Bad power brake booster?

commando1 said:
Never once have I come across a person who got into an accident because they had drum brakes. Not once........
I can see it if you're towing a 32' Airstream through the Rockies.
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There it is ............ they arent as bad as they are made out to be.
 
Guys my problem is I can't get the brakes to lock up AT ALL... Like I said if I step on the brakes hard the pedal just becomes rock-solid. I've done some research and it seems like the internal diaphragm may be torn, making it leak once the pedal moves past a certain point. I know drum brakes aren't as good as discs only because they can't dissipate heat as well; they should be plenty strong in initial "bite" to lock up the wheels when tooling along at 20 mph which they aren't on this Polara.

I have driven disc-brake vehicles with this same problem, namely a 2001 Town & Country minivan with 4-wheel discs and even after replacing the pads and rotors it still had this issue where the pedal would just go solid once it got down to a certain point. Never did fix it but there's no other reason I can think of why that would happen. I also know this was not normal because we owned an '03 model of the exact same minivan and the brakes were MUCH stronger, no loss in assist no matter how far the pedal was pushed.
 
I go with your guess, you "override" the actual limit of the piston for brake actuation due to a bad internal seal and the front of the piston hits the housing. While I don't know the exact internals of your master, that's the way master cylinders are constructed to at least save function of the other circuit with a dual master cylinder. Some also have a small bore on the underside that leaks when overriding and the front circuit is concerned, while you have leakage on the end where the mc is attached to the booster with the circuit in the back. I'd disassemble the mc in that case to make sure and overhaul or replace it then.
 
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I would give it 100% inspection.....no need to replace parts that are still good. I would bleed the system one more time. If the problem is the same I would replace the booster.
 
You could have a lot of different things going on with that braking system. I've seen similar problems on newer cars caused by brake hoses failing internally, quite often brought on by a careless mechanic letting the calipers dangle on the brake hose.

I'd look at the power brake booster, first making sure I have good vacuum from the engine and working back from there.

As was suggested, going completely through the brake system is a pretty good plan.
 
My 2¢ on drum brakes.

A proper sized, well maintained drum brake will stop the car as good as a disc brake. There are advantages to disc brakes. They are resistant to fade caused by overheating and they do perform better when wet. Other than that, the disc brakes are cheaper to build and easier to maintain. You do have to replace them more often.

IMHO, most disc brake conversion claims are based on comparing a poorly operating, worn drum brake system and replacing it with new, properly operating disc brakes. Spend the time and money on fixing the drum brakes and expect the same results as disc brakes.

The limiting factor in braking is the tires. Once you lock the brakes, it doesn't matter what is locking them.
 
Thanks guys, I just placed a RockAuto order for a new power booster, wheel cylinders, brake lines, and front shoes. Should get here early next week, for the time being I'll continue on the front-end rebuild and starting to tear apart the top end of the engine for it to be pulled...
 
I just got home from the Power Tour. My car has power drum brakes all around. All total, I put 3120 miles on the car, in the rain, up and down mountains and a couple of quick, near-panic stops. I had zero trouble stopping the car. If the brake system is maintained and properly adjusted, it WILL WORK. I do plan to convert the master cylinder to dual-circuit, though, just for safety's sake.
 
It was a GREAT trip. We met so many really nice, friendly people (except for some of the Corvette guys. What's up with them, anyway?). We left Houston Saturday, June 1 and met the Tour in Arlington, TX. We rolled into Concord, NC at Z-Max Dragway Friday and finished the Tour on Saturday, June 8. I left Charlotte Sunday, the 9th and got home Wednesday, the 12th. I will admit the Tour was very tiring toward the end. The trip up and down Lookout Mountain, in Georgia, alone was rather harrowing, but still loads of fun. I made a few stops on the way home to visit friends in different states. I had done lots of pre-trip testing on the car and made sure it was ready for the trip. I had not one thing go wrong on the whole trip. It was wonderful and travelling in that big old 300 was so comfortable, I almost felt guilty and sorry for some of the guys in other, smaller uncomfortable cars. Almost. I am so glad I bought this car. And thanks to all you guys who answered questions for me and gave your great advice when I asked for it.
:yourock:
 
Excellent!! How many cars did they figure were on the tour? How many C bodies were there with you?
 
polara71 said:
Excellent!! How many cars did they figure were on the tour? How many C bodies were there with you?
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I was the only C-Body that I saw. I kept looking and looking. Saw lots of big Fords and Impalas, but no other Chryslers. When we pulled into Birmingham, the newspaper reported that they counted 4700 cars total, with 3500 Long Haul cars. I haven't seen anything official from Hot Rod yet, but they did say we broke the record by a long ways.
 
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