i just bougt a master cylinder for my 74 f100 4x4 and it needs to be bench bled can any body tell the proper way to do so
thanx paul

 

fill the res with clean dot 3.

insert adapters, and hoses into all the ports. feed the other end of the hoses into the res. make sure to keep them under fluid at all times.

clamp the MC in a vice. using a screwdriver..depress the MC, make sure and keep the res full. do this until theres no more air...

 

it did not come with adaptors so can i just find the right size hose and cram it into the hole and cap one at a time or do bolth have to be done at the same time

 

we used to clamp mc in a vise, fill the resevoir with fluid, put a finger over each hole, slowly push piston in allowing fingers to get pushed off the holes. as soon as piston bottomed, fingers were sealing the holes up as the piston was allowed to return. that puts fresh fluid in the bore. a couple of pumps should displace all the air.

with the piston not depressed, reinstall the plugs to minimize fluid loss. take mc to vehicle and install. remove plugs, place fingers over holes, have a second person in the vehicle depress the pedal slowly (allow fluid to exit mc) and then hold it down on the floor. with pedal fully depressed, remove fingers and install the two brake lines. when both are tight, helper can release the pedal - that will pull any/most air in the lines back into the resevoir. then bleed mc once or twice by slowly (you don't want to foam the fluid IF there is still air in the lines) pumping pedal two or three times, holding down, cracking open the lines and releasing fluid/air. tighten fitting, let pedal return to top, repeat once or twice more.

i have used this method since 1974 and only once or twice have i ever had to bleed the system at the wheels when just replacing an mc.

holding down the pedal until bleeding is over allows the mc to pull air in the lines close to the mc back into the resevoir where it will then come out of the fluid.

have water available as brake fluid dissolves paint and be careful not to squirt fluid in your face and eyes - open fittings slowly.

neil

 

neil i have done as you have told me now i have a problem with the break peadel not staying tight lets see if i can explain when i hit the breaks the peadel goes close to the floor but i have good breaks if i pump them once or twice they are where they should be but after releseing them they go back close to floor does this mean i need to bleed them again or is this another problem
thank you paul
ps also i noticed when i bled at the wheels the backc wheels empty the front resavor is this correct or is the lines crossed

 

sounds like there is air in the system. sorry. you can try to bleed at the mc a couple of times, but most likely you will have to bleed at all the corners.

i do not know from experience, but if the mc has two resevoirs and they are diff sizes, the larger resevoir will be for the front disc brakes. often the front brakes use a larger piston so in a tandem master the front resevoir IS for the rear brakes and the back res will do the fronts. the piston is usually a single piece and so the smaller bore must go in the deepest part of the bore then the bigger bore follows....

neil

 

you can try to bleed at the mc again once or twice. pump a couple of times slowly until pedal is firm then crack both fittings open. repeat. do this with the ebrake on - (if the brakes are out of adj, they will pump up and fool you into thinking there is air in the system...)

if you have to bleed at the wheels, start with the wheel furthest from the mc. don't let the mc run dry!! so usu RR then LR then RF then LF

yes front resevoir very likely for rear brakes. if the resevoirs are two diff sizes, the larger res will be for the front. it is just the way a tandem master is made - smaller bore is for rear brakes and has the be bored first, then larger bore for front is bored. piston is usually one piece so the small bore has to be first for the piston the fit.

neil

sorry for the repost, hit the wrong button after editing and thought it toss my first reply...

 

neil i blead those breaks again twice in faact and still get soft so i tried to adj the breaks the back moved out but could not get the front to move mabey the adj could be stuck.in the 74 they should be self adjusting am i correct . should i try to buy one of those self bleeder vacume things or should i just try to bleed them the same way.
thanx again paul

 

you need to get them adjusted first, then bleed. pump'em up, the bleed. if that does not seem to work, you can attach a hose to the bleeder, pour some clean brake fluid in a clear bottle, submerge the end of the hose in the fluid, crack the bleeder open, then slowly pump the pedal up and down. when the bubbles stop coming out, hold the pedal down, tighten the bleeder up, then move to the next wheel. start w/ the furthest wheel and work to the closest. don't let the master run dry.

the two methods i have discussed have worked for me for the past 35 years. i still don't use/own a pressure/vacuum bleeder. never needed one.

you would have to look at a manual to see the charact3eristics of the braking system. i never really worked on american rides until i bought the van. so i am a poor reference unless discussing 1995 E350's w/ a 460 EFI motor and an E4OD...

sorry

neil

 

thanx neil you are a lot of help to me

 

I have a 2000 f150 with the 5.4, had a spongy pedal feel so bled the brakes at all four corners. I started at the wheel furthest from the master cylinder first working from furthest to closest. In addition I had an airtight seal on the bleader valve with the hose so was able to just leave it open until the clean fluid came out. If you do not have an air tight seal when the brake pedal is let up from the floor make sure you close the valve first. To do this you must have an air tight seal and the other end of the hose must remain submerged in the brake fluid. Also since the old fluid looked pretty dark I bled the brakes until the fluid came out clean. Anyhow works great now, did take about $15 of fluid!

 

yeah, if you look at most factory recommendations, you are to flush the brake system every couple of years. brake fluid is hydroscopic - that is it absorbs water. despite the sealed up master cylinder with exclusion boots etc, moisture still makes it into the fluid and slowly breaks it down raising the boiling point and giving you a crappy pedal and rusted lines/calipers. plus heat also breaks down the fluid. so when you see dark fluid, that is contaminated fluid. i flush mine every two years.

juchertf100, i appreciate your kind comment. i also hope you got your critter back on the road!

svt4cobra6, yes i agree an airtight seal is best, but when there is a lot of air like when the system is being filled for the first time, sometimes the pump it up method won't work so i just open the bleeders a turn, attach hose, put hose in bottle of clean fluid and slowly pump to purge MOST air. what i failed to advise juchertf100 was that he should return to each corner and use my first method to ensure a fully bled system.

neil

 

wow did not realize the brake fluid absorbs water, perhaps this was why the pedal was a bit spongy.