Bleeding brakes-pedal pressure problem. Could use some advice/suggestions

[Kurt in NJ]

Those “big things” are usually in the end of the bore of single master cylinders.
Most of the dual master cylinders don’t have residual pressure valves — there was a change in the wheel cylinders— instead of just a spring a tapered expander was added to the spring to put pressure on the edges of the cup to keep them in contact with the walls of the cylinder taking over the function of the residual pressure valve.

[glennpm]

They're not big and yes they look like the picture, most 10psi valves are red. Note the end fitting, i.e., not big.
Look at this ebay link.
https://www.ebay.com/sch/i.html?_fro...acat=0&_sop=15


Glenn

[glennpm]

Originally Posted by Kurt in NJ

Those “big things” are usually in the end of the bore of single master cylinders.
Most of the dual master cylinders don’t have residual pressure valves — there was a change in the wheel cylinders— instead of just a spring a tapered expander was added to the spring to put pressure on the edges of the cup to keep them in contact with the walls of the cylinder taking over the function of the residual pressure valve.

The wheel cylinder expander spring coils were not used on the early Fords.
There use and exclusion of a check valve in the master cylinder has in many cases been moved to a brake line manifold, So each arrangement needs to be checked for "Where is Waldo (RCV )"?


This table which I just found on HAMB is a great reference.
https://www.jalopyjournal.com/forum/.../watch-confirm


Glenn

[glennpm]

Ford part of linked table

[Flathead Fever]

Originally Posted by V8 Bob

It really isn't a good idea to pinch shut brake hoses, as unseen damage can occur. The proper way is to plug the line or port with steel/brass fittings.

You are definitely correct. I was an ASE Master brake mechanic. I had mixed feelings about posting that. I only that a few times over 30-years years at work with special pliers with smooth clamps, no teeth, only tightening the clamp by hand just enough to close the hose so it didn't smash it and that that was usually on new hoses. I only did this when I was absolutely having problems getting a pedal to try and figure out where the air was at. We had some big trucks with aftermarket micro locks that locked the wheels up when the truck was parked and in use. They could be absolutely miserable to bleed. The one thing at work is I knew the brakes worked at one time, that all the parts were correct. When you're working on something like you're working on you need to make sure that the master cylinder brake rod is making through its full travel. That the pedal has the correct geometry, that the rod is being pushed all the way in. Once that's determined you can plug off the ports on the master cylinder and see if you have a rock-hard pedal, that way you know the master cylinder is good. You're trying to figure out where the problem is, master cylinder, front brakes, or rear brakes. When everything is correct and adjusted up it should bleed out quicky leaving you with a good brake pedal. I wish I was there to help.

[flatford8]

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I’ve read thru this thread…..post #12 asked if the wheel cylinders had the holes drilled in the correct location…….this has been an issue with after market wheel cylinders……..I didn’t see your answer……post #13 asked what type of brake fluid you are using…..I didn’t see your response…..I’m looking forward, as I’m sure you are, for you to get to the bottom of this……Good Luck…….Mark

[rich b]

Originally Posted by acchaplin

That was a bare, empty MC housing when I had it powder coated. I had metal plugs screwed into the tubing ports. The powder coater taped off the bore and the surface where the lid gasket/bladder seals.

Powder coating is a little more resistant to brake fluid lifting than what paint is.

The inside fitting port looks exactly like Glenn's picture!

Guess I would still be wondering if the 375-400 degree heat affected the residual valves as it sounds like you didn't remove them.


Pedal ratio isn't to bad to figure out. Long side measurement (from pad center to pivot center) divided by short side measurement (pushrod pin center to pivot center) equals the ratio. '40 pedal picture as an example; 12 divided by 1.875 = 6.4 to 1 ratio.

[acchaplin]

GlennPM Sir, 1 great BIG THANK YOU, and 1 regular sized thank you, for your time and research!!

[glennpm]

You’re welcome and I’m glad to help you.

[acchaplin]

I am more confused now than ever over the required (now) use of a brake component I have never had to use, and know nothing about.

I have built 3 other vehicles that have had the MC's mounted BELOW the wheel clyinder level plane. NONE have required any residual valves, pedal ratios or some wild mechanical engineering! Mount the MC in line with the bottom of the pedal, make a rod between the two, bleed, adjust and go have fun! Those three past builds have the same brakes, ('48 car and F-1, F-100 PU) a dual port, front rear MC as this build.

