+- Carolina Broncos (https://cb4x4.com)
+-- Forum: 66-96 Ford Broncos (https://cb4x4.com/forum-7.html)
+--- Forum: Bronco Tech (https://cb4x4.com/forum-40.html)
+--- Thread: Brakes bled and pedal goes to the floor but I do stop... sort of. (/thread-1809.html)
Brakes bled and pedal goes to the floor but I do stop... sort of. - chuzie - 10-20-2009
I adjusted the piston pushrod out a few turns just to see what it would do. The braking action is not better however the point at which the braking action occurs has become sooner in the pedal travel rather than later so this tells me I am getting full use of the stroke now as well as before since there is not a performance change.
Checked out the calipers today to see how the lack of a residual pressure valve was affecting the system. I agree it would not affect performance unless the pads we so worn that it was taking a significant amount of fluid just to get them in contact with the rotor. The new pads are pretty tight. I can barely get a piece of paper between the pad and rotor when the brakes are released. Now this is not to say that the recent pushrod adjustment has had nothing to do with that and I am sure, without the valve, I will have to occasionally re-adjust the pushrod to maintain that gap but that is not an issue right now.
Re-adjusted the rear brakes further to make sure I am not wasting too much pedal on the rears not effectively stopping.
Pulled the hose and valve off the booster and got the WOOSH so we know that is good too.
Talked to a good mechanic friend the other day about bore and stroke and with my 1-1/8" bore and identical stroke I should have great braking regardless of my stock calipers.
Still at a loss
URE is less than a month away and I still am without brakes.
Brakes bled and pedal goes to the floor but I do stop... sort of. - broncomatt - 10-20-2009
Give me a holler to night mike and we can work on it again. Well get if figured out one way or another.
Broncomatt
Brakes bled and pedal goes to the floor but I do stop... sort of. - chuzie - 10-20-2009
wilco
Brakes bled and pedal goes to the floor but I do stop... sort of. - blazinchuck - 10-21-2009
did yall talk...whats the next plan? i swear, im at a dang lose! I mean dang, I ran chevy calipers, ford drums, with a manual f250 MC...and those were better than what you're having right now Mike-just dont get it!
Brakes bled and pedal goes to the floor but I do stop... sort of. - chuzie - 10-21-2009
Matt is a very knowledgeable dude. We talked for a while and he gave me some suggestions to try and narrow down the problem.
He had me adjust the rears almost all the way out and extend the pushrod a little further. Then I jacked the truck up on stands to see if the brakes would hold the wheels under a load. They don't.
Initially when I place it into drive with the brakes fully applied I get a hair of movement from the rear. Then when i do some power braking the rears spin. I also tried it in 4-low and all four tires would spin, with resistance of course.
I think he is concerned about the master cylinder at this point. Waiting to hear back from him today.
Brakes bled and pedal goes to the floor but I do stop... sort of. - broncomatt - 10-21-2009
You have given me enough information that I would condem the master. The fact that the wheels turn in 4low doesnt mean much (low gears overpower mechanical force). But when you put it in hi range and burp the throttle the rear wheels moved. That tells me that the master cyl you have is not the correct size to match the rear wheel cyls. Plus since the master cyl is at the end of the stroke it is not moving enough fluid to completly hold the fronts either. It may have the correct bore, but it may have too short of a stroke.
I hate to see you put more money into it (especialy with rear drums) but I think the best thing to do would be buy the master cyl from duffs.
The only other thing too do would be find out what the bore and stroke of the master cyl duffs offers is and then find someone at a parts store who can look them up by the bore, stroke and mounting flange.
I will bring my tools to URE too show you how to adjust the brakes correctly and bleed all four wheels. Let me know what you decide to do.
Broncomatt
Brakes bled and pedal goes to the floor but I do stop... sort of. - chuzie - 10-21-2009
Since I have the old Duff's MC and suspect they use the 1969 Cadillac El Dorado for their setups I can easily match them. I know they are both 1-1/8" bore but need to match the stroke. Can I match the stroke without removing the piston using a depth gauge? until the piston hits the stop?
Brakes bled and pedal goes to the floor but I do stop... sort of. - broncomatt - 10-21-2009
Not sure if there is an acuret way to do so with out taking it apart. You may be able to put it in a vise and compress it all the way in and measure the depth(stroke).
You should be able to call a parts store or look on line ( I use advance auto parts on line site ) too look up the caddy to see what parts it came with (did it have drum rears, caliper fronts, a prop vavle, vacume booster). They may even have specs on the factory drum size.
You should also try and positivly identify what size drums (that will tell you what size wheel cyl you have). That will make fitting all the parts together more acuret.
Broncomatt
Brakes bled and pedal goes to the floor but I do stop... sort of. - bound4dixie - 10-22-2009
ok, I'm thinking out loud here..so Matt or anyone else please let me know if my logic is wrong...
The master cylinder you are using is a tandem cylinder, correct?
Tandem styles are designed with two pistons in a common bore. They are suppose to be more safe than single piston because each piston feeds an axle, so if there happens to be a leak in the line to the front, the rear will still work properly because it is its own contained system.
Is it possible to plumb the system so that all of the fluid goes to the front axle only? This should eliminate part of the fluid demand on the master cylinder and therefore the pedal should not move as far as before.
If it does move just as far as before....the master cylinder is shot
If it moves less, but you still have to stand on the pedal to get the wheels hold...you need bigger power boost or a smaller bore master cylinder to increase the mechanical advantage.
The other option is to find ya a brake or hydraulic pressure gauge and plumb it inline. A leaky master cylinder shouldn't be able to generate or hold pressure for long.
Like I said, I'm just thinking out loud. Comments?
Brakes bled and pedal goes to the floor but I do stop... sort of. - bucketobolts - 10-22-2009
Does the pedal get any better if it is pumped?