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  #1 (permalink)  
Old 05-19-2008, 05:10 PM
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Disc/Drum Brakes, no rear

I have been through this before and thought I had it all set and left the brakes alone while working on the rest of the car.
It's a street rod with MII front calipers and chevy rear drums.
Everything is new.
Front calipers work fine when rear line is disconnected and port on MC is plugged.
Under floorboard MC with 10lb. residual and proportioning valve.
Had the pedal up and working fine prior to leaving car sitting for a while.
Now the pedal goes right to the floor.
I can pump them up and get a pedal.
Is this just air in the line?
I have bled and bled the 2 person way.Pump and bleed.
I have bled the MC and the pro. valve.
I will bleed it all again.
I have read ALL the threads on brakes and have never seen where anyone comes back and post the final positive result!
Or maybe I just missed that.
I have a manual MC for a 73 Pinto/74 MII and 73 Nova rear brake cylinders.
IS IT JUST AIR?

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Old 05-20-2008, 01:14 AM
aka Duke of URL
 
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If you have an under the floor board MC installation, you must use 2# residual valves front and rear to keep the fluid from draining back to the MC.
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Old 05-20-2008, 03:33 AM
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Quote:
Originally Posted by KULTULZ
If you have an under the floor board MC installation, you must use 2# residual valves front and rear to keep the fluid from draining back to the MC.
2#(with disc) on the frt,10# on the rear (with drum brakes)
should take care if your problem...
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Old 05-20-2008, 05:03 AM
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I wish that was the problem.
I have a 2# on the front and a 10# on the rear.
Facing the correct way and mounted close to the MC.
Any suggestions greatly appreciated.
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Old 05-20-2008, 05:26 AM
F&J F&J is offline
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Quote:
I can pump them up and get a pedal.
Get someone to go around and try to spin each wheel. Hopefully, you can isolate where the problem is.

"IF" is was a stock vehicle, the symtoms indicate a "saftey valve" in the proportionong valve assembly is "blocking" you from bleeding out the rear lines. What type of P-valve?...and does it have some sort of "pin" that needs to be held "in" while bleeding?...or the type of valve that needs the brake warning switch removed, and a temporary bolt installed to hold the safety valve? (while bleeding)
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Old 05-20-2008, 06:08 AM
aka Duke of URL
 
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Quote:
Originally Posted by tomslik

2#(with disc) on the frt,10# on the rear (with drum brakes)
should take care if your problem...
Correct. 2# is for disc only. I will be OK.

Quote:
Originally Posted by Cape Cod Bob

I have been through this before and thought I had it all set and left the brakes alone while working on the rest of the car.

It's a street rod with MII front calipers and chevy rear drums.

Everything is new.

Front calipers work fine when rear line is disconnected and port on MC is plugged.

Under floorboard MC with 10lb. residual and proportioning valve (You also mentioned 2# residual valve on front circuit- correct?).

Had the pedal up and working fine prior to leaving car sitting for a while.

Now the pedal goes right to the floor. I can pump them up and get a pedal.

Is this just air in the line?

I have bled and bled the 2 person way.Pump and bleed. I have bled the MC and the pro. valve. I will bleed it all again.

I have read ALL the threads on brakes and have never seen where anyone comes back and post the final positive result!
Or maybe I just missed that.

I have a manual MC for a 73 Pinto/74 MII and 73 Nova rear brake cylinders.

IS IT JUST AIR?
OK. Let's start over again.

You have a disc/drum system?

You have a disc/drum master cylinder?

You have a 2# front residual valve and a 10# rear residual valve?

You mentioned a proportioning valve. Is this free standing or is it part of a combination valve (metering-pressure differential-proportioning)?

The front calipers-were the bleeders standing straight up while bleeding (you may have to rotate calipers housing slighly to achieve this)?

Are the rear shoes adjusted correctly and centered tightly against the drum(s)?

Is the MC pushrod adjusted correctly?

It sounds like air in the system if you can pump a few times and get a pedal. The MC is new and no internal leaks?
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Old 05-20-2008, 02:19 PM
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OK. Let's start over again.

YES,GOOD IDEA.

