*sigh*...when will it end. "Brake question and troubles

[MYRIDE]

Ok rodders....
New MP Brake system (under floor)
New 11" Disc/rotor system up front
Rebuilt (completely) 10x2.5" drums in rear
New lines, proportioning (combination)valve, 2 & 10 lbs residual valves.

LOTS of front end pressure, NO preassure for the rear. Pedal is firm and then gets spongier the more I use it. Have bled and bled and bled the system. Checked M/C, proportioning valve and seem to have lots of flow on the other side of my residual (10 lb.

My question (finally)"could" my residual NOT be holding 10 lbs pressure inline and alowing the system to "bleed back"?
This has me so pi**ed I threw the tires back on and took her for a midnight ride around the neihborhood last night (much to my neighbors chagrin!)

HELP!!!

[enjenjo]

The easiest way to check the valves, clamp the rubber lines shut, and press on the pedal. If the pedal is high and hard, the valve is defective. It could be either valve, front or rear.

I just had a similar problem on a car we are working on, it turned out the pushrod from the booster to the pedal, and the one from the booster to the master cylinder were both too long. The front brakes worked good, the rears were ineffective. After adjusting the rods, it worked fine.

[MYRIDE]

The easiest way to check the valves, clamp the rubber lines shut, and press on the pedal. If the pedal is high and hard, the valve is defective. It could be either valve, front or rear.

I just had a similar problem on a car we are working on, it turned out the pushrod from the booster to the pedal, and the one from the booster to the master cylinder were both too long. The front brakes worked good, the rears were ineffective. After adjusting the rods, it worked fine.

Enjenjo, thanks I'll try adjusting the rods this evening, I have adjusted them "out" thinking they were to short....maybe I should shorten them up a little.
Ken

[Kctom]

Ok rodders....
New MP Brake system (under floor)
New 11" Disc/rotor system up front
Rebuilt (completely) 10x2.5" drums in rear
New lines, proportioning (combination)valve, 2 & 10 lbs residual valves.

LOTS of front end pressure, NO preassure for the rear. Pedal is firm and then gets spongier the more I use it. Have bled and bled and bled the system. Checked M/C, proportioning valve and seem to have lots of flow on the other side of my residual (10 lb.

My question (finally)"could" my residual NOT be holding 10 lbs pressure inline and alowing the system to "bleed back"?
This has me so pi**ed I threw the tires back on and took her for a midnight ride around the neihborhood last night (much to my neighbors chagrin!)
If you have one of the combination valves installed. both lines from the master cylinder go to it and then 2 come out for the front brakes and one for the rear. There is a shuttle valve inside. It is to shut off the fluid supply should a line brake . On the top of this valve is a little plug for a wire. I use to think it was to let you know when the fluid was low. Not the case it is to light up a light to show part of the system has a problem.  When ever you bleed your brakes put a test light or meter on the center stud on the switch. This switch will groud if a problem is there. The light or meter will show this. Master Power Brake web site shows how to correct this problem. It is possible not to have brakes on the front or the rear and never know it. Always check this after you  bleed the brakes. Don't need to hold the pedal down just use you test light or meter. I learned the hard way
HELP!!!

[phat rat]

Ok rodders....
New MP Brake system (under floor)
New 11" Disc/rotor system up front
Rebuilt (completely) 10x2.5" drums in rear
New lines, proportioning (combination)valve, 2 & 10 lbs residual valves.

LOTS of front end pressure, NO preassure for the rear. Pedal is firm and then gets spongier the more I use it. Have bled and bled and bled the system. Checked M/C, proportioning valve and seem to have lots of flow on the other side of my residual (10 lb.

My question (finally)"could" my residual NOT be holding 10 lbs pressure inline and alowing the system to "bleed back"?
This has me so pi**ed I threw the tires back on and took her for a midnight ride around the neihborhood last night (much to my neighbors chagrin!)

HELP!!!

