Ok, I've run through pretty much everything I can think of and my brakes are worse than ever. I decided to try and fix my spongy pedal problem and cannot figure it out. I've run through some things and cleaned up the front, but still nothing. Here's what I'm running: 1949 dodge wayfarer -Fatman Mustang II stub -ECI 11" front brake kit (uses '70-'77 camaro calipers) -'58 Ford 9" rear with big brakes (stock, rebuilt cylinders) -Mp brakes universal hanging pedal: Originally, the booster was under the floor, but we moved it to the firewall for exhaust and ground clearance. As such, we just have the 7" street rod booster from MP brakes. The master cylinder was changed when we were originally trying to get it to work for a replacement one from the parts store. I've since found that the original m/c had a 1" bore and the replacement has a 1.125" bore. However, the one that's on there now has the same bore as the one for the calipers. The system is plumbed like this: The caliper bleeders are pointing straight up and the calipers move in and out on their pins as they should (thanks El Polacko!). I ran a check on the master cylinder per MP brakes' instructions, here: http://www.mpbrakes.com/how.htm It checks out fine, nice hard pedal with the lines plugged. If I clamp the front hoses, I get a hard pedal, but if I release either front clamp, it goes to the floor. If I clamp the rear hose, it still goes to the floor. This tells us the problem is in the front right? The brakes have been bled over and over and still no air coming out of them. I bled them in the correct order too, right rear, left rear, right front, left front. I cannot find any leaks in the lines. The car is running DOT 4 fluid. I've tried everything I can think of as well as everything that was suggested. Any insight? The only thing that I can think of is that I'm not getting enough pressure. When I bleed the brakes it doesn't squirt out like every other car I've ever bled. Could the bore of the M/C be the problem? I found this chart on Mp brakes' site that tells the difference between bore and pressure and I can see I'm not getting the same pressure (note, the pedal ratio has not been modified): THE EFFECT OF PEDAL RATIO AND BORE SIZE ON HYDRAULIC PRESSURE OUTPUT Pedal Ratio Bore Size lbs input PSI out 6:1 1 1/8 75 453 6:1 1 75 573 6:1 7/8 75 748 5:1 1 1/8 75 377 5:1 1 75 477 5:1 7/8 75 623 4:1 1 1/8 75 302 4:1 1 75 382 4:1 7/8 75 499
WF - I got rid of my small power brake booster and went to a manual master cyl and my brakes improved considrably. It gives less pedal actuation and squishyness. I really don't thinkn the smaller boosters work as well as the regular ones.
Even so, my pedal should be firm without the car running, right? I may have to go manual, but since I already have the booster mounted it should work even if it doesn't provide enough ***ist. Thanks for the suggestion, though.
Way.... I hate to sound like a broken record--but--- I still point the finger at the master .....Did ya ever buy anthing new that was BAD ???I sure have.... the ULTIMATE way to troubleshoot the system is with a pressure gauge ....beg,borrow,steal or buy one .....it will tell you where the problem is .....personally, I would take the master back and try to get another ....and make sure the chamber you have piped to the front ACTUALLY IS for the front ( take a look at a stock car of the same vintage ......a slight chance--but ---if the combination valve is the bad component(or piped incorrectly) you'll be shootin' in the dark tryin' to solve the problem .....easy enough to take IT ( comb. valve) outta' the system and see how the pedal feel is..( I know it's a pain in the *** but you've tried everything else)then all that is left is the MASTER .....my .02..... Jersey skip
Ok, I'm going to try and find a m/c this afternoon. The question is, do I need one with a 1" bore or the bore that matches the front calipers? Does anyone know which chamber of a camaro caliper goes to the rear brakes? I have it plumbed like above, but that may not be right.
Wayfarer- The proper MC for power brakes should be 1 1/8th. That is what was used with the Camaro calipers you are using. The 1 inch was used with manual brakes (no booster). I use a 1 1/8th on my roadster with '68 vette calipers all around. It raises the pedal pressure your foot has to provide but it stops just fine.
Well, my master cylinder's right, then. If I plug the outlets, I get a really hard pedal, which, according to MP brakes' troubleshooting site, means that the master's good. Could my combination valve be bad? I know I'm not getting the pressure that I should.
