Added Booster, Pedal Travel and No front brakes?

[pipeline010]

So I installed the horsepower booster yesterday, 302 stock drums all around.

No prop valve, just Mc and booster with 8 inch diaphragm.

Bled the system (I think) and the pedal travel is extreme. No stopping until the pedal is almost to the floor, gives gradual stopping to dead stop within a half inch of movement.

During bleeding I had to clean a few bleeder screws that were jammed up with gunk (dirt not rust), and I believe I've got it clear or at least near enough that the travel shouldn't be that bad.

MC rod was preadjusted, but I did my own adjustmentsprior to attaching the MC and found that Dan had already had it at the perfect spot.

Any suggestions? ?

 

[B RON CO]

Hi, did you bench bleed the master cylinder first? Good luck

 

[pipeline010]

I did, ya. And tested. It squirted fast and far.

 

[pipeline010]

update:

wife had to go to work, so using that junky Mytec hand pump to try to bleed. i've got a comical amount of air coming through the lines into the handheld reservoir now.

not sure if that's the issue or the mytec hand pump is as crappy as everyone says at one-man bleeding.

note: i've officially put over 1qt of new brake fluid through this system now. much of it is now in an old milk jug and/or laying on my driveway.

 

[B RON CO]

Hi, you could crack open a bleeder, one at a time, and let it gravity bleed.
Some one man vacuum bleeders work great. I have the Mity Vac Silver line.
When you get a helper, pump the pedal nice and slowly 3 or4 times before opening the screw.
I'm sure you are keeping the master cylinder full.
If there is a small leak at one of the connections it will cause your problem.
I'm guessing your helper is holding the pedal down while the screw is open, and letting it up after the screw is closed. Also bleeding from the longest line, around to the shortest line.
Good luck

 

[pipeline010]

Thanks Ron. Fairly certain we bled it through, using the exact method you described.

When I used a partner she pumped 5-10x held, open screw/closed screw, pedal release. We didn't redo the rears because that is where the braking is currently coming from (the truck is totally driveable, kinda, just a pedal that's way way too low and only braking from rear).

With the mytek I eventually got even movement of brake fluid on both sides of the front with absolutely no air through.

Checked with vacuum gauge on the booster line, got 20hg ..with a bouncy needle, but I just reset timing yesterday (10*) and haven't retuned carb yet, so unrelated issue. So booster is getting the vacuum it needs.

been checking the line for leaks, haven't found anything but I'll continue looking. After bleeding with the hand pump i did hear a steady wheezing sound coming from the master cylinder, but figured that was normal depressurizing from the hand pump.

 

[pipeline010]

searching the random web I came across this forum and a post from someone that just happens to have a FS bronco with literally EXACTLY the same issue.

I know it's been said to death, but ya..I think I messed up with the length adjustment on the MC rod. I ran out in the almost dark and ran the rod out a bit longer and hastily put it all together again to test. Still the same issue, but I didn't really measure properly. I was shocked that I had that much space with which to move it out..I must have more.

99% this is my issue.

https://www.ford-trucks.com/forums/...nd-master-cylinder-and-now-have-no-pedal.html

 

[DirtDonk]

Does the rod go far enough out? Did your master come with either a shallow piston, or one of those spacer thingies that takes up the space?

If you don't have proper measuring tools (it's awkward sometimes anyway) just turn it out until your master bottoms on the rod before it bottoms on the mounting surface of the booster, then start turning it back in until you can seat the master to the booster just before the rod hits the back of the piston.
There is a specification of course, but it's a very small gap.

But don't forget there is also the pedal rod length, and cantilever length as well. Make sure you don't have excess play in all three areas or you'll be stacking those tolerances on one another until your pedal almost hits the floor!

And it sounds like you did not mess with the calipers prior to this happening, correct?
You only messed with the booster and master before this started, right?

Good luck.

Paul

 

[pipeline010]

Drum brakes, but nope no adjustments there. I'm rebuilding the brake system but doing it all one part at a time to be sure which part I inevitably installed incorrectly.

But thanks Paul, I watched Nashvilles video on the install, kinda ignored the part where he said to measure out the rod. I truly thought I had no room to play until I finally made an adjustment and found I had room. It was super hasty (due to darkness coming, I was outdoors), but I think I pulled it out about 1/2" before putting it back on. I didn't notice a difference in pedal play, but there may have been a slight improvement. I just wanted to get my tools back inside before dark as it was set to rain today so wasn't paying very good attention.

I'll report back if I brave the rain this afternoon to get it done. Thanks.

 

[pipeline010]

no dice.

master cylinder rod - brought it out until MC bottomed out, brought it back in very very minimally until the MC would seat. Still no difference.

Paul - sorry if this is dumb, but why would the pedal length affect the travel? the push rod that connects to the actual pedal screws in and out, so wouldn't that effectively mean every position would be the same in relation to the push on the booster/MC?

Do I have anything left to adjust?

note-could be possible all this on/off is requiring more bleeding (obviously it does), but I'm not betting bleeding would fix the issue as the pedal is in the exact same position of engagement it was before the adjustment. Would be one hell of a coincidence that the distance adjustment would be perfectly offset by the need to bleed. right?

