M/C pushrod free play

[PatO]

Hi, I've got a question today.  I recently purchased a refurbished Midland Ross vacuum booster from Booster Dewey for use in my 72 Challenger.  I was looking to try and set the endplay where the pushrod meets the master cylinder piston.  What I can't get straight in my head is that I have over 1/4" of movement  (slop ?) in the push rod in the booster unit.  I can move my brake pedal forward an back and observe the movement of the push rod through the booster. If I position the rod all the way back into the booster, the adjusting nob on the end  of the push rod needs to be adjusted almost its entire range of movement. Something doesn't seem right. 

Does the booster need to have vacuum applied in order to adjust the push rod correctly?   Or am I missing something?   Please feel free to set me straight. I'm thinking it's something simple, just not getting is straight in my head.

Thanx!

[Cuda Cody]

Do you have the right parts?  I do not recall ever having and slop in mine when he rebuilds them. 

[PatO]

Hi Cody,

Just holding the unit in my hand I can move the push rod front to back to front again without any effort. This is a bit over 1/4" travel before it meets any resistance in the forward direction, as in putting on the brakes.

I have a Bendix unit also, new from Roseville Moparts, that takes a bit of hand pressure to move the push rod forward - and you can hear the air moving.

I should probably call Booster Dewey to see what they think. 

[Burdar]

Call Dewey and see what he says.  I think mine was that way too though.  Maybe just the way the Midland Ross boosters are.  It shouldn't matter.  Just make sure the pushrod is all the way "back" when you adjust it.

[1 Wild R/T]

Are you are talking about moving the pushrod on the back that attaches to the pedal linkage or the pushrod in the front that contacts the cup in the master cylinder? 

[Burdar]

IIRC mine had some in and out slop on the master cylinder side.  With the master bolted up, it will push the rod back...removing the slop.  I might be totally remembering it incorrectly too though.

[1 Wild R/T]

On the M/C side often the pushrod can be moved or on some even removed......

On the back side the pushrod actuates a valve plus it will transfer pedal pressure through the booster when theres no assist..... A redundant safety design...  But actuating that valve means you'll have a dead area which I suspect is what the OP is observing....

[PatO]

Hi ! - Thanx for the reply's.  Would have gotten back sooner but I'm busy getting my engine bay, engine/transmission ready for a Saturday morning install.      

I did get with Booster Dewey, and you are right Burdar.  There is a certain amount of free play in the booster when there is no vacuum applied.

Now, since I messed with it first and asked questions later, I need to get back and readjust the screw/knob on the master cylinder side of the push rod back to what it was.

Thanx Again,  always great to get your opinions.