scootchu

I went for a spin in the 67 yesterday and noticed the brakes starting to fade away. I had almost no pedal when I got it home and this morning I had nothing.

I found the problem, a driver's side front wheel cylinder that actually came apart, pistons and all. What a mess.

What concerns me is I changed my master cylinder when I bought the car and it's a dual bowl, I had no fluid in the front bowl and a full rear this morning. So my question is why didn't I at least have rear brakes when the front wheel cylinder failed??

Did I plumb it wrong when I replaced the MC???

I am most likely going with a CSRP disc setup very soon like I did with my 66, but I was curious why I lost everything, yet the rear bowl was full.

In any case the WC that let go was from Advance Auto and I replaced it with an old WC from my 66 today, which works better than the new one.

scootchu

If I am reading the Service Manual correctly my MC is incorrectly plumbed.

I just followed what had already been done.
My secondary bowl is the front bowl and should be plumbed to the rear brakes and the rear bowl is the primary and should feed the front brakes correct???

I think it's reversed, but shouldn't my H valve compensated for the loss of pressure when the WC went not matter how it was plumbed?

hightower2011

Glad to hear you got them back to working. I half expected to read this thread and find out your brakes went out on you mid-driving. I was worried!

JMD

I don't think which bowl is which would have made a difference in your case, what I suspect is that the back brakes were either not entirely bled OR your rear brakes are WAY out of adjustment. (meaning your back brakes NEVER worked after your m/c install).

chockostang

To help a bit, Rear bowl of Master is Front Brakes (Pertains to Drum/Disc brakes), front bowl is rear brakes.

Dan @ Chockostang

scootchu

So with drums the bowls make little difference?

I bled the rears, guess I will have to double check them. The good news is the fronts are great now.

Gregski

Is the H valve the proportioning valve? I don't want to ask a dumb question but does a drum brake setup all the way around still use a proportioning valve? Did they even have proportioning valves back then?

I would raise the car up on a lift and see if your rear brakes work now at all.

67mustang302

Or it could just be that the stock drum brakes suck hardcore by todays standards. They weren't designed to run on modern tires, they were for old polyglass bias ply tires. And most factory stuff especially from the 60's tends to be heavily front biased to prevent oversteering conditions. I'd bet you actually had rear brakes, but just had so little rear braking with enough traction that they couldn't lock(smaller drums with worn shoes would just make it worse). If you had actually had no rear brakes with a completely failed front wheel cylinder you would have had essentially no brakes at all, and it would have taken you absolutely forever to stop.

Newer factory cars with rear drums are running much larger and effective drums for the vehicle size when compared to older cars, and many of them spec ceramic or kevlar based shoe compounds, not organic. But more and more new cars are going to 4 wheel dics....it's hard to get even good drums to keep up with the traction of modern tires, at least not without going to much more expensive drum setups than it's worth.

andrewmp6

Drums are fine when they work most semis still run them on every wheel.But when they act up you have little to no brakes.

Gregski

Your comment doesn't make sense to me. Majority of cars today still have drum rear brakes and last time i checked when we buy tires we buy 4 of the same type of tires, not different ones for the front because we have disc brakes on the front and different ones for the rear because we have drum brakes in the rear.

In addition tire technology has increased leaps and bounds over the last 40 years so if anything tires are stiffer and provide much better grip. If we were to test a vehicle equipped with drum brakes all the way around for stopping distance using vintage tires vs modern tires I am willing to bet (my upside down mortgage) that it would stop in much shorter distance using the modern tires, or the difference would be negligible.