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Power Drum Brakes: Pedal Goes to Floor? #2453305
02/18/18 01:24 AM
02/18/18 01:24 AM
Joined: Jan 2003
Posts: 1,177
People's Republic of Kali
70runner Offline OP
super stock
70runner  Offline OP
super stock

Joined: Jan 2003
Posts: 1,177
People's Republic of Kali
69 Charger RT, new MC and stock booster/prop valve, replaced front lines during engine rebuild. Bench bled MC, then bled RR, LR, RF, LF several times until no air bubbles (Dot4). Pedal good until engine start at which point pedal goes to floor. Stock engine rebuild so plenty of vacuum for booster.

Did it again, incl bench bleed, same result. No leaks apparent, new wheel cylinders. Would seem to be booster related as that is the only brake sys component activated at startup, although IIRC a bad booster typically causes a hard pedal.

Suggestions?

Re: Power Drum Brakes: Pedal Goes to Floor? [Re: 70runner] #2453308
02/18/18 01:33 AM
02/18/18 01:33 AM
Joined: Mar 2003
Posts: 5,193
NEW JERSEY
AARCONV Offline
master
AARCONV  Offline
master

Joined: Mar 2003
Posts: 5,193
NEW JERSEY
Bled to no air bubbles..but was the pedal hard and steady?

Re: Power Drum Brakes: Pedal Goes to Floor? [Re: 70runner] #2453320
02/18/18 02:03 AM
02/18/18 02:03 AM
Joined: Jan 2003
Posts: 1,177
People's Republic of Kali
70runner Offline OP
super stock
70runner  Offline OP
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Posts: 1,177
People's Republic of Kali
Yes, after bleeding, pedal was hard and steady...until I start the engine.

Re: Power Drum Brakes: Pedal Goes to Floor? [Re: 70runner] #2453321
02/18/18 02:04 AM
02/18/18 02:04 AM
Joined: Dec 2007
Posts: 18,153
Mass
DAYCLONA Offline
I Live Here
DAYCLONA  Offline
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Posts: 18,153
Mass
air gap between master and booster?, should be .020 to .060 max, too much and pedal goes to the floor...

booster gap.JPGbooster5.JPGbrake-adjuster.jpg
Re: Power Drum Brakes: Pedal Goes to Floor? [Re: 70runner] #2453330
02/18/18 02:26 AM
02/18/18 02:26 AM
Joined: Jan 2003
Posts: 1,177
People's Republic of Kali
70runner Offline OP
super stock
70runner  Offline OP
super stock

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Posts: 1,177
People's Republic of Kali
I'll check it out, THX!

Re: Power Drum Brakes: Pedal Goes to Floor? [Re: 70runner] #2453332
02/18/18 02:31 AM
02/18/18 02:31 AM
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert Offline
Circle Track
Happy Birthday RapidRobert  Offline
Circle Track

Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
an engine valvetrain pushrod makes an easy tool to measure the distance out to the MC flange then you want the booster pushrod .020" less than that distance protruding out from the booster flange.


live every 24 hour block of time like it's your last day on earth
Re: Power Drum Brakes: Pedal Goes to Floor? [Re: RapidRobert] #2453362
02/18/18 04:34 AM
02/18/18 04:34 AM
Joined: Jun 2004
Posts: 3,319
Chicago Burbs
sthemi Offline
master
sthemi  Offline
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Posts: 3,319
Chicago Burbs
if you make the pushrod too long, brakes will be applied anytime the engine starts







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