Davidmij - Disc Brake Conversion & Rim Problems

[davidmij]

Thx Jon, As poorly as my motor runs I may end up doing that until I get time and money to build the motor. I dropped it off at my mechanic an hour ago - he thinks it may be some adjustment you can make on the proportioning valve. I told him I thought this one was not adjustable, but he said if you pull the electrical connector there's a winding or something in there. Anyway, he's checking it out.

[simplyconnected]

...he said if you pull the electrical connector there's a winding or something in there...

If you unscrew the electrical connector (it's plastic) there is nothing but a spool that slides back and forth.

If the spool is centered, no connection is made. This is normal. If the spool slides to either end, the spool GROUNDS the electrical connection, completing the path for the fault light. There are no electrical adjustments or windings in a combination proportioning valve. - Dave

[davidmij]

Yup, that's exactly what he told me afterwards Dave. He said the install, the lines, the vacuum (at 13.5) the pressure at each wheel, etc are all good. He said the manifold is clear and drawing vacuum well. The only thing left to check is the booster and MC. He thinks it doesn't have enough Throw. So there goes another $90 thanks to this POS from ABS powerbrakes. I guess I'll have to box it up again and send it back one more time.
Oh well.

[simplyconnected]

...The only thing left to check is the booster and MC. He thinks it doesn't have enough Throw...

Looks like we're back to post #11:

Yes, it sounds good so far. You have vacuum, you used the larger reservoir for your front lines, you connected the prop valve according to the diagram, and your booster holds a vacuum even after your engine stops (so you still have power brakes in an emergency).

Run some tests:

With the engine off, disconnect the top pin. Does the booster return all the way to the 'at rest' position (or is the linkage pulling it in)?

Have someone step on the pedal with the engine running, and WATCH the linkage. Does it bind? Does it hit the end of its stroke before the brakes lock up?

If it all looks good, the next part I would look at is the space between your booster and your M/C. (This isn't your brake pedal rod... that's another thing.) How much gap is there? You can measure this without disconnecting lines. If you need to, use a piece of clay or plumber's putty because everything is hidden...

Hey David, did you take any pictures???

These 'checks' are not technical or difficult, but they do take twenty minutes and require a 'helper' foot on the pedal. I believe if you had done them from the beginning, you probably would have found your culprit (and saved yourself a lot of aggravation). I've been here before, but I never bought ABS components. - Dave

[davidmij]

Hey Dave, what do you mean by, "If it all looks good, the next part I would look at is the space between your booster and your M/C"?
The M/C is flush against the booster, it mounts to it.

[simplyconnected]

I know now that you bought the brake combination as an assembly. Since it doesn't work properly, perform the tests as mentioned below:

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

Perform these simple tests. Your mechanic confirmed you have a 'stroke' problem but he may not know how to adjust it properly. You just may have a system that works with proper adjustment. I would hate to see you send back a working unit. I doubt if ABS would refund your shipping costs for the second time.

If you are more comfortable having a mechanic do this work, print out this thread for him. - Dave

[davidmij]

Well, the unit comes assembled and ready to install just as the pictures I posted show. There are three pins. One on the rod that comes out of the M/C and booster. Another below it where it hinges to go through the firewall to the brake pedal rod, and a pivot point just below that. The brake pedal rod has threads and a locking nut to adjust and set it for travel. All of these are pretty easy to see, adjusted and set, so I think I have an OK understanding of how they work. If I disconnect the top pin it swings long and free. If I press the plunger into the booster by hand it squirts brake fluid like a high powered squirt gun.
My mechanic checked all this and the pressure at each wheel. If I open things up I'm afraid these yahoo's at ABS will say I messed with it. I talked to them today and I'm sending it back again.
Time for a beer - I'm depressed.
thx for the help all, Dave J

[Astrowing]

David,

The spacer may be causing the booster rod (link) to not have enough length to give you as much motion as you need. Adding bolts or washers will change the dimensions.

When the brake pedal is in the max up position, the rod in the booster must return completely in the direction toward the firewall. I think without a brake pedal return spring, you're going to rely on the wheel springs to return the hydraulic system back to the neutral state (brakes off).

Conversely, when the brake pedal is in the max up position, the rod in the booster cannot be partially moved in the direction of the master cylinder. There has to be a very small amount of brake pedal motion before it moves the brake link to ensure this is the case.

The brake pedal link is the only link that is adjustable as I understand, therefore any spacers added would need to be between the firewall and the pin where the brake link connects to the center link. This has to be the case for the brackets and links to work in the manner in which they were designed.

Would a diagram help?

[davidmij]

Thx Jim, No need for a diagram, I understand what you are saying. The spacer (adapter bracket) is just right and works the way it was designed to work. Everything returns to the correct place, and there is a slight bit of pedal slop at the top resting position. I also added a spring since these pictures. see: https://picasaweb.google.com/1014928...CK6Gg9yhpdfGWg
It has to be something in the length of the throw or something with the booster isn't at full strength.
- Dave J

[davidmij]

OK, update time on my power, front disc brake job. If you remember, the only thing left to check was my new MC/ booster. I had already shipped it back to the vendor for a replacement because it had a bad diaphragm - they repaired that. I re-installed it but it still didn’t add any power boost. I took the car to my mechanic and he verified everything was installed and adjusted correctly. He said the only thing he can figure is that it doesn’t have enough throw??? However he didn't have enough time to take it all apart as I only paid him for one hour. He said I have a clear and clean manifold with plenty of vacuum (13.5 at 7000 ft altitude). Pressure at all 4 wheels, and no kinks or binds anywhere. So, I sent it back again to the vendor - this time they sent me a different unit. They didn't say if they found a problem or not. Well crap - it's still acting the same as before - no power, and I can't make the car skid no matter how hard I hit the pedal. Without any fluid in the thing I press the brake and it has travel all the way to the floor - I can feel the different points where it feels like the piston is engaging. Once I added fluid and went through the bleeding process it had a regular feel to the pedal. About a 1/4 inch of play at the top and the pedal only travels about half way to the floor at bottom out. (just no power).
I'm lost - should I fork out money to buy a vacuum assist of some kind? Could it be the proportioning valve even though it doesn't have any adjustments? It's the same one Dave Dare posted a diagram of. I guess I'll call the manufacturer again tomorrow and ask if they have any suggestions. Maybe I need to break it all down as Dave Dare described in page 7 of this thread, but I would think they would ship it ready to go.
thx, Dave J.

