Almost a disaster, a reminder,...and a question

Heard

Heard

Well-known member
Hi Folks. I've been working on my '36 trying to straighten out some wiring issues and other odds and ends. I've only driven this car a few times since I bought it several months ago. The brakes have been marginal at best in my opinion. The pedal seemed firm, but there was a lot of play at the top of the pedal. I'm talking 2 or 3 inches or maybe more.

So today I decided to start getting into this brake issue. Here is what I found after pulling up the plate on the floor and popping the cover on the master.

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As you can see, the right cylinder is pretty much empty. The other has about 3/8" inch of brake fluid. This could have been VERY EXCITING, but not in a good way. Especially since my e-brake is not hooked up right now.

So the reminder is to check those levels often unless you want a few moments of real excitement in your life.

My question. Actually 2 questions.
1. If one cylinder is empty like this, could that cause all of this play in the pedal? I haven't had a chance to fill it and check it again because....
2. I'm not sure what brake fluid is in there. I extracted a little and dropped a couple of drops in a container that had Dot5. The Dot5 I have is purple. Is all DOT5 purple? It didn't seem to mix very well. I then dropped a couple of drops in some DOT3. It was a little different color, but it acted like it mixed better. Is there a simple way to know for sure?

THanks!
 
It sure looks like DOT 3, but with it down like that, you may have a leak in that half of the system. If you haven't gone thru the brake system yet, then now is the time. Pull the wheels and drums and check the wheel cyls for leaks. Repair anything that is suspect. Pull the boots on the cyls and if you see fluid, they should be rebuilt or replaced. Check the lines for leaks or rust thru. Better to be safe than sorry when you're on the road. If you don't know what's in the system for fluid, flush it out completely and start with fresh fluid. Then, YOU know what's in there, no guessing.
 
If the hydraulic brake system was in working order and not leaking, the low reservoir level would not translate into a low or soft pedal. Naturally, if the system needed more fluid to compensate for worn brake shoes or a slight leak, you'd soon have that soft pedal as it consumed what was left in your reservoir.

Absolutely you need to check the system for any leaks....wheel cylinders, brake lines & fittings, brake light pressure switch if so equipped. ANY wet spots are a sign of leakage. Also make sure the MC cover isn't leaking at its gasket. If your reservoirs were filled at one time, the fluid has leaked out somewhere. It won't evaporate as you know.
 
drum brakes unlike disk brakes, the fluid will be forced back into the master cyl by the return springs on the shoes, and it will stay full unless there is a leak some where in the system, and it looks like there is a leak, pull wheels and drums look for leaking wheel cylinders, brake lines and be sure to check all metal brake lines, look for wet spots on them, the clamps holding them, and on the frame, a ittle more info on disk brakes, the master cylinder on disks will get low because the calipers dont have any way to pull the brake pucks away from the disk, so all the fluid pushed into the calipers stays there as the pads wear
 
For starters, how much free play do you have before the push rod meets the piston? A typical brake pedal ratio will be 6 to 1, so if you had, let's say, 5/16" free play you need to move the pedal 2" to begin to move the piston. Check the f/p and if necessary adjust for 1/16" or so.
Without knowing what your front brakes are but seeing a dual master and AN style fittings at the m/c ports I wonder, do you have disc brakes in front? AN (aircraft style hardware) is used on lots of modified cars and there is nothing wrong with it, I just made an observation. If that is the case then as the brake pads wear the piston and pad will move out so that the brakes are always "right there" so to speak. The pads are in light contact with the rotor even when you are not pressing down on the pedal. With this scenario your fluid level will go down, even though there is no leak in the system. When you put new pads on one needs to push the caliper pistons back and consequently the fluid level returns to normal. You can top it off if you do have discs, but when replacing brake pads be sure to take some fluid out first.
Dot 5 in the can will be purple in color, but soon after it is in use it will become clear, maybe with a touch of amber. I think Barry is on the right track, maybe flush the system and then you know what you have for sure.
 
Most Dot 5 I've seen yellows the more it is in contact with air and taking on moisture. Dot 3 stays a more consistant clear liquid but does get milky as it takes on moisture.
 
Great info, guys. Thanks!
Yes, I'll be going through the entire system in the coming days. I think I'll take the opportunity to flush it out and start from scratch. I think I'll also pull that master so I can measure the bore.

