Hex plug with spring in master cylinder, what is it?

[thx997303]

There's a hex plug that goes into the master cylinder, that the rearmost line connects to. What is this plug? And how in the world do you install it? Seems like it sticks down in the piston bore on the new master cylinder, can't seem to get it installed.

 

[Garbage_Mechan]

Need to fill out your signature so we know what year truck. If it is 92 to 97 what you are describing is the proportioning valve for the rear brakes.

As far as I can remember the entire unit removes from the MC and screws into the new MC. If you have springs and things showing, did you dissassemble the little valve?

 

[thx997303]

It's a 90 f350 CCLB. It looks like I took that valve apart by mistake. Cleaned it up, took the bottom half off the old master cylinder, and the little plastic weird thing in the bottom, cleaned everything up and installed it on the new master cylinder.

I guess I was having a stupid moment.

 

[thx997303]

Grrrr. New vacuum booster and master cylinder. Truck stops much better, but pedal still feels soft.......

 

[thx997303]

Well, that proportioning valve is now leaking horribly, causing a soft pedal.

So, what do I do here?

 

[thx997303]

Well, found the part number. F8UZ-2C161-AA

$45 part it seems, have to get it from ford.