal is staying real constant whether the motor is on or off. He said that means that one of the two diaphragms is ruptured and I need to send the unit back. I first explained how I feel vacuum, and how the power booster lets the air out after I press the pedal with the engine off. He then said that i will probably feel the engine flutter a little when I press the brake pedal. I'll double check these two little tests tonight and see what I find.

[davidmij]

Hey Dave, none of this makes sense to me, did you look at the picture from the link on my first post? The M/C and booster are made specifically for a 1959 or 1960 T-bird. It came assembled, no pins on the bracket, just a bracket to attach it to the firewall with the original bolts, and to raise the booster and cylinder above the engine valve covers. The brake pedal push rod was already attached to this unit I bought and just has a hinge that raises it up to line up with the cylinder. My car is a 1959. It only had a tiny little single master cylinder in the engine compartment and a K/H booster under the dash.
You are exactly correct when you say that I need to provide pictures if I need help. I've done a horrible job of explaining what my setup is. I'll take some pix tonight and post the link to where you can view them. I don't seem to be able to post pictures to these threads. Sorry for all the confusion, I really do appreciate your help.
thx, Dave

[RustyNCa]

There are no adjustments on my proportioning valve Rusty. It just has an input for front and back. Then one line out for the back brakes and two out for the front. (One for each side of the front)
Let me ask a novice question that just occurred to me. I had to reverse the 8 inches of brake line that goes from the M/C to the proportioning valve, I had them backwards. After that I have air in that portion of the tubing. I never re-bleed that air. Is that enough to make the brakes as bad as they are? From what I remember as a kid air made the pedal just go more to the floor but they would still work half decent. Either way, I best bleed that air out. Sorry I'm such a novice gents, you guys must feel like the mechanic talking to a blond.

Any air in the line is a bad thing. The air compresses more than the fluid which will make your brakes weak and mushy.

Anytime you crack open the lines you need to re-bleed them. Not sure how you are doing that, but I always just run a clear line from the bleed screw down to a jug with some brake fluid in it and bleed away till I see there are no longer bubbles.

Here is what my valve looks like, you probably don't need the adjustability in the valve, but it was a nice feature for me. I know the prop. valve in my olds and the 65 tbird aren't adjustable, but they are both factory....

Cheers and good luck
RustyNCA

[jopizz]

It can only be one of three things; misadjusted brake pedal linkage, bad booster or vacuum leak. Hopefully it is the booster although I'm sure it's a hassle to remove it and send it back.

[simplyconnected]

First things first...

... I don't seem to be able to post pictures to these threads...

Go to the HELP DESK and read about 'How to Post Pictures':
http://www.squarebirds.org/vbulletin...4264#post54264.

You are a paid member which gives you the ability to post your pictures.

Make sure your pictures are not too big. If they conform to the size limits, under each "Reply to Thread" there is a button that reads, "Manage Attachments". Click on it and upload your pictures from your hard drive. You can put a few in each post. Depending on your camera, take your shots as close as possible but still in focus. If you still have problems, send the full size picture to me:
simplyconnected@aol.com

We are here to help, so get those pictures up. I would like to see what's really going on. From your description, I don't sense any broken or ruptured diaphragms. It's possible, but I would hope ABS wouldn't send one out untested. Turn around time and shipping costs are too prohibitive. - Dave

[RustyNCa]

It can only be one of three things; misadjusted brake pedal linkage, bad booster or vacuum leak. Hopefully it is the booster although I'm sure it's a hassle to remove it and send it back.

Personally from what he has said, it sounds to me like his booster is bad.

Sounds like he has gotten the vacuum lines hooked up right now.

It's not to bad to pull the booster on these old birds, lots of room in there to unbolt the master and drop it out of the way. Just don't disconnect the brake lines, eh, there shouldn't be any need to.

Cheers
RustyNCA

[YellowRose]

davidmij - Disc Brake Conversion & Rim Problems

It is important that we do not get a thread off subject. If you are talking about tires or rims in a thread, please don't start talking about another subject, such as converting to disc brakes or working on your brakes. It makes it difficult to locate subjects in a search if subjects are mixed up in threads.

Since the two threads that David started have information regarding tires or rims intermingled with information regarding problems with a disc conversion, I have done this. I have taken the two threads of David's and merged them into one calling it "davidmij - Disc Brake Conversion & Rim Problems." In the future, anyone looking for information on swapping out their rims and doing the disc brake conversion can do a search on "Disc Brake Conversion & Rim Problems" and should be able to find this information.

Please keep your threads and posts on subject when you post. That includes me too!

[davidmij]

Thx Ray, and everybody else. I'll try to be more organized with my posts and threads.
My pictures are here on Picasaweb; https://picasaweb.google.com/1014928...K6Gg9yhpdfGWg#
I pumped the brake pedal and held it, then started the engine. the pedal didn't move at all. It should drop a little as the vacuum builds. The guy at abs power brakes told me this means I have (one) bad diaphragm. I told him I can hear the air rush out of the booster after turning off the engine and then pressing the pedal - he said that means the other diaphragm is good. He also said that if I press the brake pedal (while the engine is running) and it causes the RPM to drop or sputter, then this just reassures that the suspect diaphragm is likely to be bad. (And that's exactly what happens) He said not to worry, the parts are warranted for a year. Guess I'll be pulling it apart and sending it back. What a bummer, everything went together so well and I was really looking forward to taking a spin.
regards, Dave J

[Dakota Boy]

I've learned with these old cars that they will let you drive them when THEY feel like it. Not whenever the **** YOU feel like it.




"Simple jobs" turn into weeks-long teeth-gnashers, etc etc.

[davidmij]

Did my brake pedal look familiar Greg? One day I'll add the clutch pedal.
;~) One day.

[davidmij]

Can anyone tell me how many inches of vacuum I should read on a 352 engine? I'm going to borrow a gauge from Autozone and check it today before I pull my M/C booster setup and ship it back.
thx, Dave