Brakes Siezing

[Drbrown]

After driving a short distance and first using brakes, the brake system siezes up, slows the car down and when stopping the car it comes to an abrupt halt as if the brake pedal is firmly applied. If the car then sits for a day everything returns to normal. System was flushed and self-bleeders installed about a year ago. I assume I should start by jacking entire car up to check individual wheels and check for pedal free play, which SEEMS absent when the system is siezed-up. Any advise appreciated. If it comes down to the Master Cylinder, any recommendations re good place to buy one ?.

[hueyhoolihan]

can we assume the car stops in a straight line?

if so, i would be thinking (and i no expert whatsoever) it was a master cylinder problem. or at least something involving it or the line that exits the master cylinder until it reaches the first junction.

and can we assume we're talking about a '47 ford sedan?

[ford38v8]

Brake drums will develop minor surface rust if not used often enough. First application of brakes after sitting for a while will remove that surface rust, which causes a shuddering of the shoes/drums, no damage, just freshening of the contact area.

[Als48]

Hi Dr B,

Are your brakes OEM original style drum brakes? It might help with diagnosis if we knew what you are dealing with. I once had a disc brake caliper dragging on an RV which caused me numerous headaches in diagnosing. It was losing its brakes after driving for a while for no apparent reason (to me at least). Pedal would go to the floor, basically no brakes except for the parking brake, which would slow the vehicle but wouldn't do it very fast. Scary to say the least! The fix was pretty simple once I discovered the front wheel was getting very hot due to the disc caliper dragging. This, in my opinion was heating up the brake fluid enough to vaporize it, at which point I would lose my pedal feel with little to no braking. Changing the caliper fixed the problem, and the brakes were fine. Whew! Very scary at the time.

Al Hook

[Ggmac]

I had similar, but it was the internal c clip holding the master assembly together. It broke and left the end piece in the bottom of the bore . Every time you hit the brakes the pressure would rise .
Could be the back center flex line , or front flex line but the front would cause a pull

[Mart]

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Possible culprits:
Brake pedal push rod needs adjusting (too long).
Recuperation port blocked in master cylinder.
Pedal pivot tight, preventing pedal from returning fully.
Pedal/pushrod pivot tight, preventing pedal from returning fully.
Collapsed flexy hose.
Master cylinder just plain clogged up.

If flexy hose, each hose would affect different wheels.

Can you lift the pedal with your toe? Does it return smartly due to it's own spring?

It all points to fluid not returning to the master cylinder. the fluid gets trapped in the system and expands as it gets hotter the dragging brakes make it hotter and causes it to put the brakes on harder until you can't move. Once cooled down they will ease off and the cycle can start again.

Is the push rod a nice loose rattling fit?

Mart.

[B Munroe]

Make sure your brake pedal is returning all the way up. If the rod going to the master cylinder doesn't return all the way back the hole in the master cylinder that allows the brake fluid return to and from the reservoir will not be exposed. The brake fluid will heat up and expand. If it has nowhere to go it will push out on the wheel cylinders.
Another issue to look for is if the rubber hoses have started to break down the inside will close up and not allow the fluid to return toward the reservoir.
(I posted the same time as MART above) Good info.

[RalphG]

Had a similar problem on the front disks on a square body GM. It was the rubber line swollen inside that prevented the brake fluid from returning when the pedal was released. It took a while for the pressure to drop.
Another time had a similar event on an old early 50s GM pickup. Actually got under it and partially opened a wheel cylinder bleed screw to let out the steaming hot fluid. Its too long ago to recall how we fixed that problem but on the newer truck it was just a matter of new front rubber hoses to fix it.

[rich b]

Most common and easiest cause to check (especially after being parked for the winter) is the brake pedal not fully returning.

Check that the pedal pivot is free and the return spring pull it up against the rubber bumper.

Check that the master cylinder push-rod has a slight bit of free play when the pedal retracts. Better to actually get under the car and check this.

If that seems OK, pull the boot back on the master and check that the piston comes back against the retainer washer.

If the fluid is clear you can look down inside the master to see this too.

While hoses go bad it is usually only one wheel and does not have as drastic lock up as you describe (usually just results in drag and a single "hot" brake.

Obviously your results may vary.

[Flathead Fever]

I agree with rich b. The first thing I would check is the master cylinder's piston is returning all the way back against the keeper, possibly from the rod being adjusted too tight. There needs to be a little gap so that when the piston comes back it uncovers the return port for the fluid, otherwise the brakes will lockup and stay locked up until the pressure slowly bleeds off.

[Drbrown]

Who is selling Master Cylinders (rebuilt ot NOS) ?

[Kube]

Originally Posted by Drbrown

Who is selling Master Cylinders (rebuilt ot NOS) ?

Napa sells very good quality NEW master cylinders. A bunch cheaper than the "usual sellers".
Their part #: NMC M1050. They list it at $95. I get a discount and bought one not four weeks ago, $55.

[51504bat]

When I first got my '39 p/u I had the same issue. The PO had done a complete brake job but used and off shore m/c. I replaced it with a USA made new Wagner that I got from Joe's. Problem solved.

[Drbrown]

I'm a bit surprised regarding NAPA. Following-up I went to my NAPA store and got a price for the M1050 Master cylinder .... $150 ! Ouch ! They said it is a Dorman M1050 unit but couldn't say if it was US made. Went to Summit Web Site where they sell the Dorman M1050 for $61 plus shipping and tax = $80.

[hueyhoolihan]

Originally Posted by Drbrown

I'm a bit surprised regarding NAPA. Following-up I went to my NAPA store and got a price for the M1050 Master cylinder .... $150 ! Ouch ! They said it is a Dorman M1050 unit but couldn't say if it was US made. Went to Summit Web Site where they sell the Dorman M1050 for $61 plus shipping and tax = $80.

yes, it pays to shop around! i've found that searching for the best price on the internet pays a decent hourly tax-free rate! a 20%+ savings is not uncommon.

[Mart]

I would dismantle it and wash it out thoroughly. Cheap insurance. It might already be clean but at least you will know it is clean. I have got a surprising amount of rubbish out of master cylinders but not sure if it was this exact model.