Ok, I will try again with these. I know the later MC will fit the 87 up booster and the 87 up booster will fit the same pattern on the firewall as the 86 booster. Here are a couple of pictures of my setup using a 1990 booster and a 1993 MC with the cruise cancel and line for my hydraulic actuated trailer brake controller.

 

Okay, replace stroke with displacement then.

 

I am slowly making process here, it was mentioned in an earlier post here that possibly I should have plumbed the larger reservoir of the master cylinder into the rear brakes since there are 4 wheel cylinders there.

I acknowledged this as a possibility I believe and asked for confirmation that this would make a difference but do not remember reading any further comments so I will bring this back to the table.

I am not clear I guess on why there are two different sized reservoirs, ok one is for disk and the other for drum......Ok if I consider this than knowing disk brakes require more fluid volume than wouldnt they be plumbed always into the rear reservoir?

How does this rear larger reservoir deliver more volume, I do not get it, I understand there is more fluid within the reservoir but how does that affect the volume. Is there a larger outlet port for the larger reservoir? I do not think so after looking at the master cylinder.

Anyway if this the case that the larger reservoir will deliver more fluid than I have it bass ackwards as I have the larger reservoir delivering fluid to the two smaller front wheel cylinders.

Can someone explain all of this too me? Thanks

 

This is what I do know;
The disc brakes have more fluid in them, so they will require more fluid from the reservoir as the pads wear.

Why are they backwards? I don't know, but you are correct, the disc brakes take the larger reservoir. When people convert their trucks to rear disc's guess what? They usually use the original master cylinder and use the little reservoir for the new rear disc's.

What do we know so far? You had brakes, not great brakes but you did have brakes, and after messing with them, you lost it. I have had two different things cause this when working on vehicles;
1. I accidentally let one of the reservoirs run out of fluid when bleeding or;

2. I had a small leak somewhere. Like someone else previously mentioned, a very small wet area at one of the fittings will not leak much fluid, but will let air in and ruin the whole thing.

I am also suspicious of your old timey wheel cylinders. When I was retro fitting a old mustang, I did some research on the residual valve debate. Most all older master cylinders had a residual valve at the master cylinder when using drum brakes. I found out from reading that the main purpose for these valves was to keep the seal cups in the wheel cylinders out against the cylinder wall. When you let off the brake, they had a tendency to "suck in" and let air into the system. Then they said sometime over the years, all the wheel cylinders started using springs behind the cups, and this pretty much eliminated needing residual valves, and a lot of the newer masters do not come with them.

I am wondering if this newer master does not have a residual valve in it for the rear brakes, and your wheel cylinders may be old and do not have the springs behind the cups? This is another thing we know; The problem is at the rear correct? Because you keep pinching the line off to the rear and you suddenly have brakes. That means the problem is in the rear end somewhere and is caused by something back there.

 

The only master cylinders with different dispalcement volumes are the step bore GMs. Even my 1993 master cylinder has a residual pressure check valve.

 

Do you have the specs for your master that shows the valve? Or did you pull the seat out and find it? It only has it on the small reservoir for the rear correct? Not in the front for the discs.

This would be one reason not to put the rear wheel cylinders on the larger reservoir.

 

Have you ever looked at a 1987-96/7 master cylinder? The valve housing protuding from the rear port is the residual check valve. On the 86 master cylinder it is located in the forward (rear system) outlet port. When I get home I will scan the 1991 chassis manual brake section for your edification. BTW, my 1985 Chrysler LeBaron had two residual pressure valves, one for each rear wheel since it has a dual diagonal system.

Our 1953 Chrysler Imperial had spring expanders in it's 6 wheel cylinders, two single ended ones in each front wheel and one double ended one in each rear wheel. My 1966 Shelby had a residual check valve on the rear brake pressure reducing valve.

 

I have residual valves on both front and rear lines coming off the master cylinder, they are the small red things within a picture that I have posted in the past on this thread. They are made by Wildwood and I ordered them thru Summit. 10 lb residual pressure check valves.

From what I have read it makes no difference if you have multiple valves within the system, there is no benefit or harm in other words.

I do not know where the problem is at this point, I have not had good brakes at any wheel. Yes I can pinch off the rear line and then I have a stiff pedal but still no decent front brake pressure.

