Adjusting new 39 brake system
 

I’m ready to bleed adjust my brakes on the 36. I have pretty much a 39 system with a early mustang drum/drum M/C.
Everything is backed off at the shoes and the lines are all dry.
I was planning on adjusting the brakes before bleeding the system as per the instructions below. My theory was I didn’t want to push the pistons too far out before the brakes where adjusted.
Now I am wondering if I should bleed the brakes first, that would activate the residual valves in the master cylinder to the approximately 10 psi.
Or does it even matter?


*******ADJUSTING BRAKES ********
ADJUSTING ANCHORS ON ’39-‘41 FORD/MERC BRAKES: These are Ford Lockheed
(not Bendix) brakes and use special brass washers in conjunction with
eccentric anchor bolts to position the shoe. The top of the shoes are
controlled by eccentric cams. The anchor bolts at the bottom of the
backing plate control the shoe position by rotating eccentric washers at
the bottom of the shoes. Before starting to adjust, verify all anchor
bolts turn freely.
The ’39-‘4 use anchor bolts which have locating marks (either a dot or an arrow
for position reference) indented on the elongated ¼” head of the bottom adjusting
bolt. These anchor bolts extend through the backing plates from the drum side
and are adjusted externally after loosening their large external lock nuts.
After adjusting the shoes, the adjustor lock nuts are tightened without
permitting rotation of the anchor pin adjusters.
(1) Always rotate the wheel in the same direction the wheel turns as when the
car moves forward.
(2) Begin by backing all the way off, the two 11/16” eccentric adjusters at the
top of the backing plate until the wheel turns freely. Then slightly loosening
both bottom anchor bolt lock nuts (3/4”) on the back of on backing plate. Turn
all of the two elongated locator marks (either an arrow or a dot) on the 1/4"
adjusters so they face each other.
(3) Further adjustments are made by turning the anchor bolt adjusters in a
SPECIFIC direction.....
(a) Driver’s side. The front shoe anchor ¼” adjuster bolts (with
the dot or arrow) on the both the front and rear wheels are rotated
counter-clockwise when looking at the back of the backing plate. The rear
shoe anchor ¼” adjuster bolts (with the dot or arrow) on both the front
and rear wheels are rotated clockwise. This is VERY important.
(b) Passenger side. The front shoe anchor ¼” adjuster bolts (with
the dot or arrow) on both the front and rear wheels are rotated clockwise
when looking at the back of the backing plate. The rear shoe anchor ¼”
adjuster bolts (with the dot or arrow) on both the front and rear wheels
are rotated counter-clockwise. This is VERY important.
(4) Now turn one of the upper adjusting 11/16" eccentric cams until the wheel
cannot be turned. Adjust its 1/4" anchor bolt in the correct direction until the
wheel just does turn. This lowers the shoe and moves the toe of the shoe away
from the drum, which will result in fuller shoe contact.
(5) Repeat step (4) over and over on the same shoe until turning the anchor bolt
will not free-up the wheel.
(6) Back off the upper anchor pin very slightly until the wheel will just barely
turn. Tighten the anchor pin lock nut (3/4”) and then adjust to the other shoe
on that wheel.
(7) Thereafter, it’s common to never needing to adjust anything other than the
top eccentric cam.
TIP: If you’re installing new shoes, which have been arc-ground to fit the
drum, you normally will not have to go through the preceding exercise. Turn the
dots/arrows until they’re facing towards each other and tighten the ¾” anchor pin
nuts. This correctly positions the brake shoes and you don’t have to go through
the anchor pin adjusting..... just adjust the upper 11/16" cam adjusters.
ADJUSTING ’42-’48 BRAKES: The anchor pins are different than the ‘39-
’41 Lockheed brakes, but do not have any reference marks on the backside
of the anchor bolts. And they adjust differently. Instead they have one
flat side ground on their large round shallow bolt heads. The flat sides
are turned so they face each other. This is usually al the adjustment
needed due to the semi-floating design of the anchors. Tighten the large
nuts (which are on the inside of the brake drum)and put on the brake drum.
Adjust the upper eccentric cams and you’re through.

Re: Adjusting new 39 brake system
 

These instructions are correct for 1939/41.

They are WRONG for 1942/48 which have NO lower bolts or adjustment. Shoes are self centering and are anchored by a non-movable lower pin. Much easier to do as only the upper cams need to be adjusted.

Re: Adjusting new 39 brake system
 

Okay I’m going to adjust the brakes then bleed the system.

Re: Adjusting new 39 brake system
 

Here's more brake bleeding info for 39-41 Fords:

Re: Adjusting new 39 brake system
 

When applying the pressure to the brake pedal per manual it would seem that system would have been bled already for this step to have any effect.(?)

