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The Anti Yam!
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Discussion Starter #1
Every few years I like to ask this question, mainly because no one has ever answered it.

Does anyone know where the residual valve is on an 80-86 Bronco/F-?50/E-?50?

It's either in the combination valve as part of either the Proportioning Valve or the Metering Valve. Or it is in the Master Cylinder.

This probably hold's true with 79 and earlier trucks also.

87 up trucks have the residual valve as part of the proportioning/bypass valve that screws into the side of the master cylinder.

Why do I ask?
Years ago I gutted my proportioning valve as part of a total brake overhaul and upgraded to T-Bird Calipers, F-350 Master/Booster and wheel cylinders. Now I actually have decent brakes.

But my brakes are very sensitive to how well my rear brakes are adjusted. When adjusted to where my shoes are just barley touching the drums, I have firm responsive pedal from the very top. But this deteriorates after just a few miles of city driving.

After a few miles the top 1/4 of brake pedal stroke has nothing, then at 1/4 pedal they feel firm and responsive. They never get any lower than this.

I know what your thinking, just adjust your brakes... But here is the thing. It did not do this before I did the upgrades, including gutting the proportioning valve. (It always had sucky brakes before, no matter what you adjusted) And if you pump them just once, the second pump will be all the way at the top.

So, does anyone know where the factory residual valve is on this model?
 

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OUT OF BUSINESS / M.I.A.
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We don't have (or need) a Residual Valve. Residual Valves are used in brake systems where the master cylinder is mounted lower than the calipers, typically under the floor. This is a check valve that keeps either 2lb (disc) or 10lb (drum) of pressure in the system to prevent the fluid from running back and overflowing the master cylinder. These valves should be mounted as close as possible to the master before the proportioning valve. These valves are not needed on firewall mounted master cylinders.

Here is the 86-older Combination Valve (no Residual Valve)
 

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The Anti Yam!
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Discussion Starter #5

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We don't have (or need) a Residual Valve. Residual Valves are used in brake systems where the master cylinder is mounted lower than the calipers, typically under the floor. This is a check valve that keeps either 2lb (disc) or 10lb (drum) of pressure in the system to prevent the fluid from running back and overflowing the master cylinder. These valves should be mounted as close as possible to the master before the proportioning valve. These valves are not needed on firewall mounted master cylinders.
Then why do 87 and later Broncos have one at the master cylinder?:whiteflag I was always under the impression that they where used to keep the shoe return springs from pulling the shoes too far away from the drums, which is what it sounds like is happening in Gacknar's case.
 

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My research suggest every vehicle ever produced with self energizing drum brakes had a residual valve.

TSM seems to think it's in the output side of the combination valve.
http://www.tsmmfg.com/Troubleshooting.htm#3

I will, when I go 8-Lug :toothless

Until then, the drums stay.
Then why do 87 and later Broncos have one at the master cylinder?:whiteflag I was always under the impression that they where used to keep the shoe return springs from pulling the shoes too far away from the drums, which is what it sounds like is happening in Gacknar's case.
Yes, you have a residual valve.
AFAIK out put side of combination valve is correct.

Why not buy just buy aftermarket? 10psi runs around $20+.
 

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Then why do 87 and later Broncos have one at the master cylinder?:whiteflag I was always under the impression that they where used to keep the shoe return springs from pulling the shoes too far away from the drums, which is what it sounds like is happening in Gacknar's case.
That is only a Proportioning Valve on the 87-up master cylinders.

Yes, you have a residual valve.
AFAIK out put side of combination valve is correct.
I don’t see one listed in either diagram shown :shrug
Why not buy just buy aftermarket? 10psi runs around $20+.
Tthe aftermarket Residual Valves say theys are not needed on firewall mounted master cylinders.
10psi Residual Valve from Inline Tube
 

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The Anti Yam!
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Discussion Starter #9 (Edited)
Ryan, do a google search on residual valves. All vehicles that came from the factory with drum brakes with a few exceptions had them. I have found articles on Jeeps, Falcons, Mustangs, Rangers, Land Rovers, Nova's, older ford trucks, newer Ford trucks, and even surge brakes on trailers.

But nothing decisive on 80-86 trucks.

And yes, the fluid control valve functions as a residual valve. Our good friend Steve-83 showed that a wile back, but I cant remember where. He did not know where it was on 80-86 trucks, but speculated it was part of the combination valve.

Here is where Shadowfax gutted his for disks.
http://www.fullsizebronco.com/forum/showthread.php?t=196612

I gutted the proportioning valve, but did not touch the output side of the combination valve. If the residual valve is a separate entity in the output side, I think mine is hung open.
 