Why, all of a sudden I seem to be in over my head trying to get a simple brake system to work now like it has done successfully in the past?

There is no way those residual valves sticking out of the MC, with 90 degree tubing bends will clear the park brake system, or the drive shaft tube. It's too late into the build to redesign the frame for the MC location. Besides, the entire frame is original holes and all.

The parking brake system is all mounted, chromed, powder coated, working. Cant redesign that.

The rear end is all new (except for axles) inside, and can't change it to open drive.

So I seem to be now stuck between a rock and a hard place,,,,,,,, don't quite know what to do.

[acchaplin]

Originally Posted by flatford8

I’ve read thru this thread…..post #12 asked if the wheel cylinders had the holes drilled in the correct location…….this has been an issue with after market wheel cylinders……..I didn’t see your answer……post #13 asked what type of brake fluid you are using…..I didn’t see your response…..I’m looking forward, as I’m sure you are, for you to get to the bottom of this……Good Luck…….Mark

I posted that the brake fluid I was using. Prestone glycol fresh off the shelf at Advanced.

The bleeders "look" to be at the top of each wheel clyinders. The came from Bob Drake.

[acchaplin]

Originally Posted by Flathead Fever

You are definitely correct. I was an ASE Master brake mechanic. I had mixed feelings about posting that. I only that a few times over 30-years years at work with special pliers with smooth clamps, no teeth, only tightening the clamp by hand just enough to close the hose so it didn't smash it and that that was usually on new hoses. I only did this when I was absolutely having problems getting a pedal to try and figure out where the air was at. We had some big trucks with aftermarket micro locks that locked the wheels up when the truck was parked and in use. They could be absolutely miserable to bleed. The one thing at work is I knew the brakes worked at one time, that all the parts were correct. When you're working on something like you're working on you need to make sure that the master cylinder brake rod is making through its full travel. That the pedal has the correct geometry, that the rod is being pushed all the way in. Once that's determined you can plug off the ports on the master cylinder and see if you have a rock-hard pedal, that way you know the master cylinder is good. You're trying to figure out where the problem is, master cylinder, front brakes, or rear brakes. When everything is correct and adjusted up it should bleed out quicky leaving you with a good brake pedal. I wish I was there to help.

Yeah that is what I seem to need! Someone to stop by that knows what they are doing, that "might see" with the (simple) problem is. Like I posted. This set up has worked in the past. Why all of a sudden now it's not!?

[glennpm]

Originally Posted by acchaplin

There is no way those residual valves sticking out of the MC, with 90 degree tubing bends will clear the park brake system, or the drive shaft tube. It's too late into the build to redesign the frame for the MC location. Besides, the entire frame is original holes and all.

Don't despair, we'll get it fixed.

The first thing you should do today is unscrew the brake lines from the master cylinder. Then poke gently into the center of the MC fittings. If you have RPVs, you'll feel resistance right away. If a paperclip or better, the blunt end of a drill bit slides way in, you have no RPVs.

Regarding the inline RPVs, the red 10psi ones, can be installed in the closest hard lines to the MC like I have done on my '32. There is absolutely NO reason that they have to be screwed directly into the MC ports.

Here is the my rear RPV circled in a blue oval.



.. and here is the one for the front brakes




Also note that you can have RPVs in the MC and also in the rigid brake tubing too. Make sure the flow arrows on the added RPVs are orientated toward the brakes.

Glenn

[acchaplin]

Originally Posted by rich b

Guess I would still be wondering if the 375-400 degree heat affected the residual valves as it sounds like you didn't remove them.


Pedal ratio isn't to bad to figure out. Long side measurement (from pad center to pivot center) divided by short side measurement (pushrod pin center to pivot center) equals the ratio. '40 pedal picture as an example; 12 divided by 1.875 = 6.4 to 1 ratio.

Hey Rich! Guess what!? You were right, stating that the lower brake pedal had been welded and converted.

Very hard to see. Took someone that wasn't hard of hearing in one eye and couldn't piss out of the other eye, to look up in there to see where one of the welds wasn't completely blended in. Normal look up in there that pedal looks "factory"! Somebody did a nice job of converting that pedal.

Ok, measuring with my 6" machinest scale,,,,,,,, I'm partly guessing (because i am not looking straight on) there is 3 and 3/8" from the center of the pedal pivot to the center of the pin that goes through the MC rod clevis, or that hole in the bottom of the pedal. Am I making any sense?