[davidmij]

Well, I talked to the guys at ABSpowerbrakes. They said the one I sent back tested good, but they sent me another one just for my peace of mind. He also said it doesn't need any adjustments etc for the pedal and/or throw. We talked for a bit and all he could come up with was that my vacuum wasn't strong enough.
Can anyone give me some ideas how to increase my vacuum?

thx, Dave

[Astrowing]

Suggestion:

A vacuum reserve canister captures an extra shot of vacuum from your engine for your power brakes. It is for cars equipped with big cams and power brakes. This unit approximately doubles the volume of vacuum available for your power brakes. It is recommended for cars with 14 inches of vacuum or less. The COMP CamsŪ Vacuum Canisters is made of spun aluminum, which eliminates the hazard of flaking rust particles contaminating the brake system and provides a 50% weight savings over the heavy steel cans of the past.

I think all modern cars have an extra canister in addition to the brake booster. I assume you are not using the original vacuum reservoir, but are running engine vacuum directly to the booster via a check valve.

There are other vacuum canisters out there, I just found Comp Cams when I first looked.

[davidmij]

Thx for the idea Jim, I had already googled the subject and found what you said here so I reinstalled my original vacuum canister but it didn't do any better. If I turn off the engine, wait 20 minutes, and pull the hose off the booster I get a louder, longer whoosh sound so I know it's sealed well and helping. I called the local Ford dealer service center and they said 13.5 pounds at this altitude is about average. I've been thinking that maybe I could have a bad proportioning valve? I was thinking of removing it and installing the original splitter, and somehow plug the rear line off the M/C and see if I get any better power on the front discs??? In case the proportioning valve is restricting flow. Is that even feasible? Would I have to drain the fluid from the rear reservoir so it just compresses the air?

thx, Dave

[davidmij]

Oh, i forgot to ask, are the original brake lines 3/16th inch?
- Dave

[simplyconnected]

davidmij, I can't believe this has gone over 100 posts over the same exact problem. Astrowing, myself, and others, have tried to help you but we are limited to our computers at home and your willingness to try our suggestions.

I am very happy you paid a Certified Mechanic for one hour. That guy actually saw your system first hand, and I examined everything you reported that he said. Then, instead of working with his findings, you sent the second unit back, and here we are back at post #11 with the original problem.

...If you remember, the only thing left to check was my new MC/ booster.

You reported something about, feeling each stage as you depressed the pedal. That should NOT happen. These tolerances should never be that sloppy.This is a 'measurement check' between the booster and the M/C pushrod. It does NOT require booster disassembly at all. What did you find?

...I took the car to my mechanic and he verified everything was installed and adjusted correctly. He said the only thing he can figure is that it doesn’t have enough throw??? However he didn't have enough time to take it all apart as I only paid him for one hour. He said I have a clear and clean manifold with plenty of vacuum (13.5 at 7000 ft altitude). Pressure at all 4 wheels...

Ok:
'Not enough throw,' (you have my suggestion)
'clear and clean vacuum.' (I never thought this was an issue, but you did)
'pressure at all four wheels.' How much brake line psi did he gauge?

...it's still acting the same as before - no power, and I can't make the car skid no matter how hard I hit the pedal.

Yes, this is what you're working on. Your system is exactly like any modern disk/drum setup and should be easy to troubleshoot.

...Could it be the proportioning valve even though it doesn't have any adjustments? It's the same one Dave Dare posted a diagram of... ...Maybe I need to break it all down as Dave Dare described in page 7 of this thread, but I would think they would ship it ready to go...

I have learned, never take anything for granted. That's why I do my own troubleshooting.

You bought your proportioning valve from ABS. If it is the same as a Ford disk/drum prop valve, all the front ports are open to each other with NO restriction. That part works just like a tee. The rear brakes section tames down the pressure to your rear shoes. A common sign of a broken prop valve is when the back wheels lock up before the fronts come in. This is NOT your issue.

I have never seen your new prop valve, so I cannot verify the holes or machining. You can take it off and blow into the front end to see if all three ports are open to each other. Your problem does NOT sound like the prop valve is bad because you should still be able to lock up your front wheels.

Yes, your original brake line was one 3/16" tube that came from the M/C to a tee, which fed all four wheels... standard on all classic drum brake systems. Your new M/C has two 3/16" lines which offers twice the flow... standard on all dual M/C disk/drum systems, but modern cars use the equiv. metric standard.

Adding more vacuum tank never boosts your vacuum, but it offers more volume. That is like connecting two 8-volt batteries in parallel... they still produce 8-volts. Your new booster has enough volume to brake about three times with the engine off. Adding more 'can' allows you to brake about five times (at the same foot pressure) with the engine off.

I have helped you purchase the Scarebird brackets, offered my troubleshooting suggestions, and given as much info as I can. With that, I am done with this thread. Other Squarebird members successfully use the ABS setup (for years) so we know it works well. - Dave Dare