Front Brakes Locked

[markbob]

Hello All....

I was out cruising in my 69 Coronet 2 door....with all drum brakes....

I noticed that the car would not coast when I released pressure on the gas pedal....

I jacked the car up and the front wheels would not turn....

I opened up the passenger side wheel brake bleeder and let a bit of fluid out....and now both wheels turn....

I replaced the master cylinder and all of the wheel cylinders during the restoration....when doing this, I could not get any fluid to the rear brakes....so I elongated the adjustable plunger on the brake booster....after this was done, I was able to bleed the rear brakes....

any thoughts?

thank you very much,

Mark

 

[Cranky]

How old are the flexible lines? Kinda unusual for both to be messed up tho but it could happen...

 

[markbob]

Cranky,

I replaced all the lines.....solid ones are SS.......the flexible ones are brand new as well....

BTW.....I love the pix of Clint under your name....one of my all time fav movie scenes...

thanks again,

Mark

 

[brasil]

..I would go for the MC ! or the pushrod that goes inside the MC from the booster. if the MC is a new one....sometimes you have to adjsut the pushrod. Had the same issue when I did my brakes.... to check the pushrod lenght I put my car on a lift... turned the front wheels.... they stucked... then I opened the scews that attach the MC to the booster.... to get more "freeplay" ...and the wheels were able to be turned... So I knew what to do.... shortend the pushrod a little... DONE !

 

[wedge69]

X2 ! Check you pushrod lenght. You need alittle Play/ stroke before it applys pressuer. If none is there the master cylender will not come back enough to release the fluid .

 

[markbob]

X2 ! Check you pushrod lenght. You need alittle Play/ stroke before it applys pressuer. If none is there the master cylender will not come back enough to release the fluid .

I opened bleeder and adjusted pushrod length

I drove car yesterday and today and after a 100 miles or so
the front wheels are locked again

what do u think my next step is?

 

[5.7 hemi]

At this point, I would change the front rubber lines.

 

[bm02tj]

before changing any thing when brakes are tight loosen the line at the master and then next one down the line till you find the point that is holding the brake pressure

and as posted earlier loosen bolts on master to allow more room for push rod

good luck

 

[markbob]

Thanks for replies....

I will loosen the master bolts again and see if the pressure releases tomorrow....

I am curiuous why it takes so long for this condition to develop....even if the plunger is a bit overadjusted, wouldn't it cause the brakes to lock immediately?

additionally, at some point, I won't have enough plunger action to activate the rear brakes....this is why the plunger was adjusted in the first place....

what is the function of the vacuum hose on the booster? could this be a source of the problem?

thanks,

Mark

 

[bm02tj]

after every thing warms up the fluid expands and will hold the brakes on if plunger does not travel far enough bace to open the port to release fluid
and if piston does not travel back far enough the port to let fluid in will not let you bleed rear brakes

remove vacuum hose and plug to eliminate the booster for test

 

[5.7 hemi]

The booster just makes it easier to apply the brakes, no more, no less.