 

[B RON CO]

Hi, how did the brake pedal feel before?
If the brakes are way out of adjustment you should wind them up so the shoes just scrape the drums.
The out of adjustment feel goes away if you pump the pedal. Good luck

 

[DirtDonk]

Definitely that. But for this go-round, all you changed was to the booster, correct? New master as well I think you said, right?
If so, and it was firmer before, then I'd have to say to keep suspecting the new install. Yes, strange things happen, but this is pretty straightforward (seemingly) so not sure what all else, other than air in the system, could be doing it.

You did re-plumb the front brakes to the rear reservoir, and the rear brakes to the front, of the new master. Correct?

I can't say for sure that the location of the pedal rod would do this, but if it's not engaging things immediately, remember that everything is magnified by 6 to 8 times at the pedal due to the pedal-ratio.
Which is why the piston/booster rod adjustment is so critical. A quarter inch there equals and inch and a half at least at the pedal.
But the pedal rod? I'm not 100% sure. I might just effect the pedal height and nothing else. Just wanted you to make sure all the linkage was doing what it was supposed to.

Maybe the booster and/or master are defective. It does happen, but usually it's the other way 'round, with the booster just being too hard to push. Not too soft.
And speaking of that... When it does reach near the floor is it at all spongy feeling? Or is it solid when it works?
Maybe there's air in just one circuit (the front) instead of both, or up near the master.

No discs up front, so no chance the bleeder screw is down. No proportioning valve though, correct? Just the old H-block on the frame?

Paul

 

[pipeline010]

Yep, just H-block straight to the MC, no prop valve.

Drums all the way around, i had to give the bleeders the business to get them loose, including removal and cleaning old mud out of one of them, but they seem very intact and holding.

Rear (bigger) is for the front, drivers side of h-block. Front (smaller) reservoir is for the rear, passengers side of the block.

Prior to the install the brakes engaged proper right at about 5.5-6" pedal from the floor, almost zero travel. Nice hard pedal.

For now, I push and it's like absolutely nothing until it's about 1-1.5" from the floor and then, in that range of motion, I can go from slow stopping to immediate stopping. I have a feeling the front brakes aren't engaging at all, but I'm not sure on this.

Checked the booster by turning the truck off, the pedal stiffens up almost immediately right at the top of the range of motion, right where it should. Once the booster is activated (vacuum) that pedal feel goes away again. I suppose it could just be the MC, but not sure how I would diagnose that. During bench bleeding the fluid moved seemingly just fine.

 

[DirtDonk]

Well that's a pretty good description.
The fact that the pedal goes stiff at the top with no vacuum says to me that the pedal-to-cantilever, and cantilever-to-booster rods are pretty well within spec.
The fact that it goes to the floor (almost) when vacuum is applied says to me that the booster is doing it's job.
And since, as far as I know at least, the connection from the input of the booster to the output rod of the booster is pretty linear and direct, it sounds like the booster itself is fine.
And since you now know that you've adjusted the rod out to the point it's almost touching the piston with no pedal pressure, it seems that the trouble must be in the master itself, or with air in the lines.

Another experiment that's just a "what if" kind of thing, would be to take it around the block and apply the brakes to get a feel, then push on the parking brake a couple of notches and apply the brakes again. If it gains pedal height noticeably, then you can at least gain a tiny bit back by re-adjusting the rear shoes.
This is not a cure, and does not address your underlying problem. Just one more level of information to rule things out, more than anything else.

After all this has been going on, I would take a close look at the bleeders again too. Because you had some trouble with them, perhaps one or more of them is actually leaking slightly and allowing air back in. Not leaking enough to make a big mess, but maybe enough to let a little fluid out to give you a clue that they're having some effect here.

Paul

 

[B RON CO]

Hi, every bad booster I've seen turned rock hard when you press the pedal. Good luck

 

[pipeline010]

all good tips, as always, thanks.

Ya I think the booster is good...it's doing what it's supposed to do, anyway. Just real low to the floor.

Hypothetical - let's say I measured my pedal at 6" from the floor, but then, after installation, replaced the pedal at 10" from the floor. Would this cause the situation I'm dealing with?

It wouldn't be that drastic, but it's possible my measurement was slightly off. That coupled with air in the fronts could potentially be the issue?

Last item for now: I completely unscrewed that pedal coupler arm (or whatever. tie rod?) from the interior inside the firewall to test its press upon my brake light indicator (which it failed, but I can shave some metal off with the DA). Now, I know how they work but am not completely clear on the internals; when I screwed it back in could I have missed something that could be causing this?

Doubtful, but maybe something there. Thanks.

 

[66broncoCT]

I noticed when asked about bench bleeding the master you said you did and it squirted fast and far. What did you mean by this? How did you bleed the master cylinder the plugged ports method or the returning fluid way?

 

[pipeline010]

i actually did it on a bench, tubes from outlets back into reservoirs. then I installed but couldn't do the brake lines cause I didn't have line pliers.

my mechanic did (who was there later to help me set my timing) had me press the brake to see if I did the bench bleed correctly before he plugged the wires. Didn't move the brake a 1/2" before he said "stop!stop! it's good!" ....it cleared the air filter.

 

[bronkenn]

i actually did it on a bench, tubes from outlets back into reservoirs. then I installed but couldn't do the brake lines cause I didn't have line pliers.

my mechanic did (who was there later to help me set my timing) had me press the brake to see if I did the bench bleed correctly before he plugged the wires. Didn't move the brake a 1/2" before he said "stop!stop! it's good!" ....it cleared the air filter.

Then when the pedal was released it could have sucked air in.

 

[pipeline010]

ya true. the only way to clear air within the MC is to bench bleed?