Calipers are retracting too much. It takes all the pedal travel you have to re-fill them untill the pads contact the rotor. Even though you mentioned you removed the metric calipers and replaced them with the correct ones, I belive the O-rings are of the later style. Check the clearance between the pad and rotor. I would almost bet you can see daylight there and you shouldn't. If by some chance both pads are touching (or nearly) the rotor and you still have this problem there has got to be some air in the caliper that you cannot get out. Those are your only choices. If for some freak chance you have a bad brake hose that is expanding under pressure but that should only happen with high pedal effort. Get a rebuild kit for the early Camaro these are supposed to be off of and rebuild them yourself.
You might try to isolate your problem. Plug the line going to the front or back,rebleed, and see how it is. You can narrow down posible probs. I feel that you may have a high point in your lines somwhere that you can not blead the air out of. Especially bad with 1/4" lines. Good luck.
[ QUOTE ] Calipers are retracting too much. It takes all the pedal travel you have to re-fill them untill the pads contact the rotor. Even though you mentioned you removed the metric calipers and replaced them with the correct ones, I belive the O-rings are of the later style. Check the clearance between the pad and rotor. I would almost bet you can see daylight there and you shouldn't. If by some chance both pads are touching (or nearly) the rotor and you still have this problem there has got to be some air in the caliper that you cannot get out. Those are your only choices. If for some freak chance you have a bad brake hose that is expanding under pressure but that should only happen with high pedal effort. Get a rebuild kit for the early Camaro these are supposed to be off of and rebuild them yourself. [/ QUOTE ] That is the same basic thing that enjenjo told him on sunday, here
I don't have the metric calipers. I thought I did, but once I pulled the wheel, the ones on the car are much larger. I looked up my paperwork from fatman and they are '70-'77 camaro calipers. Not anywhere near the same as the metric ones and the pads are touching the rotors. It's not the calipers retracting. I resent FatCat acting like I already knew what was wrong and am wasting everyone's time. On Sunday, I ***umed I had the metric calipers and after reading a post thought that may have been why I could never get the brakes to work right. After pulling off the wheel, they are not metric calipers! If they were, I would have changed them and been on with it. All I asked for was a little help, but please read the setup I have before making stupid comments. I tried to include everything in the system so there wouldn't be any questions. I guess it's the master cylinder and am replacing it tomorrow. Thanks to all those who helped, especially El Polacko, for giving me suggestions. I come here for help and to help others, not to make stupid comments. Thanks again, guys who helped.
I nor enjenjo mentioned anything about metric calipers. He said it was the seals on the new calipers that were causing the piston to retract. From watching this thread I was pointing out that you never mentioned whether you checked it out yet. Quoting enjenjo [ QUOTE ] It could be air in the calipers if the bleeders are not at the top. If the bleeders are at the top of the caliper, you need a residual check valve to hold the pads closer to the rotor. What is happening, the caliper seals are retracting the piston so much the pads don't contact the rotor until the second pedal application. The older caliper seals didn't do this, but the newer seals do. If you drive it a few thousand miles, it will probably correct itself, but a residual valve will fix it now. If you already have a Wilwood residual valve, replace it with one that works. MPB sells Wilwood, along with Speedway and most of the others. I use Stainless Steel Brakes, or Sierra Residual valves. [/ QUOTE ] I don't see the word metric anywhere in there. If its there point it out. You can resent it all you want, but did you check it? If not get off my back because it was suggested already and you misunderstood it. And for your info I have seen this happen with 70-77 camaro, 82 Ford LTD, and Mustang II calipers. This is not something that pertains only to Metric GM calipers What he meant by newer doing it and older not was the material used to make the seals not the application of the part.
I'm hangin' on this thread like stink on a monkey, cause I'm still fighting this problem like you are...and I'm sure there are others. I've got such a *******ized system, I don't know where to start; Camaro brakes (disk,drum) Maverick pedal, Torino mc, and Mustang proportioning valve. Yikes! The **** I do to save a buck. My system is manual...takes one pump to get decent pedal. No air in lines (my poor wife, the pedal pumper). One thing you said about the pressure not being as much other brakes got me wondering about your pedal. Could it be hitting the floor before the rod bottoms out in the mc? This may be my own problem, since nothing is stock. Maybe a longer rod, at least during bleeding, to get that last bit of air out. Good luck and let us poor souls know what works for you.
