Power Brake Hell..... HELP!!!

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mrdodge69

mrdodge69

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Ok after chasing down a Crappy spongy brake pedal for too many years & spending Far to much $$$ I am at the end of my rope. It is the power brake set-up in my 69 Dart. Brake pedal is just a sponge, it has been bleed far to many times & there is NO air. I have changed & or replaced or rebuilt every part there is, & my latest purchase was the Willwood master in the pics. I can get the rear brakes to lock up long before the fronts ever will. As you can see in the pics the brake & clutch pedals are NO where near even, but I was told in the past this was "Normal" on P/B cars. Well I hate it as I have NO brake Pressure in the front. The New willwood is a 7/8" bore & a adjustable proportioning valve.

Should I loose the Booster & bolt the master direct to the firewall?

Moparfest is 2 weeks away & a 5 hour drive in a car with questionable brakes is not fun. I have done it to many years & NEED it Fixed!!!

HELP!!! Before it ends up in a new owner's garage.
 

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If a later model booster will fit with your engine, buy one and install it.
Its shorter in length than your dual diaphram but larger in diameter.
I'm assuming you have the 4 piston KH front disc system and it does take a lot of fluid volume to make fluid pressure there. Proportion valve is part of that equation also. In all of this is reasons they were changed.
Still...you do not want the front brakes to lock those wheels unless panic stop extreme pressure applied.
I'll never forget the first front disc brake car in the family. Uncle Charlie's 62 Bonneville. A panic stop tried through everyone through the windshield.
That is for example of every brand having faults in their early disc brake systems.
 
I had the factory 4 piston KH front disc system & switched to 4 piston SSBC calipers in the fall, No better, New proportioning valve, no better. Adjustable valve, no better. As you can see in the pics the brake pedal is very low to start. Is this normal with a P/B 4 spd car?
 
I just put a new booster and master cylinder on my Duster.When I went to bleed them the brake pedal was just a sponge.I found one of my front brake lines was leaking some although I tighten them down pretty firm and used locktight to seal the threads.I tighten the leaking line and it fixed the issue.My clutch pedal is below the brake pedal but now my brakes work awesome.

Jim
 
Ditch the booster. Go manual. That's a nice master. Just be done with it! More space under the hood and less weight, good pedal feel. Win win win....just finally ditched the power stuff on my duster and lovin it. It worked fine but a well set up manual brake car stops great and pedal feel is firm and consistent. Leave the power brakes to the mini vans and soccer mom SUV's that need 'em to compensate for lack of driving skills!
 
Sounds like you still have air in the system. Did you bench bleed the MC?

How old are the front brake lines?

Are the bleeder valves on the top or bottom of the calipers?
 
Sometimes it seems the more you spend money the further back you go. It all looks like very nice equipment.

That said, it shouldn't be spongy. My factory disc's will send you through the windshield easily.
 
I don't know why you think this is a "booster" problem?

Sounds like either air in the front lines, or a poor proportioning problem.

How EXACTLY did you bleed them?

Are the bleeders "on top" of the calipers?
 
TylerW said:
Sometimes it seems the more you spend money the further back you go. It all looks like very nice equipment.

That said, it shouldn't be spongy. My factory disc's will send you through the windshield easily.
Click to expand...

So will mine, non power discs. My wife's 73 Dart also has non power discs and they are very good.
 
I also did away with booster on my k.h. setup. No worries and stops much better. I used a newer master cylinder and saved weight in the process.
 
not sure by what you mean by "spongy".
-you can't lock the fronts no matter what, even with the peddle bottomed out, but not touching the floor?
-because the rears lock up first, (they will with a stock portioning valve), you've never gotten into the peddle far enough to lock the fronts?
-no matter how hard you push, the peddle keeps going down, the fronts never lock, and the floor is the only thing stopping it?

personally i hate power brakes on A-bodys. you might want to at least try it without the booster and see if it improves the feel.
also, like was stated, you need to do a propper bench bleed on the MS.

good luck

edit: the KH brakes work fine if everything is in good shape
 
Some times the flexible lines going to the calipers get old, and when you press the brake pedal instead of transferring the pressure the hose will expand like a balloon.
 
Are you sure that is a disc booster? It should look like this inside (pic)
 

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If not then it is a drum brake booster and that may be the problem
 
Beatnik said:
Ditch the booster. Go manual. That's a nice master. Just be done with it! More space under the hood and less weight, good pedal feel. Win win win...
Click to expand...

I agree man. Just go manual. Saves alot of headaches. I like the pedal feel of manual brakes, some people do not, however. :)
 
Is the M/C bore diameter correct? Seems like it should be larger to move more volume. As far as how low the pedal is, Is there any adjustment on the pedal push rod?
 
RedFish said:
I'll never forget the first front disc brake car in the family. Uncle Charlie's 62 Bonneville. A panic stop tried through everyone through the windshield.
That is for example of every brand having faults in their early disc brake systems.
Click to expand...

Uncle Charlies Bonneville sounds a lot like the only new GM truck my Dad ever bought for his business, a 1970 GMC 3/4 Ton. If I remember right it hydroboost brakes on it. Everybody that ever drove that thing complained about the brakes. I think if it were not for the gutter machine and rolls of gutter coil in the bed the thing would have stood on the front bumper.

I have not had an A-body with power brakes, ever. But the pedal does not seem right.....
 
The pedal height issue would probably be in the booster linkage or in the master pushrod length.

Spongy pedal is 99% of the time air in the lines. as noted in a previous post master cylinder bore diameter will effect pedal pressure so you could have got the wrong size. I also think rear brakes WAY out of adjustment will cause a spongy pedal.

I wen't from power to manual brakes and I liked it. FWIW
 
Well there no air in the entire system. Went from a 1 1/32 master cylinder to a 7/8 Wilwood with a adjustable prop. valve & still not a good peddle. Was wondering if I may have the wrong pedal linkage to the booster. It is a Dual diaphragm booster & looks to be peddle assy. from a 73 vintage (as it has the curved brake pedal) so could it be the Wrong peddle assy?? Or do I just Sell the Booster & go back to manual to get that Rock hard peddle I am after???

Thanks for all the info & assistance guys... FABO is the Best..

2 Weeks To MOPARFEST!!!!!!!!!!!
 
just a quick thought, if the rear brakes lock before the front, are you sure that the lines aren't installed backwards on the master cylinder?

the rear reservoir should feed the front brakes and front reservoir feed the rear
 
66plyValiant said:
just a quick thought, if the rear brakes lock before the front, are you sure that the lines aren't installed backwards on the master cylinder?

the rear reservoir should feed the front brakes and front reservoir feed the rear
Click to expand...

Checked that as well. Thought the same thing. But Thanks
 
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