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Here is the way I always heard the firewall mounted MC explained and why you will need a residual on the drums. FROM HERE

We may as well start with the residual valve, because it is the first one that should be determined whether or not it is needed. This valve does exactly as its name suggests. It keeps a pre-determined amount of residual pressure in the line after you remove your foot from the brake pedal. This aids in preventing excessive pedal travel as well as insuring consistent height to the pedal. In a drum brake, heavy return springs are present to pull the shoes away from the drums. When not in use, the shoes are pulled back until they rest on a centering pin, usually located at the 12:00, or top position, on the backing plate also holding the wheel cylinder. In order to avoid the excessive pedal travel to move enough fluid from the master to activate the shoes, a 10-12 pound residual valve is installed in the line. Sine the return springs are stronger than the 12 pound valve, the shoes are pulled away from the drum in spite of the resistance so no brake drag results.


A disc brake system, however, cannot tolerate this kind of pressure, as it would cause the pad to rub the rotor even when your foot was off the brake pedal. 10-12 pounds of line pressure on a disc brake will cause detrimental drag and a tremendous decrease in pad life. Worse yet, if the vehicle is driven at a consistent speed, the temperature will climb, due to this drag. This will cause the pads, rotors and brake fluid to swell causing lockup. At that point, the only way the brake system will release is for everything to cool back down.


In a stock system, the master cylinder is mounted high on the firewall. The gravity of the fluid in the master will cause 1-2 pounds of natural residual pressure, which is sufficient to maintain constant pedal height in a disc brake. It is for this reason, in most cases, a residual valve is not used with a disc brake. There is one very notable exception. This is when the master cylinder is installed lower than the caliper or drum wheel cylinder. In this case, the fluid would want to return to the master cylinder by flowing downhill like a river. The result would be a low pedal or even no pedal at all! To stop fluid rollback, we would want a 2 pound residual valve, which is just sufficient to stop rollback, but not enough to cause harmful brake application.
To achieve 10 pounds of residual pressure that MC going to be mounted pretty high. As stated before Gacknar's symptoms are indicative of needing a residual valve.

AFAIK it may not be seperately identifiable, and as far as schematics :whiteflag

I just buy new parts with regards to brakes, so I really havent tore into anything like that in a while.

Gacknar,

I plan on doing that upgrade, why do you gut the proportioning valve? I am sure it was in the thread, but alas I do not feel like looking it up.

Maybe Ford decided to call it something else? :whiteflag
 

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yo,
Drum brakes require 6-25 psi be maintained in the brake circuit to keep pressure on the cup
seals. Without this constant pressure, the wheel cylinders will leak. Ford built the residual
check valve into the master cylinder prior to disc brakes. When Ford added front disc brakes, the
residual check valve was removed from the disc brake circuit, but it is still used for the rear drum
brakes. Using a master cylinder on disc brakes that has a residual check valve in the circuit will
cause the front brakes to drag. Selecting the correct master cylinder for your braking system is
critical for safe barking!
by http://www.cometeastcarclub.org/PDFs/BrakePlumbing.pdf


Residual Pressure Valve Location pic in a 93
Source: by Steve83 (Steve, That dirty old truck) at SuperMotors.net


==========

in 96 Workshop Manual
Fluid Control Valve, Brake Master Cylinder
The brake master cylinder fluid control valve (2C161) regulates the hydraulic pressure in the rear brake system. It is located on the brake master cylinder (2140) and is screwed into the rearmost outlet port. When the brake pedal (2455) is applied, the full brake fluid pressure passes through the brake master cylinder fluid control valve to the rear brake system until the valve's split point is reached. Above its split point, the brake master cylinder fluid control valve begins to reduce the hydraulic pressure to the rear brakes, creating a balanced braking condition between the front and rear wheels (1007) to minimize rear wheel lockup during hard braking.

In case of the front brake system malfunction, the brake master cylinder fluid control valve has a bypass feature which allows full hydraulic pressure to the rear brake system.
 

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Roller rockers are gay
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miesk, brings the win! AGAIN! :beer :rockon
 

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Former owner of Shadofax
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Ryan, do a google search on residual valves. All vehicles that came from the factory with drum brakes with a few exceptions had them. I have found articles on Jeeps, Falcons, Mustangs, Rangers, Land Rovers, Nova's, older ford trucks, newer Ford trucks, and even surge brakes on trailers.

But nothing decisive on 80-86 trucks.

And yes, the fluid control valve functions as a residual valve. Our good friend Steve-83 showed that a wile back, but I cant remember where. He did not know where it was on 80-86 trucks, but speculated it was part of the combination valve.

Here is where Shadowfax gutted his for disks.
http://www.fullsizebronco.com/forum/showthread.php?t=196612

I gutted the proportioning valve, but did not touch the output side of the combination valve. If the residual valve is a separate entity in the output side, I think mine is hung open.
I would say this is correct.

When I was researching for that thread link you posted I found a speed site that also mentioned that if you are building a rod, and you mount the MC lower than the brake calipers/drums, then they sell a residual valve for either setup to prevent that leakback into the MC. Otherwise if you're disc with MC mounted in the typical firewall location, no need for residual.
 
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