Master Cyl Source

[Bill in pa]

Hi Bill in Pa. here.
As you may know I have a 1987 M35A2C
Dual circuit Master cylinder.
As I said in a different thread I bleed my brakes and the pedal will firm up then fades away.
Thinking its the master cylinder I'm going to get a new one.
Question is.
I've seen them from $70 to $170.
Is the cheep one a single circuit or is there just that much $$ difference in the suppliers?
Thanks for any help.

 

[Jeepsinker]

The cheap one is single circuit, and I've never seen a dual circuit master for as low as $170. Usually that is the high end of single circuit masters.

Usually dual circuit masters are $350 and up and difficult to find at all.

 

[frank8003]

I think this Bendix part # has been changed

NSN 2530-01-257-7643 Dual Circuit Master Cylinder

All 3 listed below are the exact same part.

Bendix part # 2232693
AM Generals part # 5934071
TACOM's part # 12357047

Another useful tidbit is the Bore Diameter is 2.742 inches min and 2.747 inches max

https://www.parttarget.com/2530-01-...ption=nsn&originalsearchtext=2530-01-257-7643

My question is were the brakes bleed in the exact sequence as shown in the Smarpie? Is there a "gooberd up" check valve in the system that can be cleaned/ replaced?
If You did not have the Smarpi it is attached here.

View attachment SMARPI TM 9-2320-209-14&P.pdf

Also here is some good comments
https://www.steelsoldiers.com/showthread.php?16675-Rebuilding-a-bendix-master-cylinder

 

[frank8003]

Bill in pa
Did you fix it? That is one heck of a truck.

 

[Bill in pa]

I have not yet.
If I give just one pump it gets hard and slows well.
I have found that Boyce Equipment has one for $500.
New in box.
I will get it replaced. im off a couple weeks so I spend less.

 

[frank8003]

There is a new one in the box for $470 to the house on the ebay
NSN 2530 01 257 7643 part 2232693 offered with 30 day returns

 

[frank8003]

Is she now drivable? NICE TRUCK.

 

[Bill in pa]

Thank You.
Truth be told I also think it turned out well.
Its always been driveable.
Just would prefer not to have to give a pump or two to stop.
Calling Napa today, from what I read
its a bendix Master Cylinder part #2232693
See if they have one or a rebuild kit.

 

[frank8003]

I did read someplace that the dual master cylinder rebuild would normally just need replacements of the o-rings. rustystud and/or many others may chime in here if that is true.

 

[Bill in pa]

Ya if I pump just once or twice.
Has a good hard stops good pedal.
Just if I continue to hold it, it bleeds down.
One quick pump and its back up
I have NO leaks.
Ive bleed the brakes per the TM
Now have all purple DOT5 silicon fluid.
Ive also read the "O" rings in it are -222 size
1.5idx1.75odx1/8 thick.

 

[gimpyrobb]

When was the last time you adjusted the brakes? Sounds like thats all that may be needed. If the pads are too far from the drum you'll need the double pump. Ive also seen 9ne of the pad retaining bolts fall off and require a double pump.

 

[Bill in pa]

Truthfully......
I've never been in there.
Just asking.
If they are out of adjustment.
Once I pump and get the shoes to the drum.
Shouldn't they stay there and NOT require a repump to keep them in contact.
What I need is some one near me with a good knowledge to learn from.