So, if you do your "Jethro Bodine siphern", you know, ought into ought and carry five. What ratio do you come up with in corrlation with a 1" ID MC bore? What do I need, a bigger bore or smaller.? Thanks

[acchaplin]

Hey PM Glenn! Early this afternoon, wifey brought soem "You-Tube" viedos showing "how to mount", "how to adjust", and abunch of other interisting tid-bits up on the TV

The main topic on here of where the residual valves were located, was in the MC. You come along and show pictures of these long looking valves. I am trying to picture how those long S ah B's go into the MC ports! Well, I think that they must screw into the MC ports and the brake line screws into them! All that sticking out from the MC 3" or so.

See, remember, I have NO knowledge of these residual valves, and why this is all a shock to me, since swapping brakes around from the very early '70's!

The one video shows those valves mounted IN LINE on the brake lines! Ah, so THAT is how they go! I understand now! (actual mental relief) They said the 2 psi valves are for disc brakes, and the 10 pounders go for drum brakes.

Another one of those videos said that the smaller MC bore, the more pressure, the bigger the MC bore the more volume. Didn't know that. They used a math formula to figgure of whitch MC bore to the pedal ratio to use. All that math 'siphern is way above my 6 remaining "brane sells." I can do fractions in my head, but that is it.

Another one of those videos, guy was talking about what size and what kind of tubing to use for brake lines. The one guy said that one can't use stainless steel for brake lines, because they are too hard (brittle) to bend or double flair. I bent and double flaired all of mine! A machinest showed me a little trick in the '90's to use when double flairing stainless with a regular tubing flairing tool that has the double flair dies. Oh well.

Now, none of those videos showed EXACTLY where to place those residual valves in corrlation of the MC! Close as possible? Anywhere there is a long enough straight-a-way? Do both valves have to be the same distance from something? MC, wheel cly, first bend?

Then I get on here a little bit ago, and see where you posted your pictures. Wish you would have posted those pictures earlier. I wouldn't have had so much of a shock attack on something i know nothing about.

[acchaplin]

GlennPM. Let me ask yoiu this. Once someone helps me figgure out my pedal ratio, then find the correct size MC bore diameter required for that ratio.

Wouldn't it be easier to get a manual drum/drum MC with that required bore diameter and already have those residual valves in the MC line ports, like in your picture there? Instead of trying to install those in-line valves ( in your pictures) in my existing lines?

In the valve ebay listing you posted, there are several hundred of those valves listed! Boo-coo of those 10 pounders are listed with different part #'s. Confusing to try and figgure which ones will work for me. I think a MC with the correct bore, and the residual valves (which look like they can be removed to powder coat) would be easier and better for me? whaddyatink? Thanks

[glennpm]

Please unscrew the fitting to your MC and see what you have before doing anything else. Ten minute job, well 1/2 hour to gather a drain pan, drill bit and wrench :-)

[rich b]

I would avoid the multiple Chineseum valve listings on eBay and instead get either the USA made residuals from SS Brakes or Wilwood valves from Speedway Motors. We have had good luck with both.

Have had trouble with 1/8 NPT threads in the cheapo valves a couple times; they seem off and tend to want to leak up until the point of the aluminum body cracking.

[glennpm]

Originally Posted by acchaplin

Ok, measuring with my 6" machinest scale,,,,,,,, I'm partly guessing (because i am not looking straight on) there is 3 and 3/8" from the center of the pedal pivot to the center of the pin that goes through the MC rod clevis, or that hole in the bottom of the pedal. Am I making any sense? Thanks

I have a '32 and from the center of the shaft to the pedal mounting bolt is 13"


So for you: 13"/3.375 = 3.85 ratio


(My ratio is 13/3 = 4.33)


Almost all hydraulic converted systems for '32s will have similar ratios since the MC pushrods are below the K member.

[glennpm]

Originally Posted by acchaplin

Now, none of those videos showed EXACTLY where to place those residual valves in corrlation of the MC! Close as possible? Anywhere there is a long enough straight-a-way? Do both valves have to be the same distance from something? MC, wheel cly, first bend?

Then I get on here a little bit ago, and see where you posted your pictures. Wish you would have posted those pictures earlier. I wouldn't have had so much of a shock attack on something i know nothing about.

For the location, the first straight run before any branch , splitting between LF, RF RR or RL brake cylinders. 10psi will then be maintained from the check valve back to the MC. Any other reference regarding just length or bends is wrong for this application.


Sorry I didn't post my pictures earlier. You can see from them how they are located from the MC.