The other guys have given you good answers. But I had an experience with MPB that soured me on their parts. I wouldn't use their stuff on a kids little red wagon.

[SKR8PN]

I have to agree with Phat Rat. MPB's customer service SUCKS.......And all I bought from them was a universal pedal assy and a master cylinder/booster set-up......I would check the push rod length first, THEN your proportioning valves in the rear.

[phat rat]

I have to agree with Phat Rat. MPB's customer service SUCKS.......And all I bought from them was a universal pedal assy and a master cylinder/booster set-up......I would check the push rod length first, THEN your proportioning valves in the rear.

My booster was bad out of the box took almost a year to figure it out. Was chasing every thing else, then they finally said to send it back for them to check. Got a new one back and it wouldn't work much better, they claim you need 18 lbs of vacumn to make it work right, I had 15 1/2-16. I went down to the parts yard and pulled one off an Astro van paid $10 and it works great. So much for their  $250 booster, I got rid of it at a loss and siad I'd never buy anything of theirs again. Plus I'm not shy aboput telling other people about what I think of their parts

[enjenjo]

I have to agree with Phat Rat. MPB's customer service SUCKS.......And all I bought from them was a universal pedal assy and a master cylinder/booster set-up......I would check the push rod length first, THEN your proportioning valves in the rear.

My booster was bad out of the box took almost a year to figure it out. Was chasing every thing else, then they finally said to send it back for them to check. Got a new one back and it wouldn't work much better, they claim you need 18 lbs of vacumn to make it work right, I had 15 1/2-16. I went down to the parts yard and pulled one off an Astro van paid $10 and it works great. So much for their  $250 booster, I got rid of it at a loss and siad I'd never buy anything of theirs again. Plus I'm not shy aboput telling other people about what I think of their parts

Not necessarily in defense of MPB, the failure rate on the 7" street rod boosters seems a bit high, regardless of the vendor. I have seen bad ones out of the box from different sources. My guess, there is one, possibly two manufacturers that make most of them. This is based on comparing the ones from different sources.

This is one of the reasons I tend to use OE parts in the brakes.

PS, I just replaced a 7" booster that failed at less than 5,000 miles.

[phat rat]

I have to agree with Phat Rat. MPB's customer service SUCKS.......And all I bought from them was a universal pedal assy and a master cylinder/booster set-up......I would check the push rod length first, THEN your proportioning valves in the rear.

My booster was bad out of the box took almost a year to figure it out. Was chasing every thing else, then they finally said to send it back for them to check. Got a new one back and it wouldn't work much better, they claim you need 18 lbs of vacumn to make it work right, I had 15 1/2-16. I went down to the parts yard and pulled one off an Astro van paid $10 and it works great. So much for their  $250 booster, I got rid of it at a loss and siad I'd never buy anything of theirs again. Plus I'm not shy aboput telling other people about what I think of their parts

Not necessarily in defense of MPB, the failure rate on the 7" street rod boosters seems a bit high, regardless of the vendor. I have seen bad ones out of the box from different sources. My guess, there is one, possibly two manufacturers that make most of them. This is based on comparing the ones from different sources.

This is one of the reasons I tend to use OE parts in the brakes.

PS, I just replaced a 7" booster that failed at less than 5,000 miles.

Frank, mine was an 8" dual diaphram, they were the only ones at the time who had one. I can't begain to remember how many times I talked to them in that years time. It was always the same story, had to be my set-up. Well in that years time I changed the car over from 4 whl drums to 4 whl disc so everything but the booster had been changed still no difference in the way it stopped (or didn't). One time I happened to get the owner and he said to send the booster and master back and they'd check it out. That's when I finally found for sure it wasa bad booster. When I got it back and it wasn't much better I said to hell with their booster and bought the used one which works great.

