68 Barracuda power drum brakes,peddle hard.

-
pettybludart

pettybludart

Well-Known Member
Joined
Jul 18, 2008
Messages
15,311
Reaction score
289
Location
Ontario,Canada
I have a newly aquired 68 Barracuda fastback with 318,A/C, p.steering and power drum brakes.Everything is new on the brakes.Drums,shoes,hoses.I noticed when stopping the car it seems like there,s no power?It,s been years since I,ve driven a car with power drum brakes,but these don,t seem like power brakes to me.Maybe I need to do a 4 wheel bleed of the system,but can,t see why this wasn,t done when the new parts where installed.Is it just me or is it normal for these to feel hard?My 66 Dart with manual disc stops way better.

Oh and the booster is fine,holds air fine.

Any input will be appreaciated.Thanks
 
This can be all over the place. Start engine to get vacuum, then shut off. Now push pedal several times; if the pedal raises, compared to engine running- booster. What size bore is the M/C? It seems backward, but a bigger bore means more pressure to stop.
 
green1 said:
This can be all over the place. Start engine to get vacuum, then shut off. Now push pedal several times; if the pedal raises, compared to engine running- booster. What size bore is the M/C? It seems backward, but a bigger bore means more pressure to stop.
Click to expand...

2cne440.jpg


If the booster is working, after you shut off the engine, you should immediately tell the difference in pedal after one or two footstrokes

Also, there is a HUGE bunch 'o stuff that can detract drum brakes. If someone turned the drums a little too large, the shoes will only contact the center area of the braking surface, meaning only a part of the shoes are doing the work. This makes them overheat, glaze and you need more pedal to stop

Shoes come in a few different "quality" so pedal pressure and evident braking can be very different between shoe types.

Someone may have switched the primary / secondary shoes front to rear, which will affect braking.

And, of course, drums are affected simply by how large they are. In this day and age, we've become used to lighter cars with disk--and four wheel disk brakes. Many of these old girls never were stellar in the braking dept.
 
Is'nt the smaller the cylinder the greater the pressure/less volume, Bigger the cylinder more volume/less pressure?

You should "feel" the assistance of the vacuume when pressing the brake pedal engine on! Could also be that the shoes are in the wrong place, Two sizes on each wheel! primary "shorter" one goes in front and larger one goes in the rear. When facing the wheel look at the shoes should have one short towards the front of car, and one long towards the back of car, there is a difference! Ask me how I know? Anyway I would look at that and then you may have a disc car master cylinder? not sure?

A full bleed would be a benefit, start from the passenger side rear, then drivers side rear, then passenger side front and finnaly the drivers side front! I use a 16 oz water bottle (empty) with a 1/4 inch hole drilled into the lid, then a couple of feet of 1/4 inch clear air hose (like on a fish tank) so you can see bubbles in the line! best way I have found, Don't let the master cylinder go dry, keep an eye on it and fill as required! Quick and easy with two people!

Another thought! remove the vacuume hose from the brake booster and plug the hole in the manifold and see if it changes pedal feel!

John B.
 
I will mention that every brake part on the car is new,this is how I bought it.The PO had everything done by a licenced mechanic(his neighbor).I guess I,ll have to pull the wheels and check everything to make sure alls good and might aswell bleed the system just for piece of mind.This way atleast I,ll know it was done and no air in the line.It could be just me being used to new vehicles,cause I drive new vehicles at work every day.We,ll see?Thanks for suggestions.
 
You must log in or register to reply here.
-

Back
Top