68' Fury III Brakes

PlymouthFury3

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Hi everyone,
I recently replaced all the brake shoes, wheel cylinders, and the two brake hoses in the front. I bleed all the wheels and had no air. But, it really didnt have no pressure, but i still had some brakes. After driving on a dirt road (no traffic- country) to see how they acted. They were doing fine. But then, the brakes went right to the floor all the sudden and had no pressure. I had to throw it up in neutral to even stop. Anyway, i was wandering if anyone had any thoughts on what that can be. I orderd a master cylinder ( i would only assume that would be the reason). They are manual brakes, before this the pedal was pretty low before it would actually start braking. That was the reason for the change anyway. I appreciate any help. Thanks
 
Hi everyone,
I recently replaced all the brake shoes, wheel cylinders, and the two brake hoses in the front. I bleed all the wheels and had no air. But, it really didnt have no pressure, but i still had some brakes. After driving on a dirt road (no traffic- country) to see how they acted. They were doing fine. But then, the brakes went right to the floor all the sudden and had no pressure. I had to throw it up in neutral to even stop. Anyway, i was wandering if anyone had any thoughts on what that can be. I orderd a master cylinder ( i would only assume that would be the reason). They are manual brakes, before this the pedal was pretty low before it would actually start braking. That was the reason for the change anyway. I appreciate any help. Thanks
OK... I'll get you started.

First, there are two common reasons for a "low pedal", if that symptom is accurate. Usually it is out of adjustment drums or air has entered the system somehow(leak).

Second, many times folks unfamiliar with proper terminology claim a pedal is low when it is actually "sinking". A sinking pedal indicates a leak for certain.

At the end of your test drive, you definitely had a leak. Being a 1968 model you have a dual chamber master cylinder, so it is possible the leak is internal between the chambers (pistons). Unfortunately, I would be surprised if a master cylinder was your only problem.

Master cylinders are often damaged during bleeding. So when you get the new one, bench bleed it first (it should come with a cheap kit for this, and instructions). Then when doing a 2 man bleed, put a piece of 2x4 under the brake pedal on the floor. The block will prevent the helper from pushing the pedal all the way to the floor damaging the new master cylinder cup seals.

If your brakes are perfect, great, I would be happy to be wrong. I would careful inspect every inch of steel line for "scale rust"... big flakey rust means the line is compromised and my be the location of a pinhole allowing air back in. If nothing else you have lost thickness of the steel (strength). Also consider pulling the drums again, to inspect a wheel cylinder you should pull back the dust boots... if rusty inside, replace them... if even one drop of brake fluid drips out, replace them. It is normal for a slight dampness to be present.

If after all of that the pedal is still low, refer to the service manual for brake adjustment procedures. I find on many cars that the shoes are on backwards, the parking brake cables are over adjusted (preventing the proper adjustment until they are slacked and the star wheels are adjusted), and too many pros no longer know how to properly adjust drum brakes (until they drag a little).

There are many here who will offer help, let us know how this turns out.
 
Thank you for posting cantflip. I bench bleed the master (the air was def. out). I then inspected all the wheel cylinders, brake lines,fitings, bleader screws, brake hoses where they meet the metal line, etc. everything. I went to bleed the brakes again, and still no pedal at all. The master cylinder filled up with a foam in the rear cup (front brakes). So, i gravity feed to purge out the bad fluid. However, it is still cloudy. I let it bleed for over 1 hours, refilling about 5 to 6 times. Im pretty lost on what it could be. Im not a mechanic, but I did everything but change the brake lines themselves. Im just trying to get suggestions on what it could be now. The shoes are on right, and adjusted correctly. Im only 20 and have did everything in the car myself since i got it when i was 16. Motor swaps, drivetrain, replaced rear end, spindles, ball joints, torsion bars, etc. everything but the brake lines and master cylinder, With advice . So, im not trying to be cheap to take it to a mechanic, or "attempting to put the car in a dangerous position on the road, not knowing what im doing lol". Just trying to do it myself "pride". So, anyway thanks for any advice you can provide. Ill take some photos. Maybe...... that might help.
 
if you are bleeding it thru the bleeders slow like that, put a hose on there and catch your fluid again so you can reuse it, just keep it real clean. if you are bled, and you still cant build pressure, there is a hole somewhere. especially if you still get cloudy / bubbles /etc.

try not to die -

- saylor
 
if you are bleeding it thru the bleeders slow like that, put a hose on there and catch your fluid again so you can reuse it, just keep it real clean. if you are bled, and you still cant build pressure, there is a hole somewhere. especially if you still get cloudy / bubbles /etc.

try not to die -

- saylor
Sorry saylor, you should never reuse the fluid. DOT 3, 4 and 5.1 absorb moisture and are fully saturated within an hour's exposure to air. The idea of using a bit of hose and a catch bottle will cut down on the mess and with a clear hose help you see that air is coming out.

BTW... parts store fluid is usually lower quality than the factory fluids (lower boiling points), the DOT designations are about more than the boiling point... F$@d Heavy Duty DOT 3 exceeds DOT 5 minimum boiling point standards and is favored by some SCCA folks.

There is an shade tree method of putting the hose deep into the bottle and pumping the pedal for a one man bleed, the fluid in the bottle prevents you drawing air, but you are not keeping the new fluid as pure this way (hence the "shade tree" part).