[Ed ke6bnl]

I hope I am not really changing the topic but I have been bothered by a brake problem since I got my 50 F1 on the road, mustang II, 9" rear with drum brakes, proportional valve, 2 and 10 psi residuals, an a power brake under the floor,  The brakes work and are solid, even broke a rear brake line and the fronts worked till I repaired it.  The problem is it does not feel like I have power brakes, I have vacuum from the rear of the intake manifold. What test or advice do you recommend for me to test and resolve this on going problem Ed ke6bnl

[GUS]

Ok rodders....
New MP Brake system (under floor)
New 11" Disc/rotor system up front
Rebuilt (completely) 10x2.5" drums in rear
New lines, proportioning (combination)valve, 2 & 10 lbs residual valves.

LOTS of front end pressure, NO preassure for the rear. Pedal is firm and then gets spongier the more I use it. Have bled and bled and bled the system. Checked M/C, proportioning valve and seem to have lots of flow on the other side of my residual (10 lb.

My question (finally)"could" my residual NOT be holding 10 lbs pressure inline and alowing the system to "bleed back"?
This has me so pi**ed I threw the tires back on and took her for a midnight ride around the neihborhood last night (much to my neighbors chagrin!)

HELP!!!

Hi, new to the board here but I thought I would throw in my 2 cents. The 10lb valve is nothing but a one way check valve.  It will not cause spongy brakes. I am assuming you are starting with a fresh system.  Your problem is loosing pressure right? How did you check the master? If you put your foot on the brake and it falls under your foot to the floor, it is by passing in the M/C.

[enjenjo]

I hope I am not really changing the topic but I have been bothered by a brake problem since I got my 50 F1 on the road, mustang II, 9" rear with drum brakes, proportional valve, 2 and 10 psi residuals, an a power brake under the floor,  The brakes work and are solid, even broke a rear brake line and the fronts worked till I repaired it.  The problem is it does not feel like I have power brakes, I have vacuum from the rear of the intake manifold. What test or advice do you recommend for me to test and resolve this on going problem Ed ke6bnl

Which booster?

[GUS]

I hope I am not really changing the topic but I have been bothered by a brake problem since I got my 50 F1 on the road, mustang II, 9" rear with drum brakes, proportional valve, 2 and 10 psi residuals, an a power brake under the floor,  The brakes work and are solid, even broke a rear brake line and the fronts worked till I repaired it.  The problem is it does not feel like I have power brakes, I have vacuum from the rear of the intake manifold. What test or advice do you recommend for me to test and resolve this on going problem Ed ke6bnl

Rule of thumb is 18 inches of vacuum at an engine idle at the booster.

[C9]

I hope I am not really changing the topic but I have been bothered by a brake problem since I got my 50 F1 on the road, mustang II, 9" rear with drum brakes, proportional valve, 2 and 10 psi residuals, an a power brake under the floor,  The brakes work and are solid, even broke a rear brake line and the fronts worked till I repaired it.  The problem is it does not feel like I have power brakes, I have vacuum from the rear of the intake manifold. What test or advice do you recommend for me to test and resolve this on going problem Ed ke6bnl

Any chance you have the vacuum sourced to a thermal vacuum switch?
Thermal vacuum switches look very much like a vertical vacuum block (like in fuel block) but some of the bibs don't get vacuum until the engine is way hot.

[MYRIDE]

Update.....
Checked preassure frome M/C....good.
Checked preassure from Combination Valve.......also great
Checked preassure from Residual Valve ("out" end) great...BUT, noticed a little "suction when the pedal was released. Seems the fitting I had used was a tad to long, this inturn kept the "plunger-like" white valve inside open all the time.
Changed fitting.....re-bled lines, "better pedal but still not great. The rear drums grab but only enough to "slow the hubs.....not stop them completely. I'm hoping we're down to a further bleeding and adjusting problem now. "I Hope"!

Kctom1, I'm headed to MP brakes site now. Will update tomorrow once I've checked the combination valve "switch"
Thanks, K