Brake puzzle

[GAmes]

I have been restoring a glass top '54 Ford for the last (please don't laugh) 15+ years. Total body off with as many OEM, NOS parts as I could find during the assembly. I am within inches of buying insurance and actually putting it on the road. It came from the factory with power brakes, power steering, electric windows and an electric front seat. Finding parts was time consuming and expensive. This is what it looked like when I brought it home. The picture is deceiving, it was a rust festival.

This was September, no wind shield, missing trim.

As it sits now.

So much for the back story, here's my problem, cut and paste from the early Ford forums I belong to.

My car has a factory vacuum brake booster that was recently repaired by White Post Restorations under warranty because it leaked. Great service, no complaints. Yesterday, while checking for a power steering leak the brake lights lit up. I hadn't applied the brake pedal. My immediate suspicion went to the booster but even after I shut off the engine the lights stayed lit. I cracked the bleeder screw and the lights went off. Today I disconnected the vacuum hose and hooked up a gauge. 18 inches at an idle, drops to 15 or 16 when the engine revs and jumps to about 22 when the throttle is released, then back to 18. That seems OK to me. Here is the weird part. With the vacuum hose disconnected during my check the brake lights came on. I jacked one front wheel off the ground and the brakes were, in fact, applied. I waited a few minutes and they went out. I reached into the window and started the engine again without touching anything except the key. In a couple minutes the brake lights illuminated again. Anyone care to take a crack at what would cause the brakes to build pressure while the engine is idling with the vacuum hose disconnected?

I should add, the booster is mounted on the inner fender, not to the MC. I can provide a picture if asked.

 

[Tuesdak]

Yes a picture.

Vacuum eliminated.

Something else may be moving to apply the brakes. Including pinched brake lines or hoses. An internal hose flapper drove me NUTS one time till I found it just before the IP inlet over a lack of engine power. Engine heat and vibration could be moving something. A somewhat informed guess is the pedal isn't returning enough to uncover the return ports in the Master Cylinder and the M/C is heating up enough to apply the brakes from fluid expansion. Second guess is the fender to firewall brake pivot is moving as the fender warms up from engine heat.

What happens when you pump the brake pedal after the lights turn on?

 

[petersonj]

How is the booster energized since it is not mounted to the master cylinder? A picture would help.

- John

 

[GAmes]

If I apply the brakes the brake lights remain on.

As you can see, there isn't any linkage connecting the MC and the booster, only a brake line. You can also see the brake light switch mounted on the aft section of the booster above the outlet brake line. The pedal free play is too high, it's max should be 7/16 and I have over an inch. That is something else to address but I don't think it's relevant to this issue.

 

[GAmes]

How is the booster energized since it is not mounted to the master cylinder? A picture would help.

- John

The description of operation in the FSM is rather lengthy. The short version is that when there is pressure from the MC a gate opens which adds vacuum pressure to the outbound brake line.

 

[Timd32]

If there is a spec for the actual pressures involved maybe you can get a break pressure gauge and measure the various in and outputs.

The brass fittings in the Willys repop world are notorious for quality defects. Same with the banjo bolts.

Maybe you can just look at the ID of the copper washers used or part numbers in original parts breakouts, there is a sequence of ID size washers on Willys and its super easy to get it mixed up.

 

[BigPapa]

Wow, Gary, that’s NICE.

So, basically the brake master cylinder acts like a modern clutch master cylinder that moves a slave cylinder attached to the booster.

 

[petersonj]

It could be as simple as the piston in the master cylinder is not retracting fully, thus trapping fluid downstream. With a small amount of heat added, the trapped brake fluid would expand and begin applying the brakes.

I think the following test would at least isolate which circuit is involved - the master cylinder, or the brake booster:

Duplicate the problem and when you see the brake lights come on, loosen the port on the master cylinder. If the brake lights go out, then I would be looking for a problem with the master cylinder, such as a piston not fully returning. If the brake lights stay on, then it is likely a problem with the booster unit.

Also (not sure about your master cylinder), but back in the days of drum brakes, single master cylinders had a residual check valve in the outlet port. This maintained a few psi in system when the brake pedal wasn't applied. The purpose was to ensure that wheel cylinder cup seals didn't collapse during idle periods. Maybe - just guessing here - there shouldn't be a residual check valve in the master cylinder, but should be one in the outlet of the brake booster hydraulic port. I think it would be worth looking into.

- John

 

[BigUglyRacing]

My daily is working on baby birds (55-57) newest car in the fleet is a 69. I have been through these systems and they are not too hard to rebuild. I remember going through a nos 1960's rebuild from Wagner and came across a reference to the rubber bumper that goes in the in front of the brake pedal rod in the master. It said to remove if using power brakes. Also, pull the master apart and check the spring valve assembly.