You have a disc/drum system?
YES
You have a disc/drum master cylinder?
YES
You have a 2# front residual valve and a 10# rear residual valve?
YES
You mentioned a proportioning valve. Is this free standing or is it part of a combination valve (metering-pressure differential-proportioning)?
FREE STANDING PROPORTIONING VALVE PROPERLY BLED
The front calipers-were the bleeders standing straight up while bleeding (you may have to rotate calipers housing slighly to achieve this)?
THEY ARE AT THE TOP OF THE CALIPER. THE FRONT BRAKES WORK GREAT WHEN REAR LINE IS DISCONNECTED AND PLUGGED
Are the rear shoes adjusted correctly and centered tightly against the drum(s)?
THE REAR SHOES ARE ADJUSTED UP SO I CAN TURN THE WHEEL BY HAND BUT NOT SPIN
Is the MC pushrod adjusted correctly?
YES, ACCORDING TO ALL THE TECHS I'VE READ
It sounds like air in the system if you can pump a few times and get a pedal. The MC is new and no internal leaks?
YES ,NEW AND NO LEAKS.

i HAVE BLED THE REAR BRAKES AGAIN AND EVEN THOUGH I HEAR NO AIR ESCAPING I NOW HAVE A PEDAL.
WHAT I AM WONDERING IS WHILE THE CAR SITS IDLE FOR A LONG TIME ,WHY ARE THE REAR BRAKES LOSING PRESSURE.
COULD I HAVE AN AIR LEAK INTO THE LINE?
I WILL NOW HAVE THE URGE TO TRY THE BRAKES EVRERY TIME I GO BY THE CAR.
I WANYT TO WAIT AT LEAST A WEEK ,THEN TRY THEM.
THANKS FOR THE HELP AND WILL KEEP POSTED
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Old 05-20-2008, 04:08 PM
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I would take a peek at everything for leaks also. It doesnt take much air to make the pedal very spongy. Are you having to add any fluid other that what you use when you bleed them.

Chet
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Old 05-20-2008, 04:15 PM
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Chet, that's the thing I don't understand. There is no fluid except what I bleed out.
I will just have to wait and see how long it holds this pedal.
I plan to check in 2, then 4,8 etc. days and have a better idea what is happening.
The car is not readt to run yet.
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Old 05-20-2008, 05:23 PM
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Quote:
Originally Posted by Cape Cod Bob
Chet, that's the thing I don't understand. There is no fluid except what I bleed out.
I will just have to wait and see how long it holds this pedal.
I plan to check in 2, then 4,8 etc. days and have a better idea what is happening.
The car is not readt to run yet.
ok, your original post didn't say you had a valve in the front lines....
next thing would be to block off the front brake line and see if you still have the same prob.
if so, the m/c be bad (or the issue is in the rear.)
(do the same one the rear and see if the prob goes away)
if not,the valve is bad


this is assuming the system is bled and not leaking.



i'm not real good at trying to say this on the 'net so i hope it's clear enough
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  #11 (permalink)  
Old 05-20-2008, 05:48 PM
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thanks tom, will do that tomorrow.
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Old 06-05-2008, 09:38 PM
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Well I waited till todaay to try the brakes and I still have a pedal so. I guess it was just not bled all out.
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Old 06-06-2008, 07:31 AM
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I'm getting in on this thread late but I do have a question. Why would you need a 2# proportioning valve on the front when the master cylinder is set up for disc front already? When I installed the disc's on the front of my car I went by the street rodders manual and all it indicated was that I needed a proportioning valve for the rear drums.

I installed a MC off of a smaller Japanese unit that was orginally for disc on both front and rear. As with most 32's I installed it under the car. My system works perfectly after getting the adjustment on the proportioning valve set correctly.

There is no bleed back off of the front units and my pedal has always been good.

Steve
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Old 06-06-2008, 01:51 PM
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All I know(and that ain't much) is all the brake guros say we need a 2# residual valve to keep pressure on the front discs to protect against bleed back and therefor keeping the pedal up and not allowing the brake fluid to overflow the MC when thw MC is mounted lower then the brake cylinders?
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Old 06-06-2008, 01:58 PM
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sometimes, it will drain back from gravity, if it does, then you need the 2# valve, if it does not, then your good.. if you have drums in the rear, you should have a 10# valve tho. holds the shoe out and will give a better pedal and brakes will react faster
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