i have a 58 F100, on the way back from Primer Nats. the stock single jar started leaking. so i decided to upgrade to a dual master cyl. i bought one for a 69 Mustang w/ manual brakes and a for a big block. i put it on and for some reason it just slows me down if had to do panic stop i would keep going. if i pump them twice it feels better. i've bleed the brakes with a mighty-vac that work some what then i did it old school with a jar and fluid. it's gotten a little better but it just slows me down. i checked for leaks and everything is tight. what else can it be? maybe they gave a master cyl for pwr brakes?
it mounts on the firewall..... yes the push rod is the same length. mine looks just like this only without the Wilwood. the front res. for the master is for the front brakes and the back for the back, right?
uuuhhh as a general rule, the BIG resivoir is for the front and the little ony is for the rear. yes, they can end up in either spot. (front or back)
i may be crazy , but i don't see any line coming out of the proportioning valve to go to the rear.. also, what do you have for brakes? drum/drum or disc/drum? for drum/drum you may not need the prop valve
that's a sample picture. my set up looks just like that. lines are the same way and everything. the only thing is that mine doesn't have the proportioning valve. my truck is set up drum/drum. all i wanted was a dual master cyl. my leaking master stopped better than this one.
Dumb question time.....does your replacement M/C have the same piston diameter as your origional???? If it's LARGER you will have INCREASED your pedal effort while reducing your pedal travel. However you also describe that pumping it up improves things.....which means you aren't blead properly yet. And I agree with the LUX BLUE - the FRONT reservoir doesn't necessarily always go the the front brakes - I have several factory braek setups that the front actually goes to the rear. A clue can sometimes (not always) be in the fitting size - the larger diameter fitting/line is usually for the front disc brakes. Also the dics brake side will always be the larger side. Drum/drum masters are usually the same size on both sides, but I still believe that the primary reservoir is the rear reservoir (closest to the pedal) and therefore gets plumbed to the FRONT (primary) brakes.
Your set-up can't be just like the one shown--that guy has the rear reservoir controlling all brakes, the front going to the brake light switch then on to an adjustable prop valve, then nothing. What everyone said about the larger chamber being for the front brakes is correct. I've heard a bunch of guys with this SAME problem in the last couple months (a surprising number, actually!). Did you bench-bleed the master cylinder? Every one of the guys I know did not bench bleed. And bench bleeding was the cure. I don't know why air stays trapped in the master when it's mounted, but it does. Give that a try. -Brad
If you have a 69 Mustang m/c for non power 4 wheel drum brakes, then both resevores will be the same size. The rear chamber still goes to the front brakes and the front chamber to the rear brakes though.
drum brake masters have the same size bowls, it really doesn't matter which goes where on a 4 wheel drum. might re check the dia of the bore, if it's larger then you'll have to push a little harder. i would also get some one to help bleed system again (the old fashion way). bleed master, then bleed pass rear, driver rear, pass front, driver front......pump alot and keep filling the fluid (at least you'll have a clean system for a little while). i put a dual master on my 64 panel (1/8" bigger bore), ran a new line.......but it took a little bit of pumping to get all the air outta the pass front, now it works like a charm. i just looked in my parts book, the books say a 58 f100/150 is a 1 1/16" bore and a 69 mustang is a 1" bore.....i would try to bleed again.
The difference between the 1-1/8 and a 1" master bore isnt shit - it should work fine. What is going on there is explained by your having to pump it, to achieve any braking power. You do not have enough[ or possibly too much] free play between the push rod to the piston in your master.... Look at it this way-if the piston is not returning all the way[ too tight] it will not reach the point in the reservoir where the small hole is bored DOWNWARD to allow fluid to flow INTO the bore and then be displaced by the piston..therefore it isnt getting a full stroke really and the second pump bolsters this lack of action. If it was a pushrod that is "too loose"- situation you would be in effect moving the piston LESS than a normal amount for its pedal stroke,resulting in a weak brake feel. also tightening all four of the shoes all up to [where they barely drag when turned by hand]....is pretty important too!
okay i know for sure it's for drum brakes. both res. are the same size. the front of the master is going to the front and the rear to the rear. i did bench bleed the brakes but i just remember that when i was doing it i was called away to do something. so i might still need to bench bleed it some more. i will do that and rebleed the brakes with the mighty-vac and old school. the pushrod that came witht he master was exactly the same length of the old one. thanks for all the help guys. i'll give you guys an update soon.
