I explained on another thread the problem I'm having getting a good hard pedal on my 64 Fairlane. Here is what I've done so far. All hoses are new - New wheel cylinders - New Master cylinder x 2 - New calipers and pads - Like new shoes - Bought the $30.00 power bleeder and ran a couple of qts of fluid through the system - Bench bleed both masters - Cracked lines at master cylinder to bleed - Bypassed line lock - Installed residual valves front and rear - tightened the rear shoes all the way - Removed the calipers and let them hang down and bled them. This is a Scarebird system that uses G.M. calipers and hoses with 68 Mustang rotors [all new] . This is not Scarebirds fault as everything bolted right up. Next on my list is a proportioning valve, which like the residual valves everyone says will not effect the firmness of the pedal. I have considered checking into some pads that have the stainless shims included thinking that might have the same effect as tightening the back shoes. The rotors due turn pretty free right now. I'm out of ideas other than that. Somebody pull this car off me please! It's kicking my a.. and my wallet! Thanks for any ideas. tommyd.
Dont know if this has anything to do with it but when I mounted my master to my booster I didnt put in the little spacer that essentially extends the stroke of the pushrod in the booster so that it fully presses on the master piston. Basically my pedal would go all the way to the floor and barely get firm. Someone here mention that and there it was in the bag of leftover parts. Apparently some master cylinders have a deeper bore depth than others and it wasnt long enough to push the piston all the way.
Thanks for the suggestion. I don't have power brakes but my m/c also came with that piece. I ended up cutting most of it off and used it to extend my pedal travel. I didn't know what it was for. Appreciate the response. It's keeping me from setting my car on fire right now.
At this point I believe I'd remove the rear brake lines from the junction and plug off the hole...try the pedal to see if it'd better with only front brakes operating. If so the problem is with the rear brakes. If it doesn't help, try the opposite with fluid only going to the rear brakes...if it's still no better the problem would be your master cylinder. If it helps, the problem is in the front brakes... Narrows the problem down a bit...
correct rod from interior pedal arm to M/C booster? what type of intake manifold- where do you have hose to booster hooked up at? pics?
What type of MC are you using and what is the bore size? I had the same problem when I converted my '64 Galaxie to 4 wheel discs. The MC that came with the power brake conversion kit had a 1" bore, and it wasn't moving enough fluid to activate the calipers, which was part of a separate kit. Turns out that it took more fluid to activate the calipers that it did the wheel cylinders on the original drum brakes. Replaced the 1" MC with a 1 1/8" MC, problem solved. Chris
Just manual drum disc combo. Dang it Rocky, you or someone else suggested blocking of the m/c on the last thread and I forgot. Thanks for the reminder. Do that tomorrow. I'm pulling the rear drums back off also to double check everything. Thanks shadams and jalopy joker also.
Its a GM Corvette style from Allstar Performance with a 1" bore. The first m/c was a Ford Granada style with an unknown bore. I had wondered about that but figured a 1" bore was big enough since I only had front Discs. Thanks for the suggestion. At this point whats another $50.00? Do you remember what m/c you have now? Part #? Thanks.
ARC grind the rear shoes to PERFECTLY FIT the curvature of the drums -- THIS step is critical to git a HARD pedal immeadeatly -- back when I was "workin" fer a livin - I NEVER did a drum brake brake job withOUT havin the shoes ARCED to FIT the drums PERFECTLY -- [ otherwise, they *will* "wear in" eventually BUT -- when *my* clients picked up their cars -- there were NO "soggy" pedals -- NOWadays -- you may have difficulity findin someone w a arc grinder -- thanke to the EPA and OSHA [ asbestos dust ya know ] ALSO, w a rough flat rasp file, "tip" the leading and following edges of yer pads and shoes @ about an eighth in 30 degree angle to elimanate squall and chatter
Yep bleeders on top and front pads are really good ones that have the edges ground. I'm going to have another look at everything on the rear tomorrow. Thanks for the suggestions.
