I just did a disc conversion on my '62 fairlane and upgraded to a dual M/C for a '74 Maverick, I've bled the brakes, bench bled the master and I can pump the brakes and get plenty of pedal and if I keep pressure it holds, but when I take my foot off for a few seconds it goes right back to the floor when I put my foot on it. What gives? Sent from my iPhone 4 using TJJ
Bump. Out in the shop about to pull my hair out. Any help is much appreciated. Sent from my iPhone 4 using TJJ
I've bled all 4. I'm letting it gravity bleed right now. This one has me stumped because I would think if it's a bad MC that I would lose pedal with pressure on it. But it doesn't go until I let off and wait about 10 seconds. Sent from my iPhone 4 using TJJ
Hmmmm ... Are you sure the rod from the brake pedal to the MC is long enough ?? Have you got a equal lizer in the line ??? Excuse me I cant spell worth a shit but I am a pretty good mechanic ...
Some questions. How are you bleeding? Does the master fully bottom out before the pedal hits the floor? Did you check for a residual in the rear brake master port? (I would add a 10 lb external valve if needed, and only to the rear drums) Did you install an adjustable prop valve? From your description, there's a good possibility you've still got air in the system, assuming the rears are adjusted properly. If the master cylinder is a rebuilt, I would take it apart and check for any damage or foreign material, common on rebuilds.
It's a new master, adjustable prop valve to the rear. I'm pumping the brakes until the pedal is hard and crack the bleeder screw until the pedal hits the floor. I can't recall exactly if the MC bottoms out before the pedal hits the floor Sent from my iPhone 4 using TJJ
Malpass, do NOT let the pedal hit the floor when bleeding, that's 1. OK buddy, listen if you can see the chambers or have someone watch the chambers does this. Only push the pedal until you see the bubbles rise in the far chamber of the M/C, OK. Hold until the bubbles stop rising. Now when you let up, stop at the top or released position of the pedal and count for a 2 count. Also do not pump too fast, alot of people do that, wrong, pump slow. When you bleed, start at the right rear, then left rear, then right front and finish at left front, good luck, TR
I think I just found my problem... I was supposed to use the original pushrod not the one that came with the new MC Sent from my iPhone 4 using TJJ
Hi ..Your master cylinder is not matching the volume of the wheel cup capacity..had same problem with a disk conversion on a 56 fairlane...brakes were fine with early mustang calipers...but when I changed for later model caliper with a 1/8" bigger caliper piston the brake pedal when straight to the floor ..you could pump it up with 2 strokes of the pedal ..leave it for 10 seconds...then reapply pedal straight to the floor...had to use a 1 1/4" bore master for more volume to the wheel cylinders pistons....Doug
Well yea, if the pushrod length is too short, you wont get full travel, and the pedal will sit too low, if too long, the m/c will never come fully back making bleeding impossible. If the length is the same, you still have air in the system, and if the rod is too long you probable still have air anyway. Sometimes it can be a bitch to get all of the air out....
Also one of those things to remember make sure you have the calipers on the right side with the bleeders facing the proper way. I mistakenly swapped the calipers when putting new ones on my truck and scratched my head for a couple hours. Instead of swapping them and re-bleeding I just pupped out the bolts and laid them in a pan to gravity bleed. Sounds like you got it though.
You do not want to pump the pedal while bleeding. Slowly full stroke the pedal while cracking a bleeder. The master cylinder pistons HAVE to be fully stroked to attain a good bleed, the reason the pedal cannot bottom before the master. Using a short length of clear Tygon tubing running up from the bleeder, and into a container, will give good visual of any air. When the fluid slows, close the bleeder and repeat a couple of times. (It doesnt make any difference which brake you bleed first or last on a dual system). Take your time and go around the brakes at least twice, or until NO air is present in the Tygon. You will want to perform a high pressure leak test once you have a decent pedal. Stand on the pedal (at least 150 lbs force) for 10 -15 seconds to be sure of no pedal loss, leaks or weeps. Use isopropyl or denatured alcohol for clean up on all fittings and fluid spillage.
I tried everything I've got to get the new pushrod out. I need a bench vise. Gonna give it another go tomorrow. Sent from my iPhone 4 using TJJ
I got a mc from Speedway and was,nt any good same problem,got new one from NAPA Mustang fixed the problem.
One reason it's better to get a power brake master cylinder- no attached push rod to deal with. Another is a deeper push rod bore in the primary piston which makes a custom installation easier and safer.