Also on the birds the brake pedal rod that enters the master I believe is an eccentric bolt that will adjust freeplay. pm sent

 

[NIsaacs]

Nice car Gary!

I would check the push rod adjustment. It might be slightly too long and is holding the cylinder slightly engaged. Here is a generic picture of a diagram of a vacuum canister. Note the push rod, it is threaded for adjustment, it just don't show the special nut on the end.

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[GAmes]

Thank you all for the input. With the dialog I have received from the Ford forums, and you guys, I think my problem is the MC. The eccentric adjustment bolt on the brake pedal that BigUglyRacing referenced doesn't have nearly enough adjustment to take the excessive free play from the pedal. In other words, I believe the cylinder isn't moving back to it's intended position when the pedal is released.

 

[GAmes]

I'm back. same problem. The brakes do not release and I'm pretty sure the MC is the problem. I replaced all the flexible hoses to eliminate that possibility. I took the MC out, disassembled it, found nothing amiss, and reassembled it. Bench bled and reinstalled. Nothing changed so today I fabbed up a brake line from the MC direct to the brake line manifold which bypassed the vacuum power brake unit. Without bleeding any one of the wheel cylinders I pumped up the brakes and waited. The wheels that are off the ground were locked. I checked the brake pedal again and it was hard at about mid stroke. With air in the lines I expected the pedal to go to the floor. Before I order a new one, did I miss anything?

 

[petersonj]

I pumped up the brakes and waited. The wheels that are off the ground were locked.

It sounds like a master cylinder problem. When you put the master cylinder back together, did you verify that the piston is fully returning, i.e. is the compensating port uncovered?

- John

 

[GAmes]

It sounds like a master cylinder problem. When you put the master cylinder back together, did you verify that the piston is fully returning, i.e. is the compensating port uncovered?

- John

It moved full travel. After posting I went back out and employed the wife to pump the brake pedal. The rear tires lock up with application and release when the pedal is released. However the front stays locked. What is so puzzling is that the pedal remains firm even though none of the bleeders were opened and I know that there is air in the lines.

 

[petersonj]

The rear tires lock up with application and release when the pedal is released. However the front stays locked.

So you are saying that when the pedal is released, the front brakes stay locked, but the rear brakes are free. Is the brake light still on?

Do you have drum brakes all the way around, or disc brakes? Or, a mix?

- John

 

[GAmes]

Brake light turns off. Drum brakes all around. Single reservoir MC. What has me so mystified, besides the firm pedal, is there is a single line to a block. From there it is split to the left wheel, the right wheel and a single line to the rear brakes. I just realized I need to disconnect all the lines to the block and check to make sure there isn't any blockage.

 

[BigUglyRacing]

I am sure it's not the issue . But if the brake shoes or drums are contaminated with grease or fluid they will lock . Your build is too new but something to keep in mind. Also make sure shoes slide smoothly on the backing plates.

 

[petersonj]

From there it is split to the left wheel, the right wheel and a single line to the rear brakes. I just realized I need to disconnect all the lines to the block and check to make sure there isn't any blockage.

You just might find your problem there.

- John

 

[Ozymandias]

Do you have a vacuum assist or hydroboost?

 

[Timd32]

I have a 1957 Chiltons and it goes over many types of power brake units.

This looks like the Midland Hy-Power

They have a pretty simple operation section to share with others.

POWER BRAKES
MIDLAND STEEL
PRODUCTS HY-POWER
BRAKE (REMOTE TYPE)

This system consists of a vacuum
operated booster complete with a slave
hydraulic cylinder which operates the
regular hydraulic brake system, see Fig.
79. This type of system is referred to as
the remote type and is similar in theory
to the 130-R and 130-S models used on
Chrysler and De Soto.

Operation
In operation this unit is known as a
vacuum suspended system in that the
diaphragm is held in the released posi-
tion by a return spring and has vacuum
on both sides of it. Application of the
brakes operates the control valve to
allow atmospheric pressure to enter
the front portion of the vacuum cyl-
inder. With vacuum still maintained
on the rear side of the diaphragm the
air forces the diaphragm to the rear
and the plunger attached to the dia-
phragm applies pressure to the slave
cylinder which builds up the hydraulic
line pressure to operate the brakes.
Should the vacuum fail to be present,
the brakes will still operate. The brake
fluid will by-pass through the slave
cylinder piston openings and the piston
and cup orifices so that the brakes will
be applied directly by the master cyl-
inder.

