brake system kickin my rear!

[rick spears]

i am working on a 73coupe 350 auto with power brakes. i bought this car recently, it had been sitting for quite awhile and it didn't run and barely had brakes to begin with. i got it running and i have been working on the brake system for about a week now. after inspecting it in the beginning, i noticed that both rear calipers had evidence of leaking, so i put 2 new calipers on. i tried to manually bleed it at this point, with no results. i borrowed a power bleeder, and bled the brakes again. i felt confident that i got all the air out of the system, but still just BARELY had a pedal. so i decided that the master cylinder was a problem. i installed a new master cylinder, (bench bled it) and manually bled the brakes again. i went around the car numerous times RR,LR,RF, and LF. STILL hardly a pedal at all. what am i over looking here? i have inspected all of the brake lines and connections, and see no leaks anywhere. one more thing.....what little pedal i do get after bleeding, goes to the FLOOR when i start the motor up...do i have a booster problem? would a bad booster prevent me from getting a pedal? after bleeding, i have just enough brakes to hold the wheels from turning while in drive at an idle.....HELP! PLEASE! any ideas anyone? rick

[mike cobine]

Re: brake system kickin my rear!

I don't want to insult you, but did you bleed all SIX bleeders? The rears have two each, inside and outside.

[Robert T.]

Re: brake system kickin my rear!

Rick,

Check the rubber hoses. Very often they deteriorate with age. Brake fluid gets between the layers of rubber and it causes them to swell and restrict the fluid flowing through them. Disconnect them from the calipers and press the pedal. You should get a heavy stream. You say that you have checked all the lines for leaks. The hoses can look fine but they have infact imploded.

Rob T.

[rick spears]

Re: brake system kickin my rear!

thanks guys...yes, i am aware of all 6 bleeders. i will check the rubber hoses on the front calipers. anyone else with any ideas??? rick

[Jim T.]

Re: brake system kickin my rear!

Replace those old brake hoses with new ones. Cheap maint replacement for safety.

[William C.]

Re: brake system kickin my rear!

Don't forget the rubber hoses on the rear either.

[Michael W.]

Re: brake system kickin my rear!

Is the red brake warning lamp on the dash illuminated? If so, the pressure differential switch may have blocked flow to the brakes you're trying to bleed.

[rick spears]

Re: brake system kickin my rear!

yes, the red brake light comes on as the pedal goes down. if this differential switch was blocked or bad, would that prevent me from gettin much of a pedal at all? this system really isn't that complicated....why can't i build any pressure?

[Michael W.]

Re: brake system kickin my rear!

I betcha that's it then. The switch is designed to deliberately block flow to the 'leaky' side of a faulty system.

There's lots of horror stories similar to this, most have been resolved with persistant applications of a pressure bleeder. I wish I had a magic solution for you.

[Patrick H.]

Re: brake system kickin my rear!

Mike,

Can't that switch be removed and cleaned out with denatured alcohol, pipe cleaners and judicious use of compressed air? I "assume" we're discussing the switch bolted to the frame just below and ahead of the master cylinder?

At least, I'll say that I did this when I took apart the system on Dad's 72.

Patrick

[Michael W.]

Re: brake system kickin my rear!

Sure you can clean the valve and it's a good thing to do, but the problem is the switch thinks it's doing it's job correctly. It's interpreting the difference in flow and pressure between the front and rear systems as a 'fault' and blocking the flow to the 'faulty' side as a result.

Later Sharks have always been a giant pain to bleed, there's lots in the archives on thesubject.

[Alan T.]

Re: brake system kickin my rear!

Guys, don't laugh at me, but recently I bled the brakes on my '69 and did not notice two bleeders on each of the rears. They pumped up and work just fine. Are there two bleeders on each of the rears for a '69 as well, meaning I missed two bleeders?

[Gary S.]

Re: brake system kickin my rear!

There should be.

[Steven E.]

Re: brake system kickin my rear!

I went thru this same problem last summer , lost the car for 2 months dealing with this...After gallons of brake fluid and hours of bleeding all the calipers, I replaced them with brand new castings w/o-ring pistons.. Also replaced all rubber hoses, pressure bleed system several times to be sure all the air was out..It worked for me , I know how your feeling about this, it drove me crazy trying to get a hard pedel...

[Harmon C.]

Re: brake system kickin my rear!

I usally have some problems with every brake job and am working on one right now that is just like yours. All new calipers,hoses,and master cylinder. It is power brakes also on a 73 and the light comes on when the pedal reaches the bottom. I am changing the calipers to another vendors parts to see if I get brakes. After that will be #2 new master cylinder. #3 will be drive it off a cliff!!!

Lyle