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Discussion Starter #1
Here is my situation,

69 Camaro front disc and rear drum, power

installed new power brake booster, master cylinder, metering block, proportioning valve and front hard and rubber lines.

i bench bled the master and bled all 4 wheels starting at the right rear, left rear, right front then left front.

during bleeding I got to the point where only fluid was coming out. Not my first time bleeding brakes.

At no one point did the pedal stop going to the floor.

If I hold something between the booster and the plunger on the back of the proportioning valve the pedal no longer goes to the floor.

Am I doing something wrong or did I get a bad master?
 

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naaaa, you just still have air in the back brake line that's all.

I ran 2 gallons of fluid (recycling it with a miti-vac bleeder) thru my new wilwood's before I got any kinda pedal at all. Still got some air in there somewheres, but at least the brakes work now.
 

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Discussion Starter #3
Jim, you know it's the back because? Is it the fact I mentioned about the holding the proportioning valve plunger and the pedal feels okay?
 

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Jim, you know it's the back because? Is it the fact I mentioned about the holding the proportioning valve plunger and the pedal feels okay?
It's in the back because that's the longest line. s'pose it could be in the front too tho.

Seriously, I bled mine FOREVER to get any kinda pedal at all. Sucked each wheel with the mitivac till it was time to refill the master, moved to the next one, around and around and around and around and around, for 4 days, thew first 2 of them 12 hour weekend days.

Didn't get any air out the last 2 days, but the pedal kept gettin better. Since then I've driven it a few times, briefly, pedal is still spongy, but keeps getting higher. Gonna bleed em again soon, probably run another gallon thru over the weekend.
 

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I tried Minivac on rears (new SS lines) and never could get it to pull the fluid all the way, ended up bleeding the rears using the conventional method, by pumping the brakes!
 

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if you clamp off the individual rubber lines, you will be able to tell which area has air in it. with rear hose clamped off, pedal is hard, then air is in rear, or vice versa for fronts...
 

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do NOT clamp the lines.. they aren't like rubber fuel lines that just spring back with no damage. they are steel reinforced.
i know they make a tool for that, but it's still not a good idea.
 

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Discussion Starter #8
Someone told me that when I bleed the brakes I should hold the proportioning valve plunger in(wedge something between booster and the boot on the back of the valve). Would this help?
 

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I "think" you only have to hold the prop valve plunger in when pressure bleeding rather than suction/pumping the pedal.

When you have replaced most/everything of the brake system, it takes a TON of bleeding to get all the air out.
 

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I've never had the problems you all are refering to. To properly bleed your brakes, start with the furthest from the master cylinder (rear right wheel) then progress to the closest and finish at the closest (front left wheel). Need someone else to pump the brakes for ya, power brakes need the engine running.
good luck.
also before bleeding the lines, bleed the master cylinder using the same pump up technique.
 

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If you hold the plunger, pedal no longer goes to floor....

Holding it all the way in is supposed to allow full flow to the front brakes.

It pushes all the way out when the brakes are applied and also has full flow.

If this plunger only moves partway, it blocks flow to the front brakes.
(this is why it needs held in when pressure bleeding. The amount of pressure in a typical pressure bleeder will only push it part way out). The purpose of this is to delay the front brakes from applying before the rear drums, but allows flow when at rest and normal braking pressure.

Sounds like when you hold it it is blocking flow to the front brakes, and you're getting a decent pedal because you only have the rear brakes moving.

That's how it breaks down logically to me, assuming the valve is the bullet shaped valve with the rubber boot, run in the front line off the master. That's the only one with a plunger anyway.

So, when you block off half the system you have a better pedal.

Did your booster and master come as a set? If not, I would check that the booster pushrod is the right length for your master cylinder. If it is too short it could cause this problem. Other than that, excessive movement (lining clearence, loose bearing, bent mount, stretched caliper, missing hardware) in the front brakes
or air.
or maybe a leak in that valve when not holding the plunger.
or
 

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Someone told me that when I bleed the brakes I should hold the proportioning valve plunger in(wedge something between booster and the boot on the back of the valve). Would this help?
Only hold in the plunger for pressure bleeding, the valve holds back pressure below aprox 50 psi, and pressure bleeders can't exceed 40 psi so the button was provided to open the valve and allow fluid to pass to the front calipers. I would remove the valve that has the plunger in it, and see if you have more success bleeding. The plunger seal can suck air in when bad. You don't really need the valve anyway if it's the separate round hold back valve.
David
 

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I know this is an old post but isn't there 2 holes for the plunger rod to the peddle one for drum one for discs?
 

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Yes top hole is for manual brakes and bottom hole is for power brakes.

Master cylinder mounted to fire wall is straight and aligns to the top hole on brake pedal.

Master cylinder mounted to booster at a upward angle and aligns to bottom hole on brake pedal.
 
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