hey man thanks for the reply. the bowls were not filled prior to starting the truck, i have not yet checked the plugs, but i will do that tomorrow.
also ill look more for the leak area, but i so far cannot find it. is the smaller/front chamber the front or rear brakes?
its killed my wallet but i love my dentside
thanks again

 

'rear wheel cylinders, and the block on your rear axle"
do you have a picture of this? im not sure what you mean by "rear wheel cylinders" and "block on your axle" thx

 

i thought i replied to the above messages but i cannot see them.

I still havent managed to find any leaks or anything yet, its so frustrating haha. is the smaller chamber the front or rear brakes?

 

by small front chamber your refering to master cylinder then yes it for rear brakes

 

I am unsure if same,,I have been told there is a difference

 

Look at the pic, 6068 is the transmission mount.

I've already looked up the part number (D6TZ-6A023-A), it has a gazillion different applications for misc 1976/79 F100/250 2WD & F350 with 300/302 (except F250/350)/351M/400 engines.

351M/400's are 4 M/T's, but others could be C4's or M/T's. I'll list all the applications when you verify this is the part you need.

 

so i can confirm there is a leak. i put a foam pad underneath where the master cylinder is, which is adjacent to the front wheel, and filled the reservoir up with fluid again. pumped the brakes, and the front reservoir was empty, and on the matt there was a sizeable pool of fluid that had fallen. (this is all within 30 seconds, so i didnt leave it for a while or anything). I cannot tell whether it is from a line, or from the MC itself, or whatever. and im not sure how to go about finding out. when its light out and i have a chance ill upload some pictures of what i saw.
any suggestions or ideas? thanks

 

yea, thats what i meant.
ive been told in the past that my drum brakes (rear ones) arent as important as my front disc brakes, and that unless im hauling a load, i shouldnt need ot worry much about them, so once its otherwise running, would i be able to limp it over to a friends house so he could do that particular repair? i have yet to be able to locate the leak, but the front chamber is the only area that is leaking

 

Pretty sure that's what he was referring to,,do you know if there is a difference in transmission crossmembers from automatic verses a standard transmission ?

 

If it's the master cylinder, then it will be leaking out of the back of the MC into the booster. You might see a trail of fluid running down the booster, under the MC. You could remove the MC bolts and pull it forward some, to see if it's leaking out the back.
But I still wouldn't trust that master cylinder on a public road - at least not one with people around...

Some rust on brake lines is OK, but if they look really crusty, then they're a leak waiting to start.

 

Yep, could happen. But luckily(?) when these diaphragms let got they often squirt fuel outside through the vent instead. Right on to the exhaust manifold!
Not sure who was thinking what that day...

Don't believe that! That is just someone misinterpreting reality. I can see where that line of thought comes from, but I still say it's wrong thinking.
Yes, under normal braking action the rears do less work than the fronts. But what if the fronts aren't working? I'd say your rears would be pretty darn important at that point!
So you ALWAYS NEED, AND SHOULD ALWAYS WORRY about your rear brakes. Because they're part of the system and any brake that is sub-par or has failed is grounds for grounding the truck until you find the problem.
A seriously leaking component is just such a condition.

How far is the friend's house? Your results may vary but my answer is "maybe, but most likely not" to that question. If the system is that bad as it seems to be, it might be just a matter of time before the fronts fail, or the master fails, or something else lets go and leaves you without any brakes at all.
I would not do it then unless it's right around the corner or you have no other cars to deal with in a more rural area with plenty of runoff area near the road you'll be on.
Around here I'd never even take it out of the driveway in that shape.

The earlier mentioned wheel cylinders are inside the drum brakes, out of sight. You'll have to take the drums off to see if they're leaking. The good news is that eventually they usually show by the fluid leaking out of the bottom of the drum on to the wheel or the ground. But if you don't see that, it may mean the leak is elsewhere.
But you might not see a leaky wheel cylinder right away. At this point I would pull the drums off anyway. You need to go through the entire braking system it looks and sounds to me.
Too bad, and not a little bit of work. But it has to be done.

Good luck.

Paul

 

Oh, and as mentioned the leak could be at the back of the master and leaking into the booster. You won't see it unless it starts to leak out and drips. Which it eventually will if it fills things up.

It's a pretty simple and straightforward system actually. Just follow all the lines and look for leaks. If it's not in the lines, pull the drums off. If it's not in the drums, pull the master off.

Frankly, budget or not, I'd simply replace the master and booster and then plan to do the same to any wheel cylinders and maybe even the front calipers.
It ends up being a lot of money when it's all added together, but it's all such a critical part of your safety now that you're driving an old truck that you have to do it. It's just been sitting way too long with questionable components.

Paul

 

so if the leak was my master cylinder, then would both reservoirs be losing fluid? or at least teh rear one? the smaller front reseroir is the only one losing fluid.

 

That's an excellent question. And I'm certainly not sure of the answer.
Generally speaking, since the two reservoirs also have their own pistons and seals to work from, either one can cause trouble independently. But since anything leaking from the front reservoir to the back of the master and into the booster would have to go through the rear piston and seal too, then yes, I would think that you'd be losing fluid from the rear reservoir as well.
But I'm not intimately familiar with the inner workings of a master cylinder, and if there are other channels for the fluid to leak past the rear cylinder through.
Just that it does not seem like there would be anything like that.

So that leads back to the fact that you must follow the components one at a time until you find the leak.
Have you looked down on the frame under the engine compartment at the proportioning valve? Followed the hard lines all along the frame rails to the back axle, then out to the brakes?
Have you had the wheels and drums off yet? If not you need to pull the drums to check.

The bottom line is that it's leaking somewhere, and you should also consider replacing every component in the brake system if you want it to work perfectly and not keep failing.
But if you want to just fix what's broke without replacing every single part, you'll need to hunt down the fluid. It's going somewhere, and there are only so many places that it can hide once it's out of the reservoir.
Seems the only hiding place left you have not looked is under the drums. But double-check along the frame rail anyway, just in case you missed something.

Good luck

Paul

 

thanks for the reply
what exactly is the proportioning valve?
the only area the brake fluid spilled on was the matt underneath the engine bay,im guessing either from the master cylinder itself or from a line somewhere, but im not sure. im thinking i will fill itagain and have my dad or someone look while i pump the pedal and see where it leaks out, because it all drained out of the front reservoir in a matter of seconds, so it shouldnt be hard to spot.
my uncle said he replaced the front brakes not too long ago, but didnt touch the drums. that said, the drums from a glance seem to be alright...