Mercury Cougar Owners banner
1 - 20 of 25 Posts

·
Contributing Member
Joined
·
1,909 Posts
Discussion Starter · #1 · (Edited)
Just pulled this Midland banded brake booster out of a early 68 XR-7 and next to it, what looks like a 70s vintage Bendix master cylinder with the stop screw.
The 68 XR-7 had just under a 100,000 mi. She sat in a back yard up in New York State for 17 years and in a garage in Florida for the last 21 years.
It's going to be fun rebuilding this one. It still has the Oetiker hose clamp on it so I'm hoping it has never been rebuilt.
I plan on documenting this one and posting thru the refinishing and complete rebuild.

The master cylinder next to the Bendix appears to be a Delco-Moraine with the inside stop screw. I pulled that one out of a 67 Cougar.
The Ram Man.http://www.theramman.com/will know for sure.

You can read about the stop screw here http://www.deadnutson.com/catalog/item/4065497/4973334.htm


Has anyone here ever tried to rebuild a Midland ? They're really not that difficult. The last one I did had about a half cup of fine powdered rust inside.
The Master cylinders will be more of a challenge.






Here's a better pic of the stop screws.











On the Bendix MC with the outside stop screw, you can't rebuild them without removing the stop screw first! These are usually the most difficult because they more than likely rusted in and have to be drilled out.

There is a way to get them out without damage and I'll cover that procedure when the time comes. If you have one of these Master cylinders DON"T turn them in as a CORE!

They are worth $$$. This one happens to have the course thread screw.

 

·
Contributing Member
Joined
·
1,909 Posts
Discussion Starter · #3 ·
Well I disassembled the bendix. The 1 inch bore still looks pretty good, I was afraid I would have to sleeve it. Next finish de-rusting, hone the bore, paint, install a new valve, re-use the brass fittings, install new primary and secondary pistons and bench test for cylinder bore leaks.

I'm waiting on a power supply before I tackle the midland because I want to nickel plate some of the internal components when I disassemble the unit.


 

·
Contributing Member
Joined
·
1,909 Posts
Discussion Starter · #5 · (Edited)
Just finished with the Bendix, bench bled and no leaks!! I got tired of using the rubber and plastic bench bleeding kits. Screw in the fittings too tight it leaks, screw in too loose they leak so I made a kit out of some extra brake line and fittings.






I used this double flare tool that I bought to do on the car flares. It really makes great double flares better that some more expensive kits. It only does one size,3/16.

There are several vendors selling these and they slap their own name on them so they are easy enough to find.

What I like about this tool is there is no guess work. Just screw in the stop screw, insert the brake line till it rests against the stop, (it even has a sight hole so you can see it against the stop) tighten the brake line in the block with the two bolts, remove the stop screw, then screw in the op1 die till it bottoms out, unscrew and screw in the other side till it bottoms out and you end up with a perfect double flare that doesn't leak.




There is one important procedure that I would recommend when bench bleeding. USE A WOODEN DOWEL to depress the piston. Don't use a screwdriver!

A long wooden dowel with the little less outside diameter as the inside diameter of the piston will give you better leverage, more control and won't scratch or gouge the piston.

When using a screwdriver you tend to push the piston to the side thus putting unnecessary pressure on the seals against the bore.
Don't forget the seals ride on the bore not the pistons!





 

·
Contributing Member
Joined
·
1,909 Posts
Discussion Starter · #7 · (Edited)
Well I'm getting ready to crack this egg open. Tried to use supermotors to post more pictures but I found out that they are NOT A SECURE SITE! So watch it!

Anyway, since the band screw is corroded I want to get the corrosion off first before I try to remove it.








I've got it wired up to take off the corrosion with electricity by using a battery charger, water and super washing soda as an electrolyte. I'll let it work for a few hours and post back.








well after looking at the bolt a little closer I could see that it had been crimped so it had to be cut off.

After removing the band the rear casing could be removed.




The front case is held by the flange of the bellows.







Rust inside the case is the reason why these Midland boosters can fail after a few years or sooner.

In this picture the rear diaphragm failed. Look at the rust that has built up under the band and the ribs of the front diaphragm too.

These units are atmospheric so when the brake is released air is drawn back in the case. Moisture in the air and untreated metal = rust.



As the rebuild continues all internal parts will be treated with por15.
 

·
Contributing Member
Joined
·
1,909 Posts
Discussion Starter · #11 ·

·
Contributing Member
Joined
·
1,909 Posts
Discussion Starter · #13 · (Edited)
Now before some of you go and order a repair kit there is something you should know.

In order to remove the front and rear diaphragm from the power valve (control hub) you will need a special tool. Harmon classic brakes sells this specific tool but it's not cheap. PN 62-314

Here is a picture of the tool and the power valve. This tool mounted in a vise gives you the leverage to turn the front and rear diaphragm off the locking ribs on the power valve.



If you look closer at the power valve (control hub) you will see different slots on the sides as well. There were other tools that were used to do the same task resembling a spanner wrench.

When you buy a complete rebuild kit you should receive a copy of the complete break down front to back of the of the midland banded power booster with each individual part number.
The only one in you will ever find anywhere! Believe me I have researched this for a long time. I will not post it!

You will also receive a blurry copy of a service manual's instructions on how to take it down for rebuild.

Ford never published one as far as I could find but I could be wrong. MOPAR DID! They used the same booster with a slightly different case.

It is in the 1967 Dodge Dart + Coronet and Charger service manual on pages 5-22 thru 5-28.

I'll show you where you can download this service manual for free and you can read all about it with pictures.
MyMopar - Mopar Forums & Information - Service Manu


and you can see the tool that they used.