Fat Cat, sorry for getting on your back, but enjenjo said that I needed a residual pressure valve to correct the problem, not that it had the wrong kind of seals. I already have a combination valve in the system that includes a residual pressure valve. I replaced the master cylinder this morning. As soon as I can get someone to help me bleed the system, I'll let you know what happens. I tried moving the pedal out and still no dice. If the m/c doesn't correct it, I'll rebuild the calipers.
way... if ya can get a PRESSURE BLEEDER it would be a big help in making sure NO air is in the lines .....NOT a vacuum bleeder ----PRESSURE bleeder.....(and it HAS to be the Master or the calipers--or both !!).( ***uming the combination valve is good...). Let us know what the end result is..... jersey skip
If MP Brakes told you there is a residual pressure valve in that combo valve you got from them, they were pounding sand in your ***. I have had their combo valves apart, and there is nothing resembling a residual pressure valve.
i just put 11inch disk with 1 piston cals new danchuks ss prebent lines new 7 inch booster new combo valve ..no brakes..power bleed..pump bleed graviti bleed no braks..co to the floor..this stuff came as a kit..i can clamp both lines and i have a hard pedal,,great rears..but if i want drums i would have kept the tridlevac,,on my 56belair.but stoplng a 400 hp 327 was not to good with dums,,now i at a dead end..wroung master cy maybe..neever in my 52 years have i had this problem bleeding brakes..what am i overlooking
This may sound simple BUT.... If you have your plumbing setup like the picture shows in your first post, the primary piston is working on the rear brakes ! Try swapping the pipes over in the M/Cyl outlet ports. You are trying to push past the rear system to fill the front, not as it should be.
More info .... ALL THIS **** ABOUT OLD STYLE AND NEW STYLE PISTON SEALS !!! AND PISTON PULL BACK. In actual fact the pistons retracting excessively in the bore is caused and is directly proportional to the clearance between the seal groove and the seal ( width of machined groove the seal sits in). If the groove is machined too wide it can allow the seal to roll on its seat under pressure and pulls the piston back after pressure is released. Im talking of errors as small as 0.10mm here making a big difference to the pedal feel. And another thing, what is hotroddings fascination with residual valves???? never seen one in my life. And a backyard tip for pressure bleeding.... First ensuring the cylinder has been bench bled before fitting: Get hold of a spare M/Cyl cover cap, drill a 1/8" hole in it , fill M/C and put cap on. using very low pressure compressed air or even a bicycle pump, apply pressure to cap and it pumps the fluid thru to the opened bleeder of your choice. N.B... dont let the m/cyl go empty during bleeding. if the bleeder ****** has a small tube fitted off it running into a jar of fluid you can do a one man pressure bleed without fear of air entry.
The way the Bendix rep explained it at one of their seminars is... the walls of the groove in the new style caliper are not parallel. The outside wall of the groove leans slightly toward the pads. As the piston moves out, the seal is allowed to lean or roll until it contacts the leaning wall of the groove. When the pedal is released the seal "memory" returns to it's normal straight up position pulling the piston back with it. This was done for fuel economy. Reducing any pad drag. They were doing everything the could to meet the govt. mandated fuel economy standards. These type calipers require a "quick take up" master cylinder. The QTUM/cyls have a step bore (larger to the calipers) to move a larger volume of fluid quickly. When they first came out we were warned not to use the cheaper old style m/cyl. as a replacement. I'm not saying that is your problem. just trying to explain what I was tought. When we have a problem child, we use vise grips or brake hose clamps to lightly pinch off the 3 or 4 rubber brake hoses. If the m/cyl is ok you'll get a hard pedal. Release each clamp one at a time. When you find the offending wheel/s the pedal will fall. At least you know where the problem is. PS I agree with your supplier if you block off the m/cyl ports and you have a hard pedal, I'd say it was fine too.
well i back were i was stuck blocked off both front lines to cals ,,great pedal..only thing i can fig is the mastercyl is not made for or matched to the cals
[well i back were i was stuck blocked off both front lines to cals ,,great pedal..only thing i can fig is the mastercyl is not made for or matched to the cals] Why did you resurrect a post that's almost a year old, and has nothing to do with your problem (other than it involved brakes) to make your debut on the HAMB? Just curious. Mutt
And another thing, what is hotroddings fascination with residual valves???? never seen one in my life. Ha I like that... I have done a bunch of rods and no stupid valves and now im using them on my 32 ? but i did a 30 model a this summer disk front drum rear no valves stops great and the pedal feels good too. Just to rile up FatCat a little more Ive used the wilwood residual valves on 3 cars now 2 were my own and no problems so what did you do to piss them off and get bad valves Dave
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