Good pedal til car is running

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evil 340

evil 340

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72 demon
73 power disc front/drum rears
All new lines. New prop valve
Reman master (bench bled)and booster/booster holds vacuum when car is shut down and u pull check valve it lets out air
Check valve works one way
Good fluid to all 4 corners.
Decent pressure when not running, but as soon as it starts .....straight to the floor


POINT ME TO THE PROBLEM please. Thanks in advance
 
Any change in engine RPM? Decent pressure means?
 
Pretty good. Could be a little tighter in my opinion. But maybe its cause i m a sasquatch. Tiny bit softer than manual 4 wheel drums
 
If it goes soft with no RPM change then it sound like air is still in the system. Are the bleeders oriented correctly? Did you try bleeding while running?
 
When you say straight to the floor. Does that mean straight to the floor and no brakes? Or straight to the floor but it still stops?
 
If all that checks, was this a power upgrade and did you measure the push rod length on the booster?
 
Bench bleed and make sure all air is out of everything. Just went through this with a pick up truck.
 
Straight to the floor.lustle
This is upgrade. Original manual drums.both bleeders on top up front. Have not tried bleeding while running. Pushrod gap is less than 1/8"
Maybe i should start fresh. Bench bleed the master again and try bleeding again. I ll double check gap.
DOOGIEVIG. Does this sound exactly like the same scenario as your truck issue? Pedal til its running then nothing.??
 
evil 340 said:
Straight to the floor.lustle
This is upgrade. Original manual drums.both bleeders on top up front. Have not tried bleeding while running. Pushrod gap is less than 1/8"
Maybe i should start fresh. Bench bleed the master again and try bleeding again. I ll double check gap.
DOOGIEVIG. Does this sound exactly like the same scenario as your truck issue? Pedal til its running then nothing.??
Click to expand...

Yes.
 
The pedal and pushrod are different from manual to power. The hole the pushrod connects to is in a slightly different place and the pushrod is a different length. An adjustable pushrod might be in your future. If you had the whole system open it usually takes a while to get the air out. I usually gravity bleed them.
 
evil 340 said:
72 demon
73 power disc front/drum rears
All new lines. New prop valve
Reman master (bench bled)and booster/booster holds vacuum when car is shut down and u pull check valve it lets out air
Check valve works one way
Good fluid to all 4 corners.
Decent pressure when not running, but as soon as it starts .....straight to the floor


POINT ME TO THE PROBLEM please. Thanks in advance
Click to expand...
Ran into this before my problem was the calipers were on the wrong side the bleed screws were on top but there was a small void, and not letting all the air out.Switched calipers around and the bleed screws were at the very top.Bled and problem solved.
 
GeorgeH said:
The pedal and pushrod are different from manual to power. The hole the pushrod connects to is in a slightly different place and the pushrod is a different length. An adjustable pushrod might be in your future. If you had the whole system open it usually takes a while to get the air out. I usually gravity bleed them.
Click to expand...


Good solutions above.

When I said pushrod I mean the booster rod itself as is has a pre-determined lentgh according to the manual.
 
Thanks for all the advice guys, i just haven t had time to mess with it yet. The master is for a 73 power brake car. The booster is a reman 73 unit. So i m guessing the rod in the booster would be the correct one. But there is obviously something wrong so thanks for all advice. I wish i had a 73 manual book. I have 71 and 72 but they re pretty useless since its a completely different system
 
I ll post some pics of what i m workin with tomorrow and see if anyone can spot something obvious and out of order. This is my first disc conversion
 
Pic 1

20170622_071051.jpg
 
Well i finally found time to work on it. I bought a new master cylinder just because it was not that expensive and i m gonna use the same style on my 71. At this point the new master is on. The pedal felt pretty good when i bench bled the master on the car. Everything felt good. Soon as i hooked it up to lines and bled it felt a bit softer. Then once i fired it.......Everything s the same. Super soft almost to the floor. No pedal basically. But the brakes work.
 
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