Sorry, this is 100% untrue. The pushrod bore of a Powerbrake M/C has very little concave or deepness to its design. It is designed to have the pushrod supported by the passage thru the booster, this is what supports the pushrod in a Power Assisted M/C arrangement. To use one of these M/C without a booster supporting the pushrod is extremely dangerous and totally irresponsible. No booster, use only a M/C made for a non power assisted brake system. TR
What do you base your information on I base my factual comments on many years of hands-on experience, primarily with FoMoCo/Chrysler booster/masters. All the vacuum booster push rods that I ever worked on are much smaller in diameter than the booster outlet-they have to be to allow the rear master cylinder body to enter into the booster. Most/all booster outlet push rods can be easily pulled out of the booster. The push rods HAVE to have the master cylinder contain them with a deep bore. Manual masters typically have the push rod captured or retained into a shallow bore. What you state above is 100% totally wrong.
I like that new bleeding tool I saw on Gearz the other night ... You pump brake fluid in at the calipers or drums up to the master cylinder ... No pumping brake pedal ... One man can do this with out any help .... It would be easy to make one , all you need is a little hand pump a bottle of brake fluid and 1/4 rubber hose to connect the pump to the caliper ... Thanks V8 Bob for letting TR know hes not the onley one thats ever worked on a car ... He has no respect for another mans opinion ...
Like junkyard said. Make sure your drum brakes are adjusted. Return springs will pull the shoes away from the drums, depending on design. You want to create drag then just back off.
You said EXACTLY the opposite in your post that I quoted, now your back pedaling and changing your story. Your original post could have gotten him killed. This is the end of this conversation, here is a clear and consise picture of what might save his life or killed him and innocent people around him. The deep hole is the non-power assist M/C, the shallow one is the Power assist M/C. PERIOD. Your advice will get someone killed and it is wrong. Look at the pictures and admit you were wrong, its not that hard. I mentioned NOTHING about pulling the pushrod in or out, and didn't quote you on that post. Read that part twice so you understand. Please check your facts, and read things twice before you start this drama again.
You too are some pair, misinformation, and good ol boy education, and advice that will get someone killed. Respect is earned here on this forum, not in your gravel driveway, under a car on cinder blocks, with a hammer and a screw driver for a chisel. Opinions are one thing, wrong information regarding brakes are another. I posted a clear picture to explain once and for all, what you good old boys dont understand or just dont want to understand, you were wrong, and its a darn shame you cant admit it, and are too stuborn and ignorant to learn from it. Hide behind your computer and slander someone who actually has a very formal education, instead of learning from him. Your right about one thing, I have NO respect for information that is false, then gets spun into something that remotely ressembles what you thought you should say to cover your mistakes, and ultimately has the distinct possibility of killing the person reading it, and GOD forbid taking your advice.
Lets remind the others of your opinion/advice that you gave another member, and I commented on, that you have since had such a dislike for me. Your opinion and advice was for the poor guy who just completely rebuilt his first engine and had a totally dead #1 cylinder. You do remeber right? Your opinion and advice was to start it back up and keep running it until it I quess majically fixes itself. A completely rebuilt and freshly machined engine, start it up and keep running it with the totally dead cylinder. And I'm the bad guy.
As said above adjust up the rear shoes so that there is a light drag. If they are not adjusted well the return springs pull the shoes back away from the drum and you have to pump it back up to take up the slack every time. carefully check the location of the bleeder screw in the caliper. It has to enter the caliper at the very top of the caliper or you will have trapped air and never be able to get it out. Oft times they can be mounted incorrectly and the bleeder screw is not at the tippy top trapping air.
I had the new front calipers reversed. Thanks for all of the advice... And entertainment Sent from my iPhone 4 using TJJ
Yes I remember the engine you wanted the guy to tear back down when his choke was closed causing his engine to flood ... Sure glad he didnt listen to you then ... You think just because you have built a race engine youre the onley man on the planet that has ever turned a wrench ... Ive seen youre type before , always bragging on youre self patting youre self on the back ... You should keep youre big mouth shut when some one like Bob and I are trying to help a guy fix a problem with his car ... But youre a know it all ... You think you and onley you know how to build an engine ... Bull Shit ... You think you and onley you have an education ... I got my education while I was off fighting for youre freedom 1n 1969 ... Guess I dont get any respect for that either ... Oh buy the way Ive been working on cars for 40 years and havent got any body killed and I dont think Bob has either so why dont you keep youre 2 cents to youre self when were onley trying to help a guy out ... You got youre way of doing things and we got ours ...
The Jalopy Journal
