I have pretty much rebuilt all four drum brakes on my 51 F-1. I have bled them and adjusted them (there is a little friction when I free-spin the wheels). There are no fluid leaks in the system. But despite all that, my brakes are still pretty mushy, almost like they've never been bled. So that leaves the master cylinder, right? It looks pretty rough, the boot is totally shot, but it is not leaking fluid and the reservoir is and remains full. It IS sending pressure to the brakes, just maybe not enough. I am thinking the MC piston and or the cylinder walls are bad and a lot of the brake fluid is not getting pushed downstream. Does this seem like a reasonable analysis? Should I go ahead and change out the MC?

Thanks!
Tyler

 

I had to rebuild the master cylinder on my 49. It was pretty nasty. Its a single reservoir, they are pretty easy to rebuild. I dont know about a 51. Did you replace the rubber brake lines? Did you flush out all the old fluid. Sometime there can be a little moister in there that will can cause some problems.

 

Tucson is certainly having it's brake problems! I'm no expert as I have similar problems but it sounds like the seals on the piston like rings in a cylinder, are not holding pressure and allowing the fluid to bypass back into the res. Or you might have pumped the pedal while the bleeder was open allowing the air back in and you are just bleeding the wheel cyl. each time. Bill

 

if all else fails try the "stick trick". Cut a broomstick to length, jam it between the front of the seat with pedal as far to the floor as possible. Leave it like this for 12 to 24 hours. I know it sounds strange but I've done this to 3 different vehicles with mushy pedals and its worked each time. I was shown this trick in the 70's by a old mechanic who was close to 80 then.
Works for me.

 

Tyler,

Depending on where you live, working brakes can be an important feature. Arizona is one of the places where you'll probably need them before too long.

Since you've already spent the time on rebuilding your wheel cylinders, you should probably go through the master cylinder too. You have three basic options....replace it with a new one, install a rebuild kit, or have a local brake/steering shop rebuild it for you.

The new one is $125 at dennis carpenter, or $30 for the rebuild kit.

You should also check the flexible brake lines. Those can age just like the internal parts on your wheel cylinders (don't forget the one in the back).

All that being said, you may simply need to bleed the brakes more. It takes a lot of bleeding to get bubbles out of the lines if they are stuck at the higher points in your system. Start with the wheel that is furthest away from the master cylinder (so...right rear), then move to the next closest wheel (left rear)...then right front and last...left front. You may have to go back & re-bleed the right rear as a last step. If you still have problems, get a cheap suction pump and bleed out the system with suction rather than pressure. That tool allows you to get a bigger volume of fluid to flow through the system & suck the air bubbles out. What can happen with conventional bleeding...if you start forcing a bubble down towards the wheel cylinder, then stop...shut the bleeder, re-fill the reservior, then start pumping again...the bubble can rise back up in the line before you get it worked out.

Consider this thought for a moment....imagine yourself cruising your newly running F1 down the road....when the car in front of you stops short to turn into a driveway....as you apply the brakes, you think to yourself...damn...I wish I'd spent the $125 on a new master cylinder!!!

Dan

 

You can get that master cylinder for a LOT less than $125 if you go to NAPA, Advance, Auto Zone, etc. They usually can have it the next day.

 

Sounds pretty whacky. I am curious what this actually does to help the brake system. Any ideas?

t

 

The system has been flushed but maybe I should try again. I guess I can try bleeding again too. I have no problem replacing the master cylinder if that is the most likely cause of my problems. I intend to replace the brakes with discs eventually as part of the rebuild but would like the old drums to work in the mean time for two reasons:

1: I would like to test drive the truck to see how the engine and tranny actually perform under a load before proceeding with the rest of the rebuild. If the engine is shot (351W installed in 70s I think) or has many expensive repairs AND I have to replace the transmission, then I might take a different (more cost-conscious) route to rebuild the rest of the car than if I don't have as many engine or tranny problems.

2. This is my first project on the way to the rebuild of this truck and I WILL NOT BE DEFEATED! NO WAY, NO HOW!!

I need a beer.

t

 

If you have some wheel ramps of jack stands get the passenger side up in the air for a few hrs - Rebleed the elevated side.
I had the local Ford dealer replace the front to rear brake line - The next day my brakes were mushie - I took it back and they said there was no way that there was air in the system as the used a power bleeder - I aks them to amuse an Old Fart and put the passenger side in the air, let it set for an hr. or so and bleed the right side again - They struck air - They wanted to know how I knew this - I told them that I used to work on airplanes and when we bled the brakes we would fly with one side up at a time and crawl thru the hatch and bleed that side then switch - They were still standing there talkin as I drove away.

 

I had the same thought about the piston, Bill. Never thought of the bleeder screw issue though. Simple enough to rebleed. It's worth a try.

Thanks!

t

 

If there is any question at all about the condition of the MC, change it. Change the pressure switch for the stop lights while you are at it. Cheap insurance.
And like others mentioned, make sure hoses are good, lines are not rusted.

 

Hey Tyler,
I had pretty much the same experience with our '50. The brakes & steering were scary bad. I'll take a different tack - you are putting a lot of effort into old drum brakes. At a minimum put a dual chamber master cylinder in there - better yet put a front disc brake kit on there & you never have to worry about them again. I changed out the front brakes after coming to a stop with my foot all the way to the floor & I was still moving forward. This is not the area to mess around with even if it's just going around the block or on test runs. I never could get the drums to work well enough - modern brakes make all the difference. Good luck over there.

Ben in Austin

 

The Stick Trick.....
It works because it uncovers the by-pass port and atmospheric pressure draws out
the last remaining little air bubbles.
Air going into the solution , causes squishy brakes as air is compressable.
If nothing else works for you, try it all you waste is a overnight.

 

OK! I'll give it a try!

t

 

Ben, or anyone else,

Can I bolt in a dual chamber master cylinder or will it require other mods/fab to mount it?

I assume a dual chamber MC isolates front from back or something like that so that a single failure or leak doesn't dump the whole system leaving you brakeless?

t