H block

[GBMAL]

When trying to bleed my drum brakes on my 73 I have not be able to get either of the fronts to release completely.
this leads me to believe the H block is toast. I haven’t been able to locate one and the typical bronco parts places I
only find proportioning valves that specifically refer to disc/drums. My question has anyone had luck at getting an H block to function after locking up? Or, does anyone know if these proportioning valves would serve the same function with straight drums?

 

[gnpenning]

Someone might correct this. Did you put the plastic lock out in before bleeding?

You take out the sending unit for the warning light and screw it in the hole to keep the brakes balanced.

 

[DirtDonk]

How old are the hoses? When they don't release, have you tried cracking open the fitting at the master cylinder?
Since it's both, it's less likely to be the individual hoses at the wheels, but it can still be a bad hose from the frame to the axle.
If it releases when you crack open the fitting, it's probably an issue with the master cylinder. How old is that?

And I could be wrong, because I've heard it both ways for the last 40 years. But it's my understanding that the shuttle moving to one side in the H-block does NOT block flow.
And even if it did, then it seems to me that you would have had trouble even bleeding the fronts. If you can bleed them easily and effectively, then fluid is flowing freely to the fronts. Don't see why it would go only one way if it was an issue with the H-block (sorry, forgot it's precise factory name) having an issue.
I know that actual combination valves can (and often do!) block flow, especially to the fronts. But I'm not aware of that happening with the standard drum H-block.
Otherwise every Bronco with it's Brake Warning Lamp stuck on would have lost front or rear brakes.
Maybe someone can confirm that though.

Paul

 

[Oldtimer]

It could be the hose between master cylinder and H-block.
Also brake shoes can get stuck in low spots worn in 50 year old backing plates.
Pull the drums and take a look.

Partno: C8TZ-2B257-B
Name: Valve-Brake Pressure Differential

The shuttle being tripped (off center) should not block flow of fluid to or from master cylinder.

If leaking, they can be rebuilt with two O-rings and a copper seal.

1967+ Ford Disc/Drum Brake Pressure Differential Switch Kit | Muscle Car Research LLC

www.musclecarresearch.com

 

[DirtDonk]

And you can purchase rebuild kits for old ones, or just get them brand new.
Here's the one we carry: H-Block/Junction Block

 

[gnpenning]

It could be the hose between master cylinder and H-block.
Also brake shoes can get stuck in low spots worn in 50 year old backing plates.
Pull the drums and take a look.

Partno: C8TZ-2B257-B
Name: Valve-Brake Pressure Differential

The shuttle being tripped (off center) should not block flow of fluid to or from master cylinder.

View attachment 932591

If leaking, they can be rebuilt with two O-rings and a copper seal.

1967+ Ford Disc/Drum Brake Pressure Differential Switch Kit | Muscle Car Research LLC

www.musclecarresearch.com

View attachment 932592

Thanks for correcting me.

 

[GBMAL]

Thank you all for the feedback. as usual ,excellent advice. I’ll get started on it.

 

[GBMAL]

How old are the hoses? When they don't release, have you tried cracking open the fitting at the master cylinder?
Since it's both, it's less likely to be the individual hoses at the wheels, but it can still be a bad hose from the frame to the axle.
If it releases when you crack open the fitting, it's probably an issue with the master cylinder. How old is that?

And I could be wrong, because I've heard it both ways for the last 40 years. But it's my understanding that the shuttle moving to one side in the H-block does NOT block flow.
And even if it did, then it seems to me that you would have had trouble even bleeding the fronts. If you can bleed them easily and effectively, then fluid is flowing freely to the fronts. Don't see why it would go only one way if it was an issue with the H-block (sorry, forgot it's precise factory name) having an issue.
I know that actual combination valves can (and often do!) block flow, especially to the fronts. But I'm not aware of that happening with the standard drum H-block.
Otherwise every Bronco with it's Brake Warning Lamp stuck on would have lost front or rear brakes.
Maybe someone can confirm that though.

Paul

Master cylinder is original so a possibility for sure. I think I’ll start there. Thanks for reply and like on WH.

 

[Oldtimer]

How old are the slave cylinders?

 

[ksagis]

My somewhat detailed debuild and inspections of hblocks shows that it will not “block” flow in either toggled position. (@DirtDonk is right as usual!))

You can see in the pics @Oldtimer posted that the smaller diameter tips of the shuttle allows flow past, even when toggled.

 

[DirtDonk]

And we should always add the warning, if you use compressed air to move the shuttle, don’t look down the barrel!
Steer clear, stay clear, stay out of the way, don’t aim it at anything you don’t intend to put a hole in. All those things, your grandpa taught you.