1975 Bronco brake problems and questions.

[Proeliator]

So, I abruptly lost the majority of my brake ability the other day. Factory drum brakes all the way around. After pulling the wheels and drums off, I found I have no leaks at the wheel cylinders (or the master cylinder for that matter), and most oddly there seems to be zero pressure reaching the front brakes only. System has been bled, and the pedal is solid.

All I can think of is that something failed in the master cylinder (clogged?) which caused this. I did notice something that looks like a proportioning valve downstream from the master cylinder with an electrical connection running to it. My understanding is that only disk/drum setups utilize proportioning valves, so I'm thinking this must just be some sort of distribution block, although for the life of me I can't imagine what the electrical connection running to it could be. So, this could be a culprit for a clog/failure as well since the rear brakes work and both fronts have no pressure. Just wondering what the heck this is and figured you guys would know.

Honestly, I'm seriously thinking about springing for the power front disc brake conversion that TBP sells at this point. Just curious what you guys think about the failure issue and what the heck exactly the deal is with the distribution block/proportioning valve/whatever the heck it is with the electrical connection.

Thanks in advance.

 

[bronconut73]

That distribution block sends a signal to the brake warning light.

You could have swelled up flex lines.
They can really go to shit on the inside where you can't see.
It will block some fluid for sure.

 

[Proeliator]

Ah, thanks! I figured it had to be just a simple distribution block but was scratching my head over what the heck the electrical component was for.

Valid point about the flex lines, although I really doubt both sides on the front crapped the bed at the precise same moment.

Follow up question, who's aftermarket power front disc brake kit is currently considered the best? Wild horses, TBP...?

Thank you for the input. The wife is going to start driving this one and I want to make sure the brakes are in tip top shape.

 

[bronconut73]

Those guys are both great.
The real question is all Ford or the Chevy conversion with Ford rotors.
They are very similar in actual braking force.
The GM style will arguably hold less mud and remain more free in off roads tough conditions.
But the GM caliper mount is steel and it will flex. You will feel this in the pedal with more travel.
The Ford caliper mount is cast iron. It will not flex. You feel this at the pedal with a stiffer more solid pedal.
The Ford mount may hold more mud but I believe it is technically the better system.
Having said all of that I run the GM conversion front and rear. Excellent and much cheaper.

 

[bigsil48]

Sounds like the rubber line going to front axle has collapsed. But ya never know till you start your inspection. I have a 67 that just this past week, I swapped the D30 front drum axle for a 74 D44. I bought bare housing and have built every component the way I want. Spool, Chromoly axles, F150 knuckles, extreme spindle bushings, Dura solid spindles, had the hubs and brackets from a 78 bronco from my local pull a part. ALL FORD!!! And Stronger!
77 T Bird calipers. Hoses I'm getting from Jegs. They are 18" SS braided w/ 7/16" banjo and -3 female. Also 7/16-24 banjo bolts from Jegs.
Got the booster set up from Ebay (Toms Classics). $250
My D30 Drum axle is all good and has the dealer option WARN lockouts that are super strong. Anyone in TN need one its 4 SALE!!!

 

[elemetal]

The proportioning device serves two functions: one is to supply a different back pressure to the drum rears vs disc fronts (not an issue with yours); the other is to still allow braking pressure to either of the ports out even if one of the sides is blown out. There is a small sealed shuttle inside the valve that is held in a neutral balance position when both front and rears have pressure. If one set (front or rear) loses all pressure the shuttle gets pushed to that side and seals it off so at least the other side can still hold pressure. Sounds like it went to one side for whatever reason and is staying there.
You can pull it out of the pressure and see if you can re-center it but check to see which port it moved towards, you may have a leak on that side which caused the original movement....