BTW, the car is all drum right now, though I'm considering going to front disc.

I was curious about the free play. I'll have to check it further.

Thanks again.
 
I would check to make sure the brakes are adjusted properly.If not this will cause you to have play in the pedal.That being said being out of adjustment has nothing to do with fluid loss.

Bill
 
Hmmm....my '36 has never lost any brake fluid.

Something Ford used to advertise "The Safety of Steel from Wheel to Wheel"
 
Isn't dot 5 silicone? Some of the silicone stuff I have had has been purple.

If it is safe enough to assume it is conventional fluid, I always use dot 4 in preference to dot 3. I did some tests on a clutch slave cylinder years ago and the dot 4 was better.

Top it up, bleed the new stuff through, really check properly for leaks, and check it weekly for a while until you can be sure it is not leaking out. Don't only check for leaks at the wheel cylinders, check every joint and fitting in the whole system.

There may have been a leak or some sort of bleeding problem when first installed and the PO fixed the leak without topping off the fluid. You never know what other people do, you have to start from scratch and sort it out to your own satisfaction. If you are in contact with the PO it wouldn't hurt to ask what fluid they used.

Mart.
 
Scott H said:
Hmmm....my '36 has never lost any brake fluid.
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Exactly. Actually, I should have stated that I noticed a very slight dampness on the bottom of the master. I knew it was leaking, but did not know how much or for how long. This is one of the reasons I didn't drive it much. I'll know soon enough if it is leaking anywhere else.


Mart said:
You never know what other people do, you have to start from scratch and sort it out to your own satisfaction. Mart.
Click to expand...

Good advice. That is exactly what I'm doing Mart. That is also the reason I was wiring in a fuel pressure switch and a few other things. I've also documented the entire wiring system the PO did and made a few mods. I'm now ready to go through the brakes and the suspension.
 
Mart said:
Isn't dot 5 silicone? Some of the silicone stuff I have had has been purple.

If it is safe enough to assume it is conventional fluid, I always use dot 4 in preference to dot 3. I did some tests on a clutch slave cylinder years ago and the dot 4 was better.
Mart.
Click to expand...

DOT 5 is silicone and while it will be purple when new once in use the color can fade and it may appear clear or slightly amber. DOT 5 is non-hygroscopic meaning it will not attract moisture from the air as will DOT 3, 4, and 5-1. The water that can accumulate in brake fluid will cause corrosion in the worst case, but at the very least can reduce the effectiveness of your brakes as the boiling point of the fluid will be lowered. D-5 being silicone will not attract water, but it will hold microscopic air bubbles in suspension and cause what some will describe as a slightly spongy feel. D-5 has no potential to corrode your brake system, will not remove paint if spilled on the car, and will last a very long time. That can be a simple test for Heard. If you put some of your brake fluid on a painted surface, say a spot on the frame or a suspension component and it removes the paint then you will know it is not D-5.

With the primary difference being the boiling point I'm left wondering what difference D-4 made as compared to D-3 in your clutch slave.

I used D-5 in my coupe over 30 years ago and to this day see no down side, other than it is more expensive and yes, I do have a slightly spongy pedal.
 
This is the first thread to make me feel good about my mechanical brakes.....glad you found it early.
 
It is possible the lower level was caused by more bleeding and not topped up.
Moisture on the master can be caused by a poor cover gasket.
As said, a complete check to your own satisfaction is the way to go.
Don't mix fluid.
 
ford3 said:
drum brakes unlike disk brakes, the fluid will be forced back into the master cyl by the return springs on the shoes, and it will stay full unless there is a leak some where in the system,...
Click to expand...

I believe I see residual pressure valves on the outlets of the MC? They maintain either 3, 5, or 10 psi in the system when the brake pedal is released. If a RPV with too low of a rating is used, excess pedal travel will result. For an underfloor MC I would use a 10 psi RPV.
 
You should assume the reservoir was filled at one point. That being said, where did the fluid go. It didn't evaporate, that's for sure.
 
As the brake shoes wear, the residual valves keep the wheel cylinders extended. With new shoes especially, they wear in and a lot of fluid will "disappear" -- it gets stored in the system. If you adjust the shoes, it goes back into the MC. But I'd surely check the whole system for leaks anyway.
 
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