Rocky. I removed and plugged the line from the m/c that feeds the front brakes. The pedal went rock hard. I then hooked it back up and re bled it. I then unhooked the line and plugged only the rear feed and it was soft again. So it sounds like the fronts are the problem. I am using the distribution block that came with the car for the ''fruit jar'' m/c to distribute the front brakes only. The line for the rear brakes comes straight from the m/c. On the fronts I have the m/c line feeding the distribution block and the right and left lines coming off of that. I have my brake light pressure switch tapped in the block also. I may try bypassing the factory block all together to remove that from the mix. Anyone think that a proportioning valve will help with my problem? I'm gonna fix this thing no matter how much it costs me or ticks me off! lol! Thanks.
The brake light pressure switch needs to be upside down or horizontal or it won't bleed and they can hold a lot of air. Better to put a switch on the pedal instead of using a pressure switch. The pressure switches also have a nasty habit of starting on fire when they leak.
Engine man. Thanks I'll give it a try. Maybe just remove it and plug it for a quick check. I have everything to put a switch on the pedal also. I was getting to that one of these days.
Pedal was soft only for the front? The master cylinder is too small to handle the fluid needs of the caliper pistons, try upping the master cylinder bore size. With hydraulics, the smaller the master cylinder in relation to the slave cylinder, the more you multiply force but you lose the movement. So whats happening is you're running out of movement and bottoming the pedal out. The larger bore will help move some more fluid volume at the cost of reduced pressure but that's why your pedal has a 6:1 or so ratio built into it.
I can't remember if you said you're using a residual valve for the front brakes or not and don't ahve time to re-read the thread but if you don't, the fluid will flow back into your master cylinder. This means you'll have to pump up the brakes to get the caliper pistons to come out enouogh to apply the brakes. A 2 lb residual valve is enough for disc brakes. If you already have one and are sure it is not malfunctioning, I'd get somebody to work the barke pedal while I looked at the calipers work. It could be the caliper mounts are flexing or moving in some way to cause a soft pedal. I'd be looking real hard at that residual valve...is it backwards? Check it out.
I tried residual valves front and rear and no difference. I have a 1" bore GM style m/c on there now. Seems like that would be big enough but who knows? HotRodder31 I'll look into that. The pedal does bottom out on the first stroke if I lean on it. It's perfect on the second stroke though. I've had a Ford Granada m/c on it for years but really never had great brakes unless I tapped the linelock button one time. That's why I went with the front discs , hoping for better stopping power. I cant find any specs for the bore size on the Granada m/c. It's a Cardone rebuild # 10-1602. I was thinking it was 7/8 so that's why I went with the GM 1" Bore. What next? 1-1/16? Thanks for the help guys. Rocky, I think that's a good idea [watching the calipers work] I'll try that tomorrow.
Are you using stainless steel for the hard lines? And are you getting air in the system? Stainless lines can be hard to get to seal and will let air in the system, but will not leak fluid.
Motor city is right on, the slightest leak will not always show up but will keep you from getting all the air out of the system. Stainless lines are bad for this, pumping the pedal once sure sounds like there is air still in the system.
Well, I took engine man's advice and removed and plugged the brake light pressure switch. The pedal came right up where it should be. I mounted the switch in a horizontal position , re bled everything and now everything works as it should. I do have a couple of stainless lines on the car and had really cranked on them because they gave me problems a couple of years ago. I put about 25 miles on the car tonight and it stops just fine now. Thanks guys for taking a few minutes to help me chase this down. I appreciate it! tommyd.
thanks for posting a follow up, so you mean the brake light switch position affected the level or sponginess of the brakes? When converting to disc, I usually add a mustang style brake light switch to the pedal arm.
It sure did. I have a factory electrical switch and pigtail for it. Just never seem to get around to it.
The Jalopy Journal