 

·
Contributing Member
Joined
·
1,909 Posts
Discussion Starter · #15 ·
Since I removed the outer front and rear case I went ahead and de-rusted and painted the inside and outside with POR-15.



I will also deburr the leading edges (both sides) of the rear diaphragm assy. The rear diaphragm is sandwiched between two discs spot welded together. The edges that are curled away from the rubber are razor sharp! That will also be treated with POR-15.


 

·
Contributing Member
Joined
·
1,909 Posts
Discussion Starter · #17 · (Edited)
Now it's time to remove the bellows. Depending on whether or not you want to save the band clamp there is one method that can be used, the other two will destroy the clamp.

I always use this method using an old pair of lock ring pliers and expanding the crimp just enough (not too much) to loosen and remove. This way it could be used again if need be.




The second method would be just to cut it off.




The third method would be to pry the overlap up and it will pop right off. This is the better of the two because there is less chance if damage to the rubber.





Now that the bellows has been removed you can see how the rust destroyed reaction lever assembly. I put a new one in the picture to show the difference. Some of the metal pieces either rusted away or they just fell off. I didn't find any loose pieces in the case.

Also in the picture I added a cleaned up push rod assembly. The little plastic clip holds this assembly in the the power valve. you can see the one I just took out is rust welded on the rod.

That will come off easily when I use the electrolysis method.




As for the bellows, It still looks good but I won't use it in the rebuild. I do have to reuse the two support rings. They will also have to be cleaned up and nickel plated or painted with POR15.

I added a cleaned up support ring in the picture. The support rings start out as round flat discs and are rolled up so the area that makes contact with the rubber has a radius. When the rings get rusty they can cut into the bellows







In this picture the reaction lever is removed and the face of the power valve is exposed. Look at all the rust! Now you can see the two slots that are used for the Special Tool to remove the rear and then the front diaphragms.





Next will be the removal of the rear and then the front diaphragm. If rust builds up under the locking flanges it can be very difficult to remove. There is also a risk of breaking the plastic ribs on the valve. Both of the diaphragm plates don't look too bad in the areas that lock onto the power valve so I will use the BEST penetrating oil on the market. (DEEP CREEP)




Sprayed on the DEEP CREEP all around the locking ribs and let is soak in for a few hours. The DEEP CREEP will soften any rust.


Well the diaphragms are off with less effort thanks to the application of the DEEP CREEP!




In this picture you can see rust that was on the locking flange of the front diaphragm.




Next, refinish all rusty parts and rebuild the control valve.
 

·
Contributing Member
Joined
·
1,909 Posts
Discussion Starter · #18 ·
As you can see I left the brake rod on the assembly attached for now. I know from experience something is different about this one and I'll show you later how I remove it and why.



When disassembling the power valve there are usually three things that hold it together, the snap ring in the front, the spring retainer in the rear and RUST throughout.





After spraying it down with DEEP CREEP and letting it work for a few hours I removed the snap ring in the front and carefully worked off the front of the control hub.




Moving to the rear I use an old pair of fixed snap ring pliers for leverage to compress the spring to remove the spring retainer.




After the spring retainer is removed the hub assembly can then be slid aft ( to the rear) which exposes an area of the plunger between the flange on plunger and the spring seat and rubber valve.



Now back to the brake rod. The way I always remove the brake rod from the plunger is to mount a adjustable (spanner) wrench in a vise and open it to the diameter of the plunger. Slide the plunger in the opening of the wrench and rest it against the flange of the plunger. I then attach a slide hammer to the eye of the brake rod and give it a easy tap.

The reason why I do this is because the force is is limited to the flange on the steel plunger and not any of the plastic assembly of the hub. Also keep in mind that not all re-builders assemble the same way.

Case in point, when I removed the brake plunger on this one, the builder used TWO retainers instead of one which made it excessively difficult to remove by hand. I have had this happen before and that is one of the reasons I always remove it this way.




Now that I've finished complete disassembly of the power valve I can begin cleaning and removing the rust and refinishing the plunger which is the only part of the internals to be reused.
 

·
Contributing Member
Joined
·
1,909 Posts
Discussion Starter · #19 · (Edited)
When I removed the plunger I compared to another one I had. The one I'll use in this build is the one with the three ribs but first I'll want to clean it like the one below before I coat it with POR15.




Here are the parts that make up the plunger assembly.



I cleaned and coated the plunger with 3 thin coats of POR15 I'll start the build with installing the O ring with a coat of red rubber grease.






The rubber valve is greased then slipped on, (concave side facing the spring) then the spring seat (protruding rib facing the spring), then the spring and to lock it on the plunger the spring retainer.

Don't forget to slip on the fiber washer on the front of the plunger before the assembly is inserted into the control hub.







There are two alignment studs that should align the holes in the rubber valve.

There are also two O rings. The big thick one on the bottom and a small one on top of the control hub shaft. Then the Tail stock can be slipped on. That's all there is to the control hub assembly.



After the tail stock is slipped on that's when I slide in the valve operating rod. (brake plunger) It just makes it easier for me when I'm installing the front and rear diaphragms.



Next, Installing the front and rear diaphragms without using any special tools.
 

·
Contributing Member
Joined
·
1,909 Posts
Discussion Starter · #20 ·
The front and rear diaphragm are now installed. I used this and a vise.







With a rubber strap wrapped around the front of the control hub mounted in a vise, I was able to use both hands to turn on the front than the rear diaphragms on.



All of the parts were painted with POR15 so this booster shouldn't have any rust issues inside or out



I assembled the bellows and I'm almost ready to finish this one.




Next final assembly.
 
1 - 20 of 25 Posts
Top