The pushrod is the same -that is a given....BUT the piston definitely is different -yes? that could be the problem....unbolt the master a few turns on its two nuts and see if there is free play- I bet that is a possibility.........good luck.
On one of my cars the difference in leg force between a 1" and a 1-1/8" master cylinder diameter is 200 and 256 pounds - which is basically a 28 percent INCREASE in pedal effort. I guess to some that ain't shit - but to others it is.
it sounds like air to me, but to be safe make sure there is a little free play in the pedal. you'll feel a little movement before the rod hits the piston. you had to run a new line for the front or rear and i bet there is still some air. i've had good and bad with the mighty vac (or vacuula) on customers cars so i like to do it the old way. what might happen is the side you ran the new line to will bleed off some fluid for a couple of pumps and then no more fluid..........that's where the fun starts. use a clear hose or a bucket so you can see air coming out, just pump the living shit out of the system until there is no more air. this sounds like overkill but sometimes it takes a while for air to get to the end of the line.
just so i know.... i have my daugther pump the brakes for me. i have her pump 4 times then hold the pedal. i bleed it watch the bubbles then close it. repeat like 3 times or as many times as it take. from the pass rear and work my way to the driver front..... now i've heard someone say you should go from the driver wheel first. what do you guys think? "I prefer to bleed a new setup backwards from the recommended method, starting with the wheel closest to the MC and working to the one furthest away. That way you are evacuating the majority of the air thru the shortest line, requiring the least amount of refills of the MC. Never really made sense to me to push all the air thru the longest line! Be sure you don't empty the MC between bleeds and reintroduce air. Note: it may take several bleeds to remove all the air from the longest line especially if there is no residual valve the air will want to migrate back towards the MC."
Only if you are weak in the knees...... that suprised me HemRamb'....I meant in the end result of the piston actuating the brake cylinders it was insignificant.
the rear chamber (closest to firewall) goes to the front brakes. you need freeplay in the pedal. adjust accordingly. does the pedal go to the floor? how far does the pedal travel before it activates the brakes? if you pump it, does it stop better? bleed furthest to closest. (rr, lr, rf, lf) open the bleeder and have someone push the pedal to the floor. hold the pedal on the floor. close the bleeder. repeat a couple times on each wheel cylinder.
Choprods - I guess I misunderstood your point. I agree - the systems gotta work FIRST And just for the record - I still get weak in the knees - every time I see a ....... with a nice big set of headlights and again when she ...... over and I get a look at....... nice narrowed rear end....hummmina hummina hummina.
you are correct, just keep checking the master after a few bleeds so you don't have to start all over again.
All 69 Mustangs had a 1" bore MC except the Boss 429 at 9/16" Your 58 if is a 1/2 ton it would have had 1 1/16" MC bore. Very close. Keep bleeding and also check your pushrod and freeplay etc.
i was always undeer the impression that a new MC needs to be bench bled before installing... then bled again normally. is this true? bench bleed the MC regardless... air does get trapped in there.
if the system is air free then you can get away with bench bleeding only (and not the whole system). also you dont have to bench bleed the master, but it pushes the air into the system and makes it horrible to get all the air out. i've done it on the street (in the middle of nowhere), put the master on the firewall, hold your fingers over the holes, have another person slowly pump the pedal to bleed the master.......it's not pretty but it worked.
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