100% new brake system 0% pedal (1 Viewer)

sloanstavern

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Good question?

Quick update, I have all four corners adjusted properly. Found the master cylinder and lines have had 3 quarts of clean brake fluid run through them and no evidence of remaining trap there. However I did notice that the booster seems to make no difference, by using this test with the engine idling I applied pressure to the break and then turned the engine off pedal did not move, then with the engine off I depress the brake and started it pedal did not move. The check valve is operative but I have no idea what’s going on inside that booster any other tests I should be doing?
 
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Bench bleeding the master shouldn't take more than a few strokes, it doesn't have the capacity to hold much air. I can't imagine if you're bleeding correctly running that quantity of fluid through and still having air in the system. What I can imagine is the shoes settling in and squaring themselves up relative to the drums after being driven and now there is clearance where before, where everything was sitting on initial assembly there was none and pedal was good. I'd pull drums and verify light snug slip fit between shoes and drum faces all the way around.
 

sloanstavern

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Bench bleeding the master shouldn't take more than a few strokes, it doesn't have the capacity to hold much air. I can't imagine if you're bleeding correctly running that quantity of fluid through and still having air in the system. What I can imagine is the shoes settling in and squaring themselves up relative to the drums after being driven and now there is clearance where before, where everything was sitting on initial assembly there was none and pedal was good. I'd pull drums and verify light snug slip fit between shoes and drum faces all the way around.
Thanks I’ll give it a shot.

Could a failed booster contribute?
 

Skreddy

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Good question?

Quick update, I have all four corners adjusted properly. Found the master cylinder and lines have had 3 quarts of clean brake fluid run through them and no evidence of remaining trap there. However I did notice that the booster seems to make no difference, by using this test with the engine idling I applied pressure to the break and then turned the engine off pedal did not move, then with the engine off I depress the brake and started it pedal did not move. The check valve is operative but I have no idea what’s going on inside that booster any other tests I should be doing?
Have you hooked up a vacuum gauge to see if you have a leak?
A quick test: engine running, clamp the soft line to the booster with vice grips, any change in engine? Now release vice grips quickly, any change?
All that said, bad booster would only make the pedal require more effort for same stopping. Should still stop.
 

sloanstavern

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Have you hooked up a vacuum gauge to see if you have a leak?
A quick test: engine running, clamp the soft line to the booster with vice grips, any change in engine? Now release vice grips quickly, any change?
All that said, bad booster would only make the pedal require more effort for same stopping. Should still stop.
Thanks - I did clamp and release that line, no difference. I tried to pull a vacuum with my hand pump, no joy. I believe It is DOA, but I was not sure if that would show up as a soft pedal. thanks for the confirmation.
 
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Thanks - I did clamp and release that line, no difference. I tried to pull a vacuum with my hand pump, no joy. I believe It is DOA, but I was not sure if that would show up as a soft pedal. thanks for the confirmation.
Failed booster should just become manual brakes and will be hard pedal and excessive force needed to stop. Will have no part in the pumping you have to do to get pedal.
 
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You mentioned earlier that you are vaccuum bleeding the system. Personally, I havent had good luck with that on my 77. I do old school, and talk a kid/wife into pumping and manually bleeding.

I dont know why, but every time I have flushed the fluid using a one person method the rear drums get wonky. Front discs do fine. Try manual bleeding and see if it helps.
 

sloanstavern

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I agree, 2-man best.

The vacuum bleed was useless. My one man method of choice is longer clear tube over the valve tight, then up over the tire down into a bottle.
I only open the valves 1/8 turn so air can’t get in through the loose thread.
 
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I know the shoes are adjusted OK because after a few pumps the pedal is rock solid.
@sloanstavern I meant to chime in earlier, but I thought that you had solved your issue with the MC discussion. I think that you might NOT have the proper adjustment on the brake shoes. Having to pump the pedal in order to get it firm is a classic example of being not quite tight enough on the shoe adjustment. Just because a wheel was locked up when you did the initial adjustment doesn’t mean both shoes on that wheel are fully tight. First, pick a side to start on. Adjust a single wheel cylinder until the wheel locks up then back it off just one click at a time until you can spin it with a dragging shoe. Now, repeat that procedure exactly with the opposing wheel cylinder on that same wheel. Simply repeat these steps exactly with the other wheel on your rig. You now have both shoes adjusted as tight as they should be. There will be a lot of drag. More than you think there should be. If your shoes are new you’ll wear off some of that surface grit on the first test drive. They will smell warm, but not burning. I hope this helps.
 

sloanstavern

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@sloanstavern I meant to chime in earlier, but I thought that you had solved your issue with the MC discussion. I think that you might NOT have the proper adjustment on the brake shoes. Having to pump the pedal in order to get it firm is a classic example of being not quite tight enough on the shoe adjustment. Just because a wheel was locked up when you did the initial adjustment doesn’t mean both shoes on that wheel are fully tight. First, pick a side to start on. Adjust a single wheel cylinder until the wheel locks up then back it off just one click at a time until you can spin it with a dragging shoe. Now, repeat that procedure exactly with the opposing wheel cylinder on that same wheel. Simply repeat these steps exactly with the other wheel on your rig. You now have both shoes adjusted as tight as they should be. There will be a lot of drag. More than you think there should be. If your shoes are new you’ll wear off some of that surface grit on the first test drive. They will smell warm, but not burning. I hope this helps.
Thanks for the tips - Here is what I have done in that regard.