CHECKING OPERATION
OF THE SYSTEM

Power Unit Operation Test
Having the engine turned off, apply
the brakes several times to eliminate
all vacuum from the system. Now apply
the brakes and while holding the pedal
steady in that position start the engine
The pedal should move away from the
foot or at least require less pressure to
hold it in position. This indicates that
the power system is working

Checking for Leaks
With the engine running, depress the
brake pedal all the way. Hold the peda!
in this position for one minute. Any
downward movement of the pedal dur-
ing this time indicates a brake fluid
leak. Any kickback of the pedal indi-
cates a vacuum leak

Checking Engine Vacuum
Connect a vacuum gage between the
power unit and the check valve. (The
check valve is on the unit.) Run the
engine at idle speed and check the read-
ing on the vacuum gage. The gage
should read between 18 and 21 inches
of vacuum. Stop the engine and note
the rate of vacuum drop. If the vacuum
drops more than one inch in fifteen sec-
onds the check valve is leaking. If the
vacuum did not reach 18 inches or is
unsteady, an engine tune up is needed.

-----------------------------------

They then had 2 simple checks to point in some sort of direction. But these are in the Chrysler DeSoto section for the 130-R and 130-S which the reference in the description of the Midland.

Brakes Will Not Release
Properly

TEST
FOR K-H MODEL 130-R OR
"90" ONLY
With the engine shut off, apply the
brakes
several times and note if they
release. If they do not, crack the line
petween the master cylinder and the
power
unit. If this releases the brakes
the trouble is not in the power unit. It
it does not release the brakes crack the
ine to the wheel cylinders. If this re
eases the brakes the trouble is in the
power unit,

CAUSE
Improper opening of the fluid check
valve at the end of the control piston.

CURE
Remove the primary cylinder end cap
and check for damaged or missing trip
rod stop plate or trip rod.

NON-RELEASE TESTS FOR
BOTH REMOTE TYPES
With engine running, check the
brakes for release. If not released,
crack the line between the master cyl-
inder and the power unit. If this re-
leases the brakes the trouble is not in
the power unit. If this does not release
the brakes, crack the hydraulic line at
the end of the cylinder between the
wheel cylinders and the power unit. If
this releases the brakes, the power unit
is at fault.

CAUSE
Missing inspection screw and gasket

CURE
Install inspection screw and gasket
Note: The inspection screw and gas-
ket are on the main housing cover. This
screw and gasket act as a seal for a
10/32 tap hole used as a vacuum gage
connection at assembly in the factory.

Bleeding Brakes-K-H Models
130-R&S (Remote Type)
With the engine off depress the brake
pedal several times to be sure that all
vacuum in the system has been ex-
hausted before starting to bleed the
brakes.

The K-H Model 130-R or <90 has no
bleed screws

Note that the K-H Model 130-S has
four bleed screws. Start with the one
nearest the vacuum cylinder and work
out to the one on the outlet of the
secondary cylinder. Do one at a time.
After bleeding at the unit the wheel
ylinders can be bled in the normal
manner.

Loss of Brake Fluid from the
System
TESTS FOR BOTH REMOTE TYPES
Check all points for leaks such ag
wheel cylinder cups, master cylinder
cup, line connections, etc. Replace or
tighten any part which leaks.
If this does not cure it, remove the
unit from the brackets and disassemble
the main housing clamp rings and re-
move the housing cover. Examine the
interior of the cylinder for fluid leak-
age. If fluid is found in the vacuum
cylinder, renew cups and seal assembly
and thoroughly examine the cylinder
bore and push rod for scratches in the
finish

Unit Does Not Boost
TESTS FOR BOTH REMOTE TYPES
With vacuum in the unit, the engine
running, listen for a rush of air through
the air cleaner while the brake pedal is
being depressed, using a fairly hard
brake application, If no rush of air is
heard, remove the vacuum source line,
empty unit and run the engine to deter-
mine if the vacuum is being created in
the line by holding a thumb over the
end. If no vacuum is created in the
line, the line is either blocked or re-
stricted or the ball in the vacuum check
valve is stuck.

Note: The vacuum check valve is
either at or near the engine intake
manifold.

If in the first test the rush of air is
heard through the air cleaner while the
pedal is being depressed and yet the
unit does not boost, it will be necessary
to disassemble the unit and check the
fuid check ball and also the diaphragm
for breaks which interfere with its
operation.

Master Cylinder Return Line
Both of the Kelsey-Hayes remote type
units have a line which returns excess
or leaked fluid to the master cylinder.
This line contains a check ball which
will permit the excess fluid to return to
the master cylinder but prevents it from
returning back to the unit itself.
This check ball rarely gets into any
difficulty but if it should it can be re-
moved easily and cleaned and replaced
without completely disassembling the
power unit.

The only time that any test is neces-
sary on this check ball is if there is no
other apparent reason for loss of fluid
in the brake system.