There are one man bleeder screws available that also allow this method, but contain a check valve to prevent drawing backwards into the system. I have never used them, but think they are a neat idea.
Thank you for posting cantflip. I bench bleed the master (the air was def. out). I then inspected all the wheel cylinders, brake lines,fitings, bleader screws, brake hoses where they meet the metal line, etc. everything. I went to bleed the brakes again, and still no pedal at all. The master cylinder filled up with a foam in the rear cup (front brakes). So, i gravity feed to purge out the bad fluid. However, it is still cloudy. I let it bleed for over 1 hours, refilling about 5 to 6 times. Im pretty lost on what it could be. Im not a mechanic, but I did everything but change the brake lines themselves. Im just trying to get suggestions on what it could be now. The shoes are on right, and adjusted correctly. Im only 20 and have did everything in the car myself since i got it when i was 16. Motor swaps, drivetrain, replaced rear end, spindles, ball joints, torsion bars, etc. everything but the brake lines and master cylinder, With advice . So, im not trying to be cheap to take it to a mechanic, or "attempting to put the car in a dangerous position on the road, not knowing what im doing lol". Just trying to do it myself "pride". So, anyway thanks for any advice you can provide. Ill take some photos. Maybe...... that might help.

"Only 20"... LOL, Lots of us somewhat older folks in here really appreciate any members of the younger generation who have found their own connection with these cars. I used to be in that youngster category... somehow it doesn't stay that way. Knowledge and skill doesn't come with age, those things we acquire along the way with some conscious effort. We have a number of younger members who could school many of the older folks. Maybe some of them will reach out to you in time... welcome again.:welcome:

I'm not quite 50, I have been working in the auto repair industry since I was 17... and I learn from this group all the time. For some here, I am still a youngster.:rolleyes:

Back to your brake problems... I have a few questions just to clarify things.

1-"I bench bleed the master", was this a new master cylinder, or the old one. Chances are good that the old one was damaged... but that doesn't fully explain why the air (foam) happened... it may explain why you had no pedal. Also cloudy fluid may be an indication of fluid that was not changed for too long (every 2-3 years). The fluid holds small amounts of sediment in suspension... the sediment is mostly microscopic pieces of the rubber components like seal and hoses. If there is too much sediment and it settles... there is often a "domino effect" of failures as seals get dragged across it during repairs (moving outside of their former range). Brake fluid flushing (NEW ONLY) BEFORE starting repairs Might prevent this... but it is pretty common.

2-"The master cylinder filled up with a foam in the rear cup (front brakes)." The foam is a sure indication of air. Here is the tricky part, you could have a leak at the rear seal of the master cylinder. In your case with manual brakes, you will need to look for a small amount of fluid coming down the bulkhead under the dash. You might also catch a sign of leakage on the engine side of the bulkhead (it doesn't prevent fire from spreading... it is not a firewall).

You can look at a 1968 service manual here, I am, we all need to use the book to help us keep things right (nobody knows it all).
MyMopar - Mopar Forums & Information - Service Manuals
#3- This is very important to note... every once in a while, a leak doesn't put out much if any detectable fluid... in these cases, the system draws air from the leak, but doesn't give a good clue as to where it is coming from. The possibilities I can see for your front brakes are the master cylinder, the wheel cylinders (front), the steel lines (especially the parts that have a spring looking stone guard on them), or the pressure differential valve/switch (called the hydraulic system safety switch in the 1968 factory service manual).

#3a-There is a good chance that the "hydraulic system safety switch" has been activated (page 5-16 in the FSM). This switch is "supposed to" activate the red brake light on the instrument panel AND block fluid loss to the half of the system that lost pressure. They don't often mention the blocking part, but your switch may need to be reset at some point. The clues are that the red light is on and/or the front brakes don't bleed as freely as the rear. (Note: once the brake pressure has been reestablished, the switch can often be reset by opening a bleeder on the good part of the system and pushing the pedal hard enough to cause it to move back to center... This can be tricky to do. Some allow for a mechanical reset... I don't see that option here. If the part is available and the light is on, the FSM recommends replacement.)

#3b- If the master was not replaced, you may need to replace or rebuild yours in order to get enough pressure to move forward with this diagnosis. To test the master cylinder for leaks (internal, or sucking air externally) most parts store have a large selection of bass/steel fittings. You could take your master cylinder with you to assure you get the correct size, and buy 2 fittings for blocking the "flare nut" ports... they will have a divot(recess) to clear the tube seat in the master cylinder line fitting. Bench bleed the master and install the plugs, you can bleed any little air by loosening the plugs at the bench while depressing the pistons. Install the master onto the car and pump the pedal, it should be very hard and high and not sink... Proof the master is not the cause. If the pedal sinks or draws air, you need a master cylinder.

#3c- If you can get the lines to bleed good enough to apply pressure, after the master cylinder has been proven good, you place the 2x4 block flat under the brake pedal to protect the master and stand on the brake with both feet and push as hard as you can. I have had several times in my career that a hard to find brake line leak was found by me doing this... it often destroys the master cylinder though. It's also fun to watch management, service advisors and customers poop themselves when you blow out the brake line. You should never be able to blow out a double wall steel line in good condition from the brake pedal... imagine a panic stop.
If you can't get enough pedal height to do this, you might try leaving the plug in the rear circuit of the master cylinder (might work).

Finally, I have gone by the assumption that you carefully checked the wheel cylinders for fluid inside the dust boots... if there is any doubt... that would be something to recheck. A single drip is too much, a little moisture is normal, but you shouldn't gain a lot of moisture while testing either. Wheel cylinders are usually cheap, you will have to decide what's worth the effort here.
 
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