61 brake issues

[Notar61]

I have a 61 sedan, drums on all 4 wheels. This thing is ready to get back on the road but the only thing keeping her in the garage are some brake issues. I decided to stick with drum brakes, but I did do the dual bowl master cylinder conversion. Did all new lines, new wheel cylinders, new brake shoes, and new drums.....but good braking eludes me. The thing I seem to be fighting is excessive brake pedal travel and a soft brake pedal. The brakes work, but not until the pedal is on the floor and sometimes you do have to pump the pedal a few times for the brakes to catch. But that good braking power seems to go away after about 10 seconds and then you have to pump them again to stop. I have tried the following: excessive brake bleeding(both gravity and traditional types), adjusting the brakes on all 4 wheels for drag, and playing with the bolt that connects the master cylinder pushrod to the brake pedal. Any ideas? I'm at wits end trying to figure out what is going on. Only thing that I can think of is if I got the wrong size bore on the dual master cylinder I used for the conversion. I believe I got one with a 1" bore....it would be one that would be compatible with a 1967 mustang with drums on all wheels. Also I was reading about residual valves too....would it help to add some of those to my brake setup?

I'm open to any suggestions! Thanks!

[redfalken]

If you're not loosing fluid it seems like there might be some stubborn air in the system somewhere. Did you bench bleed the new master cylinder before installing? And did you use your original push rod and not the one that came with the new master?

And be sure to bleed starting at the furthest away from the master cylinder which would be the rear passenger side. Then do the rear driver side, front passenger, and lastly the front driver side.

Not sure how much experience you have with brakes so I'm asking some basics to begin with.

[Notar61]

Yeah I did re-use the old pushrod and I actually bench bled the master cylinder twice since I thought it was the source of the problem at first. Should of mentioned that earlier sorry. I think the master cylinder is fine. I plugged both port holes and the pedal is as hard as a rock.

[Notar61]

Now I am thinking I used the wrong master cylinder. The fluid bowls in the master cylinder are not the same size, so this makes me think I got a master cylinder for a disc/drum setup. I am keeping the manual drum brakes on all 4 wheels, so maybe this is why the brakes don't seem to be working right? Has anyone on here done the dual bowl master cylinder conversion and kept manual drums on all 4 wheels? If so, what master cylinder did you end up using? I used the Bendix 11485.

[Notar61]

Just to be clear:

The master cylinder I used looks like this:

http://images.cjponyparts.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/b/m/bmc23_1.5.jpg

Do I need to use one that looks like this?:

http://images.cjponyparts.com/media/catalog/product/cache/1/thumbnail/9df78eab33525d08d6e5fb8d27136e95/b/m/bmc32_1.jpg

[Luva65wagon]

[Your name],

No pedal is not going to be due to the M/C you used. You might notice brakes dragging, unequal application of brakes when in an emergency stop, or poor or excessive braking power (based upon the bore size as it relates to the wheel cylinder/drum sizing) but generally the only thing that can cause the brakes to not pump and hold is air being in the system - somewhere. Or the plunger is not going back all the way to uncover the hole and let the fluid fill the bore again on each push.

Keep in mind that a different size reservoir doesn't always mean differing bore sizes. The larger bowl is to minimize fluid temps as a disc heats fluid more than drum. The M/C may have a residual valve built in too, but this won't stop you from getting pedal.

I recall installing a dual (drum/drum) M/C on a members Falcon a few years ago and having one heluva a time bleeding brakes. Apparently, even though I used the original plunger in the new M/C, the plunger was being pushed about 1/8" of an inch all the time. It was not possible, really, to eliminate this; so I installed a couple very thick 3/8" ID washers between the M/C and the firewall to let the push rod "float relaxed" in the bore of the plunger. Problem solved.

Granted, the dual drum/drum M/C on a Mustang is supposed to be two identical sized reservoirs, which means you do have the drum/disc M/C. As I said, I don't think this is keeping you from getting firm brake pedal. On my 66 F100 with drum/drum I installed a dual M/C with differing reservoirs. It was a M/C I had and couldn't return it to anyone. I was more interested in getting the truck from outside (my carport) to the garage, which was down one hill and up another. As it turned out I did bleed the brakes on this truck (everything new at that point) and moved it over to the garage... and have driven it a lot since then with no apparent issues so far.

So check to make sure when you connect the plunger to the brake pedal you have about 1/8" of slop as opposed to 1/8" of pressure. And if all else fails, get the correct 67 drum/drum M/C and try it.

[Notar61]

Roger,

Thanks so much for all the info. I think I'm going to get the right drum/drum MC, install it, and see where that gets me. If it still gives me fits, I will look into adding some washers between the firewall and where the master cylinder mounts. And I will give it another good round of bleeding as well. I appreciate all the sound advice. Oh and my name is Andrew by the way!

[Luva65wagon]

Andrew,

Sounds like a good plan to me. You might try the washer thing first, just to make sure the plunger isn't being prematurely plunged. If you loosen the bolts and the M/C moves away from firewall and light pressure doesn't let it sit flush without forcing it against, then shim it and see what happens.

Good luck!

[Nathan289]

On my 62 the bolt on the pedal where the mc pushrod attached was cam centric. Meaning you can adjust push rod length by rotating the bolt..

Won't solve the pumping problem, though.
Sounds like a bad mc if its been bled propperly.

[Luva65wagon]

That's true Nathan, unless it is rotated and keeping the plunger from going neutral and is plunging the piston when it is supposed to be released. I took what Andrew originally said re: "playing with the bolt that connects the master cylinder" to mean he rotated this to correct a over-pressed push rod. But maybe he wasn't aware that's why it has a cam?

I'm not 100% sure that's why it has a cam. Maybe Ford just wanted to allow adjustment to the pedal height? I don't know. In 1965 they moved to a solid pin on the pedal shaft.

But if the M/C won't hold pressure, and if it's not air in the lines or M/C, then the pistons are letting all the fluid move past them or to just move in and out of the bowls. Or it's not suctioning fluid from the bowl on each pedal release.

If fluid is moving past the pistons, the fluid level will drop and run out the back of the M/C.

[Notar61]

Hey everyone! Wanted to report back. Yesterday I went to my local parts store and got a dual bowl master cylinder for a 1967 mustang with manual drum brakes on the front and year. Pulled the old one off and stuck the new MC on there. Re-bled everything really good and it seems to have fixed my problem! I finally have pedal resistance and it stops way better now. Just wanted to let everyone know. Thanks so much for all the help and ideas on this!

-Andrew

[dhbfaster]

WOW...very interesting. So is it because before you didn't have the M/C for all drums? or is it because the one you had was defective?
I know, probably doesn't matter...but I'm a root cause get to the bottom of it guy....I will keep wondering and wondering...:WHATTHE:

[Notar61]

I think the old master cylinder was okay. I plugged both the ports and was able to get a pretty rock hard brake pedal. I think the problem was just that it was for the wrong type of brake setup. I'm not for sure, but do disc brakes require less pressure or PSI to activate than drum brakes? Maybe this is why the drums on my car never seemed to be "all the way" engaging with the old master cylinder? All I could ever get was no pedal resistance and pedal travel all the way to floor. Not really sure.....but I'm just glad that the new master cylinder seems to have fixed the problem!

-Andrew