 

Sorry to sound like I doubted you. I would like to be educated a little more on this though.

 

No problem, I will scan the 1991 chassis manual sections when I get home and probably put them on my website downloads so others can see it.

Other than his now verified MC problem, what I was telling the OP quite a ways back, was the issue as I saw it was he had increased the volume of the rear system by 16% per cylinder and decreased the volume displaced by the MC by 30%. From there it almost becomes a no brainer if you have ever messed with hydraulics at all.

 

Your front problem could be the shoes aren't fully contacting the drums. Possibly an anchor pin adjustment if there is one might help. The other issue might be that you are bottoming the piston you are using for the front brakes (a dual circuit MC will do this, each piston is 1/2 of the total travel). The piston only goes until it hits the other one or the end of the MC bore.

 

All good points and please bear with me as well since I am also learning, I plan to re-adjust the front brakes this A.M the official by the book way with feeler gauges and all believe it or not. This is how the service manual specifies this needs to be done.

As far as ..........The other issue might be that you are bottoming the piston you are using for the front brakes (a dual circuit MC will do this, each piston is 1/2 of the total travel). The piston only goes until it hits the other one or the end of the MC bore.........This master cylinder has a 2 inch stroke, the original 52 had a 1 7/16 stroke which was a single cylinder round canister looking deal so unless I am looking at this all wrong I should have more peddle room so I cannot see how I could be or should be bottoming out before the front brakes lock up.

Correct me if you see things different than how I am looking at them.

I am also looking into the master cylinders variety that you mentioned, you have told me that the later master cylinders will fit the power brake booster, I hope that you have not specified this already because I hate to ask someone that has already given me information to repeat it because it shows a lack of momentum to read the help given in the first place but I will ask anyway and then edit the post if I see that you have answered the question already.

How late of a master cylinder ( approx if thats all you can give ) will fit onto the mid eighties power brake booster?

Second question.....I know ZERO about these later master cylinders with plastic separate fill tanks. What are some of the differences I need to be aware of, I dont want to buy something that will not function as I need it too and I notice on the pictures you gave that their are all sorts of doodads on those master cylinders.

Electronic Doodads and looks like addit. lines as well.

I am thinking that if I can find one of these LATER master cylinders with the same 1.5 inch bore than I will be one step closer to solving any problem that I may be having.

Thanks for your time!!

 

Hope this helps. If you aren't too far away I can send you the old 90 MC for fit up.

 

I may take you up on this......Bill, I have this discussion going on another Ford forum, not FTE. I know you are old enough to understand that it took more than one man to build Rome and all experiences are helpful so I do not think you will be insulted by me telling you that.

Anyway it has been suggested that even though I HAVE stopped the truck years ago with an even smaller master cylinder and booster that I simply do not have enough volume right now with this master.

Without getting into my opinion on that at this point will you and anyone else please give me your opinion on this...I found this on the net doing a quick google search and it is affordable.


ECI Brake Pressure Multiplier

Recipient of the 2004 NSRA Best New Product, and Best New Safety products Awards

The ECI brake pressure multiplier (BPM) utilizes a unique step piston configuration to increase brake system pressures 50-60% where it’s needed most- at higher pedal forces. The BPM uses the excess fluid capacity available in the master cylinder bore to provide increased line pressure for the low volume requirements of a small piston caliper brake system, such as Ford Explorer, Corvette and GM rear disc brake calipers, and is ideal for use with rear drum brake systems.
Due to it’s step piston multiplication system, the BPM continues to provide 150% to 160% of inlet pressure as pedal effort increases, unlike a vacuum booster’s assist, which remains constant after maximum
boost is reached with line pressure only increasing linearly with increased pedal force.
Low pressure operation and system filling remain unchanged, with pressure multiplication occurring only at the higher pressure levels required for optimum system performance. Each BPM is tailored to your exact system requirements during assembly to provide the
maximum increase in pressure and brake performance. A slight increase in pedal travel is required for operation.
The BPM is installed in the brake line and can be used with or without a vacuum booster. Chassis mounting is required..
EC-1500...................................$ 159.95



Maybe I am so far off in left field that it isnt even funny, you tell me

 

I am still un-clear ( good explanation above BTW ) of OK so I am lacking 7/16 throw but the original used the 1 7/16 for all four wheels as well, please help me to understand better. Thanks