UPDATE: ARRGGH! Need Help! Brake Issues

Hey fellas, pretty frustrated tonight. Running 1939 hydraulic brakes on my A tudor, new lines, new wheel cylinders, new dual Master Cylinder. I bled everything oout and got a firm pedal but it faded, I found out I was supposed to add 10psi residual valves on both front and back lines close to the Master Cylinder. So I did this, made sure they were facing the right way, ****oned up the system, and bled again, pressurized, no leaks and no air it appears. Get in pump the pedla its firm. I hold my foot on it for a couple minutes, stays firm, no fading, cool. WELL...as soon as I take my foot off, 3 second, than depress again, all of the beautiful pressure is gone. I pump it twice its back. So WTF?

I bench bled the MC, and have double checked almost everything else.

WHAT AM I MISSING? HELP!
Could it be a bad MC, or something else?

 

I am leading towards MC, its a speedway unit (I know probably not the best quality) that came mated with pedal and MC.

skid, your comment was my thought as well, but is that possible? Where and how can I check?

 

Make sure your shoes are adjusted right first.

 

Mine does have a larger reservoir for the front, is that an issue? I have a 10psi RV is both front and back as specified and no leaks. Didnt know reservoir size could affect the system.

By the way, brakes all slightly drag, so they are adjusted.

 

The guys at Speedway said I needed residual valves with this one.


Specs Below:
Designed for a clean and simple install onto Model T, Model A, and 1932 Ford frame. The included 1" bore remanufactured master cylinder is suitable for 4-wheel disc or disc/drum brake setups. The outlet ports are 3/8"-24 IFF. The bracket can be bolted or welded to the left frame rail (boxed or stock).

Kit includes a dual feed master cylinder, frame bracket, and a steel pedal arm w/ pad that can be easily modified for driver comfort.
Note: Will NOT work in conjunction with the factory clutch pedal. Intended for use with an Automatic Transmission.
916-31926 Instructions (PDF)
Learn more about selecting the proper master cylinder for your vehicle by reading our tech article. Brake System Selection.

 

Same size dual reservoir brake master cylinders, power and manual, were used on drum-drum from all manufacturers of the conversion period from mid-60s to early-70s when the shift was made from single to dual brake systems and drum-drum to rum-disc. Many are still available through parts stores at better prices than the popular ones.

 

Skid,
So if I pick up a 67 Mustang MC, can I leave the Residual Valves in the line, or should I take them out and rerun that section of line?

 

Here is what summit shows for a 1967 Mustang MC
http://www.summitracing.com/parts/dhb-m71248/applications

It appears to have two size reservoirs as well.

 

If the master cylinder was for drum or drum/disc combination, it should have built-in residual valves in the outlet port . What car do you have? If it's an older car and you're using "through the frame" connectors for the brake lines, it's been found some of those can trap air inside the barrel of them.

 

Rocky,
Thats a thought, never considered that, the guys at Speedway said it needed residual valves (OR THEY JUST WANTED TO SELL MORE PARTS
I have a mustang MC like a guy suggested above, if I use it, do i leave the valves in or should i remove and rerun the section of line?

 

I've posted this video before for the other lister having brake problems. This episode of Muscle Car explains underfloor master cylinders pretty well. I had a problem with my dual master conversion too. Ended up being a bad rebuilt master from the kit. I also made sure I bled the master a lot before installing.

http://www.powerblocktv.com/episodes/MC2013-02/oldsmobile-restomod-returns

Go towards the end of the video for the brake section. Good luck.

 

I must have a bad Master Cylinder, I have done everything else as explained. I will switch out and update you guys.

 

Before you give up, try bleeding it a joint at a time. I did this for my truck as I replaced all the lines, hoses, cylinders etc. I started at the master and since it's under the floor, I could grab the brake pedal from underneath and pump it and hold it down while I cracked the lines to the master to remove any air. Then moved to the next joint etc, until I couldn't reach it anymore. Then got my daughter to help me with the rest, or my wife. They're good sports about it too. Good luck.

