I took the drum off the rear passenger, depressed the brake as hard as possible... That didn't even spread the shoes an 1/8" of an inch from the pin at the top.
Well there ya go! That'll narrow it down a lot actually.
You may just have to check for pressure at each junction to see where it stops. If it's not building pressure at the master cylinder you can save a lot of head-scratching.
- I can't get the fronts to lock up, but they are definitely doing the stopping.
But not much it sounds like. While we can't always lock them up you should at least be able to stop confidently on the fronts alone.
Leaning more towards the upper end then. Booster, master, combo valve.
- I installed the proportioning valve that came with the disc brake kit from WH. If it matters, is there any chance I was sent a disc/disc instead of disc/drum??
It does matter, but not that much. Rather than whether it's for discs or drums, it could simply be defective. That's where pressure testing before and after is going to have to be done.
They are not all bad, but it certainly would not be the first time for one to cause trouble.
Regarding what type, when did you purchase? If more than two years ago if you have the rubber boot covering the delay valve, then it's a disc-drum.
If it does not have one, it's a disc/disc.
If it has one, but you purchased it more recently, there's no way to tell (that I know of) other than by the part number etched into the unit.
- I'm not sure, but you may know.....It is the one that came with the power brake kit from WH.
Then it's 1.125" diameter. Normally not a problem in itself when used with a booster. But the lack of pressure at the brakes is the telling tale, and that's not due to the master being too large.
- Best I can remember bleeding was typical. I'm going to try disconnecting the rear line before the flex, and see what kind of flow I have. I'm starting to think the flex line may be compromised on the inside.
Absolutely worth the test. This happens way too often and on any type of vehicle for it to be ignored. If they are original, all the more reason. If they have been replaced at least once, that puts them lower on the list, but still worth checking because there is no rhyme or reason to when one will fail.
- I have not changed them (wheel cylinders), but they look like they have been changed recently. I have had this Bronco 3.5 years. Also, best I can rememer the drum/drum brakes worked as expected before I did the swap.
Ok that's a good sign. It's still possible some debris (possibly from a deteriorating rubber hose for example) got in there and is blocking from inside. Would not hurt to check right down to the bleeder valve itself actually. You can get a clogged bleeder and everything else is fine.
Even though this does not sound like the case, it's still worth narrowing down the variables.
- Vacuum is good, and booster stays firm.
Good vacuum is a good sign, but a firm booster is not necessarily good or bad. Depends on what's making it firm.
If it's firm because the relief valve is not opening properly when you press the pedal, that would be a bad thing.
5. Defective proportioning/combination valve
- This could be possible
Definitely.
7. Rear drums not adjusted out properly.
- Adjusted properly with slight rub when rotating the tires with brake applied
Good too, but now that you know there is little to no pressure at the wheel cylinder, anything going on at the friction surfaces is a moot point right now.
I think you're on the right track. Just have to find out where the pressure is dying.
In my experience with our parts, it's rarely the master cylinder, and we now test every booster so it's very rarely a booster issue. But combination valves continue to be a sore spot. Usually it's a leak out of the delay valve, but in just a couple of cases that I've dealt with, the combination valve kept one customer from being able to bleed the brakes and get a firm pedal, and I don't really remember what the other one was. Just that I sent him a new one.
Let's find that pressure!
Good luck.
Paul