Re: Adjusting new 39 brake system
 

Have the shoes been arched to drum diameter,

Re: Adjusting new 39 brake system
 

cover the shoe surface with chalk and put on and turn and apply brake, this will tell you contact patch

Re: Adjusting new 39 brake system
 

I lined the original shoes. I checked the arc when I put it together and they where very close.
I have to get more brake fluid I have brakes but too much travel in the pedal.
I might use an old A/C vacuum pump to bleed the brakes. It works good pulling fluid while bleeding.
I forgot to bench bleed the M/C but it pumps to all 4 corners with no problem. I might have to bleed it in place.

Re: Adjusting new 39 brake system
 

If you search "bleeding brakes" there will be a lot of long posts, a lot of the new parts are of low quality, the bleeder holes drilled too low allowing trapped air to remain, fluid ports drilled so cup is over hole, ---I take apart all new and resleeved wheel cylinders to inspect the holes and check for debris.
Restoration to original specifications will fix your brake problems. ---I used to have a 39 ,46, now have the 36 BECAUSE it has mechanical brakes, got tired of the total loss of braking, fluid on the shoes causing pulling, grabbing.
try adjusting brakes tight to drum then bleeding that should take shoe movement out of the problem list till you get it bled.

Re: Adjusting new 39 brake system
 

you've changed the master to a duel that operate totally different to a single it can be done but can be tricky to sort out 1 adjust all shoes as per instructions including shoe anchors excessive free play indicates MC out of adjustment spongy pedal ether air in system or incorrect residual valves so make sure your MC is actually drum/drum and valves are installed if so try to locate data that gives residual pressures this may be wrong and may need to remove valves in master and fit inlines to correct the imbalance we are getting into some major engineering that needs to be correct [you may not get a 2nd chance] Talk to someone from your local brake specialist often 1/2 hour talking with an expert can save weeks and $$$$$$$$$ x10

Re: Adjusting new 39 brake system
 

I did tighten the adjustment up and that made a difference. I think if I had air in the system pumping the brakes repeatedly would raise the pedal and it doesn’t. With the wheels off the ground the brake starts to grab in the first inch or so. I think it will be okay. Talk about low quality, some of the bleeders would only take a 10mm wrench.

Re: Adjusting new 39 brake system
 

I have used 66-68 mustang drum/drum MC a few times (that’s what I ordered) I didn’t check but I assumed the MC had 10# residual valve as originals have. I get a little squirt of brake fluid at the wheel cylinder when opened with no pressure on the pedal so that tells me they are probably present and working.
I don’t think it is necessary to remove the residual valves from the master cylinder if you want to add a couple of in-lines ones. They are checking in the same direction. A local brake specialist probably won’t have a lot of input as he wouldn’t have much experience in mix and matching parts. I have experience modifying early HD brakes with Japanese calipers and I had to have the original MC sleeved too smaller piston to match the calliper. Too large of a piston and could cause the brakes to lock prematurely with very little lever movement.
I’m not sure of the piston diameter in the MC I have but I do have an old one that was (mustang) used on a 52 Pontiac. I could compare piston bores just to make sure the oversea junk is all the same. One size larger would certainly make for less pedal movement. Doing the math on volumes of fluid and piston/ wheel cylinder sizes could be done but I don’t need to re-invent the wheel. People have be doing 39 brake conversions on earlier fords for years. The adapter I bought was a Chassis Engineering one that recommended the early ford MC.
I’m a ways away from rolling down the road so a couple spins up and down my driveway with the bare chassis will tell me more.

Re: Adjusting new 39 brake system
 

My understanding is that with the stock 39-41 master cylinder there is no need for bench bleeding. Just install it, fill it, and proceed with the rest of the process. Any problems with this method?

Re: Adjusting new 39 brake system
 

If you have bled out all the air and still have a low pedal, then its a mechanical issue and not about bleeding. Could be the shoes are still too far from the drum, or the free play on the activator rod off the pedal is not adjusted correct, or even the home made pedal travel ratio is incorrect.

Re: Adjusting new 39 brake system
 

Yes I think you are right. I tightened up the brake adjustment and the pedal got better. I adjusted the brake rod so I have just a little travel before contact. I might take it up and down my 400’ driveway and then check the contact between the shoes and drums. Every little tweek is an improvement.
The pedals are stock 39 pedals.

Re: Adjusting new 39 brake system
 

Good news it has improved. Free play on the rod going into the master should just be "felt". no text book answer, just that you know there is some free play to allow the piston to return to its stop point. In your case, perhaps too much, and the opposite if there is too little it will hold pressure if the port to the reservoir is still blocked

Re: Adjusting new 39 brake system
 

36coupe This was the best way to adjust the brakes. I just did mine following these directions. Made total sense and came out perfect. Thanks
I made a copy and put it in my file. Really not necessary, it’s so easy.Thanks

Re: Adjusting new 39 brake system
 

Old post but did not see this question answered? Is it necessary to bench bleed a new 40 master cylinder when replacing the entire braking system with new lines, shoes, fittings, wheel cylinder, etc.?

Re: Adjusting new 39 brake system
 

NO need to bench bleed — I don’t bench bleed most dual master cylinders either— only ones mounted at extreme angles or troublesome systems