what a drag!!! (1 Viewer)

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Nov 11, 2008
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Clarkdale/flagstaff
hey guys im having problems with my brakes on my 71, 40. lil while back did a disc brake conversion got a new master cyl from checker(76) .the problem is they dont turn off ? once you hit them once or twice the pressure builds an it is like riding your brake all the time :mad: im at my wits end why would it keep pressure in the sys, things i have tried fliped the check valve shortend the linkage it is not draging:hmm: if you break the line loose:wrench: at master all the pressure goes away till a few pumps:mad:
 
You've taken the residual pressure valve out of the circuit at the master that feeds the disks, right?
 
the litle check valve on the master??? before the hyd line???
 
Yes, at the master before the hard line. That is a residual valve that keeps pressure in the circuit in order to keep shoes close to the drum. In a disk brake application, that residual pressure is too much, leading to dragging brakes.
 
Another thing is, the push rod from the peddle to booster and from booster to master must have play. If not the master can be held slightly depressed, if so it wont bleed the fluid back into the reservoir, causing them to bind/build more pressure each time the peddle is pushed.
 
hmmmm:hmm: ill try that , what was the first year of disc brake on a cruiser ? thought it was 76 told them to get me a disc brake master , was i wrong ? the first or second year disc brake master i thought would work for my app , ill take that check valve out tommorow.. thx:D
 
Another thing is, the push rod from the peddle to booster and from booster to master must have play. If not the master can be held slightly depressed, if so it wont bleed the fluid back into the reservoir, causing them to bind/build more pressure each time the peddle is pushed.
cut that lil sucker down when i first started this :mad: their is play before engagement;)
 
hmmmm:hmm: ill try that , what was the first year of disc brake on a cruiser ? thought it was 76 told them to get me a disc brake master , was i wrong ? the first or second year disc brake master i thought would work for my app , ill take that check valve out tommorow.. thx:D

If you've got a master for a disk/drum application already - any chance the lines are switched?
 
well i was supposta have a master for a disc brake but now i wonder ???:doh:
 
well i was supposta have a master for a disc brake but now i wonder ???:doh:
Howdy! 76 was the first year for disc brakes on the 40 and 55 series, but it was only on the front axle. The rears were still drum, so still had the residual pressure valve. Didn't you mention in a different thread that the rears were dragging? John
 
well i just put the back brakes on yes i tried to get them close! they drug a little but not bad . this is stopping before you can get it in the next gear:mad:
 
thought it was 76 told them to get me a disc brake master , was i wrong ? the first or second year disc brake master i thought would work for my app , ill take that check valve out tommorow.. thx:D

who is "they" :confused: you don't expect Napa and the like to know, do you :rolleyes:

some of the master cylinders are no longer available OEM, and the aftermarket may not specify year correctly

which axle did you convert ? front ? you still have drums on the rear ?
 
worse yet i went to checker:eek: well they were close to the house, converted front with 40 parts from later year
 
worse yet i went to checker:eek: well they were close to the house, converted front with 40 parts from later year

I assume it's the same Checker's in Fountain Hills we go to - as there is only one :doh: :D

yeah, those dudes need serious education as far as cruisers are concerned :rolleyes: they can order stuff, but you have to know what you need :doh:

so I take it the front is dragging ?
 
well took that check valve out of front now the back locks i shortend the lil push rod we went out on a lil run and drivers rear locked by the time we got ther it was smokin:mad: so i bled pressure off mast cyl an rode around the rest of day no problems i think im taking check valve out of the back to!
 
why would the driver's side rear brake lock and not the passenger side at the same time :confused:

air in some line and not the other side ?
 
the right ones probibly adjusted right:D
 
Bro, Tools R Us had it right, but may not have described it well. Skip the pedal and booster. If the piston in the master cylinder does not return all the way to the at rest position, it is like pumping up the hydraulic system. It will keep putting pressure on until the brakes lock.
The master cylinder piston must return all the way to bleed pressure off of the system. Then the brakes can release.
First, make sure that your Master cylinder is relaxing enough to let the pressure off of the system. Then look at the pedal and booster push rods. Insure that they each allow enough play to let the master cylinder return to the relaxed position.
If for any reason the piston in the master stays pressed foreward even a bit, it will not bleed off brake pressure, and the brakes will lock.
 

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