1939 master cylinder

[Woodie1]

I want to replace the master cylinder on our 1939 Ford. I'm thinking if I remove the brake lines at the rear fitting & remove the wires to the brake switch, I should be able to remove the 3 mounting bolts for the cylinder, & the controls at the front of the cylinder can be left alone. Am I seeing this right or am I missing something?

[Kube]

Originally Posted by Woodie1

I want to replace the master cylinder on our 1939 Ford. I'm thinking if I remove the brake lines at the rear fitting & remove the wires to the brake switch, I should be able to remove the 3 mounting bolts for the cylinder, & the controls at the front of the cylinder can be left alone. Am I seeing this right or am I missing something?

You should, with some patience, be able to R&R the cylinder with the lines connected to the brass fitting. Simply remove the bolt with the switch.

[Woodie1]

I hadn't thought of that Kube. That would save me a little time.

[Flathead Fever]

Bleed the master cylinder before you hook up the lines.

[rich b]

Anneal the copper washers; whether new or old being reused.

It would be a good idea to make sure the pushrod adjustment is free while the master is off; just in case it is needed with the new master.

[Woodie1]

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I took the new master cylinder off. I could not bleed the brakes. Most of what I read said it wasn't necessary to bleed the single port master. I'm trying to bench bleed it with no luck. I keep getting weeping at the rear of the cylinder & air bubbles keep forming at the intake port. I put on a new brass fitting at the rear of the master along with 2 new washers. I have the brake switch mounted. What am I missing? I'm about ready to get a rebuild kit for the old master & try bleeding that one.

[Kube]

Originally Posted by Woodie1

I took the new master cylinder off. I could not bleed the brakes. Most of what I read said it wasn't necessary to bleed the single port master. I'm trying to bench bleed it with no luck. I keep getting weeping at the rear of the cylinder & air bubbles keep forming at the intake port. I put on a new brass fitting at the rear of the master along with 2 new washers. I have the brake switch mounted. What am I missing? I'm about ready to get a rebuild kit for the old master & try bleeding that one.

It's possible the master is defective. It happens. There is no need to bench bleed a single cylinder master.
The weeping? That's probably your issue. If it's weeping fluid, it is sucking air. You need to get those washers to seal completely.

[Woodie1]

I have read on here that the bench bleeding wasn't needed. I was getting desperate as I can't get a good brake pedal by bleeding the wheel cylinders. I've tightened the fittings as much as I dare. It was mentioned to anneal the washers.

[Terry,OH]

The master cylinder piston has a seal around it at the end toward the operating rod, if that seal leaks it willl allow air to enter.

[Woodie1]

Does the angle the car sits at make a difference in the bleed out of the air in the wheel cylinders? I read where 1 person had lowered his front axle for the bleeding process.

[petehoovie]

Originally Posted by Terry,OH

The master cylinder piston has a seal around it at the end toward the operating rod, if that seal leaks it willl allow air to enter.

[Woodie1]

I got tired of bench bleeding the master. I put it on the car. I had the 2 brake line holes plugged. The brake pedal was hard & didn't go down. I hooked up the front brake line & the pedal was still hard. Hooked up the rear brake line & now the pedal was low. I had the brake shoes tight against the drums so I wasn't loosing movement there. Now I wonder if the new master is bad. We bled all 4 wheels 4 times around & no improvement.

[mhsprecher]

What order did you bleed the brakes?

[Woodie1]

Passenger rear, driver rear, passenger front, driver front was the sequence.

[Kube]

As Terry and I (posts 7 & 9) have suggested, a defective master is a possibility. Me? At this point I'd obtain a replacement.
NAPA sells NEW (not rebuilt) cylinders that I have had nothing but good fortune with. About $55.
The listing, when you go there, is under 1948 Ford.

[Woodie1]

I will get a replacement master. It just surprises me that I had good pressure with half of the brake lines connected & bad with the other half connected also.

[FlatheadTed]

Could be a displacement issue ,to big wheel cylinders or to small M/C -1,1/8 ,one pipe hooked up the piston can fill the front ect .

unlikely ,but is this a Duel out let ? Could be You had one out let blocked so the fluid was backed up against that rendering the other one not working ,you then hooked up the other pipe allowing fluid flow into it result soft padal ,

[Terry,OH]

If the fronts are on and the pedal is good I would look at the rear brake system. Maybe block the flex hose and then see if there is still pedal.

[Woodie1]

I misspoke myself. The rears gave good pedal & the fronts went soft & low.

[Woodie1]

I got a new master from Napa. It is better but I still get air no mater how may times we bleed the system. I think we bled at least 8 times all around. I also lengthened the master push rod. I get braking after the pedal goes down about 3".