Multiple times, I tightened all adjusters ( 4 in front 2 in rear) then depressed pedal to "center" shoes. Repeated until I could not tightern any further, then back off 1-2 notches so that the wheels barley turned. - NO JOY

Today I cranked all adjusters down till stop, pressed pedal , repeat until I could not tighten further. All 4 wheels are fully locked by brake shoes .

I measured pedal travel before and after:
Before - At rest 8.25"
Fully pressed 5.0"

After Fully pressed 5.0" No change

Here is how the pedal is traveling:
At rest 8.25"
First press 5.0"
send press 6.5"
Third Press 7"

Signed,
Flumexecd.....
 
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Sounds like your shoes are all tight. In all your attempts at bleeding, did you try the old-fashioned 2-person method with a kid pushing hard on the pedal? This is the ONLY way I have been fully successful. This will result in a huge gush out the bleeder with no chance of air getting sucked back in if you're fast on the wrench. Good luck.
 

sloanstavern

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I think that’s the best next step, I’ll keep you posted- thanks
 

cruisermatt

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in my shop we ONLY bleed brakes with 2 person method.
 

sloanstavern

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Just finished a two man bleed- no joy ( zero bubbles at all).

I have one more option, not sure if it’s a good one or not, invest in a pressurized bleeder, pushes fluid from the wheel up to the resiv so gravity is on my side, in case there is an air pocket trapped in the line.

I was thinking through any other possible failure mechanisms, but none makes sense.

If the pedal pushrod was not extended properly then the pedal wouldn’t firm after pumping.

If the drums were too thin and over re-surfaced, then the wheels wouldn’t lock up.

If the shoes were too thin the wheels wouldn’t lock up. I’m running out of options
 
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Have you gravity blead it ? Clamped off the rear soft line to axle and see if pedal is good, that will isolate the issue to the rear brakes or front. FWIW when I had drums at all 4 I could get good pedal after adjusting the shoes with wheels bolted up tight, and vibrate the rear backing plates while its gravity bleeding, i open all 4 corners with water bottles and hoses on the bleeders and just let it flow, keep filling master.
 

Skreddy

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Did you ever set the pushrod height in the booster? If this is wrong, you can still get a firm pedal but won’t get full stroke if either too deep or too shallow. Then there’s also the pedal to booster length.
 

sloanstavern

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Did you ever set the pushrod height in the booster? If this is wrong, you can still get a firm pedal but won’t get full stroke if either too deep or too shallow. Then there’s also the pedal to booster length.
That’s what I’m leaning towards.
Given my symptoms ( too much travel) one or more of the push rods are too short ( do I have that right?)

Are three two rods?
One pedal to booster
Two- booster to master?
 

sloanstavern

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Have you gravity blead it ? Clamped off the rear soft line to axle and see if pedal is good, that will isolate the issue to the rear brakes or front. FWIW when I had drums at all 4 I could get good pedal after adjusting the shoes with wheels bolted up tight, and vibrate the rear backing plates while its gravity bleeding, i open all 4 corners with water bottles and hoses on the bleeders and just let it flow, keep filling master.
Thanks I’ll give it a shot
 

sloanstavern

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Have you gravity blead it ? Clamped off the rear soft line to axle and see if pedal is good, that will isolate the issue to the rear brakes or front. FWIW when I had drums at all 4 I could get good pedal after adjusting the shoes with wheels bolted up tight, and vibrate the rear backing plates while its gravity bleeding, i open all 4 corners with water bottles and hoses on the bleeders and just let it flow, keep filling master.
Great advice on isolating the circuits. When I blocked off the front circuit the rear was rockhard with no pedal travel at all what should be the case since I cranked out the shoes.

When I blocked off the rear circuit the front pedal went soft just as before at least now I know where to focus my attention thanks for the great tip
 
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Then leave the rears closed, gravity bleed the fronts all open at once, and use a palm sander up against the backing plate to vibrate/burp the wheel cyl.
2 rods, pedal to booster and booster to master. The booster to master you can take apart and measure, set correctly, the pedal end inside can be a pain to get to but if you can you want to not have free play. I don't remember if there is a pedal stop / height adjust other than the rod length, make sure the pedal is off the brake switch and see if there is free play. adjust to take that up. Also, while it is gravity bleeding and the res is full, slowly give it pedal, all the way, and slowly release while watching res to be sure its not low, it'll go fast with bleeders open. Let it up slow. Now while you are pressing down ( slowish) watch res, is fluid boiling back up in res as you push ? are bubbles coming in res as you push ? it should not burp or push fluid back into res. And as said previously, the shoes are going to seat so you have to set them , use them, and re adjust, adjust with wheels on, I had to run mine tight to where you could spin wheel but it had resistance, I run around block, yes they heat up, the sweet spot is tight enough to seat them in but not so thight you burn/glaze the shoes. It might take a few but you'll see the feel of pedal pick up as you go. Provided you sort the adjustment on the booster and pedal to eliminate that as an issue.
 

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