 

Didn't you say you were using drum/drum?

All the apps that you listed for that M/C are for DISC/ drum

????

 

The application says drum/drum as well in the catalog, also techs tell me i have what I need. Going to go back through everything as recommended above starting with MC, cap it off and see if same issue, that way I can definitively rule out the MC or not. Then head down the line.

 

This is what you should have, a Ford drum-drum dual master cylinder. Both reservoirs are the same size and it has residual valves built in. Works well with early Ford Lockheed brakes. You may also find that the brake system will work better if you use 1/4" lines (like Ford used originally) due to the size of the Lockheed wheel cylinders.

 

Hey Rich,
You got a part number?

 

It is a Bendix 11485 master.

Lists for a '67 Mustang with non-power front and rear drum brakes a**** other applications, like skidmarks recommended.

 

i got mine from www.Rockauto.com and have not had a problem with it.. i also read threads that say leaving the residual valves in line won't hurt nothing..

 

also, the reservior closest to the mounting bolts is for the front brakes.. you will see that when you bench bleed the mc, that port will squirt first

 

Update: Havent had much free time in the garage this week, but have been digging deeper until I can start replacing things.

Pedal status: upon getting into car, depressing pedal the first time is weak, than pump 2 and three become firm and hold firm. as soon as I release, the next pump is weak again.

So...I removed the cover an watched to see what is actually happening. This first weak pump is actually pushing a strong stream of fluid out of the hole in the bottom of the reservoir, the second and third pumps do not produce a stream and the pedal is back. Let pedal return, remove foot, than repeat...weak pedal and stream shooting out of hole again.

So is this fluid getting past piston or something, bad MC, or something I am not understanding?

 

Did you check the brake shoe adjustment?

 

Ok let me splain sumtin. If you pump up the pedal and it holds firm I really don't think you have a MC problem. What is happening is after you release the pedal the springs in the brake ***embly are pushing fluid back from the wheel cylinder into the MC. This is what is causing your soft pedal on the first push. You say you are running 39 brake ***emblys? well these take a lot more adjusting than new type brakes. Twer it me I would adjust both the top and bottom until you can't turn the wheel then check pedal again. If pedal is good with 1st push then back off adjustments until wheel will turn then check pedal again. and work from there.
Good luck

 

I would try what Fuzzy Knight suggested. If it pumps up like you say you either have too much travel in the shoes, causing it to use all the capacity of the master before the shoes get tight. Or mis matched size on master and wheel cyl, again causing the master to run out of volume before the shoes are tight. Or you still have some air in the system which is using fluid volume to compress the air instead of moving the shoes.

 

UPDDATE:
The Master cylinder is good, ruled that out, also ruled out the front part of the system, so it seems the issue is in the back half. No leaks, so air has to be trapped somewhere. There is a highpoint in the system over the banjo where I have a T that connects the flexible hose and the rear lines to the wheel cylinders. The other thing is the pressure brake switch, that could be a pocket. Guess I will keep pushing fluid through it, any other ideas?

 

Keep at it !! One section at a time. Soon all will be well.

 

Ok, so took everything apart for inspection, planned to adjust the bottom pivots, read to posts above, I dont see how there is any adjustment on these, basically there are two pivots at the bottom that come through the backing plate, have a small cap or whatever on the back side and the two cotter pins on the inside. What is adjusted? Am I missing something, these pins dont go into any new positions, they just allow the shoe to rotate right?

 

Those are not '39 brakes like you said in your initial post.

They are the later ones '42-'48.

The bottom anchors are not adjustable on this style of Lockheed brake, take the retainer plate off and make sure the pivot bushings are in place and free to slide in the oblong hole in the shoe.

 

read through the thread hope i didnt miss this but check the residual pressure valves and make sure that the flow is in the right direction it does matter

 

The only adjustment on those is the two upper bolts on each side, if you turn them you can see the offset in that washer looking thing, it will push the shoes out or give them more room.