I have just replaced the power brake booster on my 84 F150, it said on the label of the new one that some adjustment may be needed on the pushrod....the hissing is gone from the old booster, but the brake pedal is mighty soft........how is the pushrod adjusted and when is enough???
I f you unbolt the master cylinder and look at the end of the push rod you will see a nut. hold the rod turn the nut in or out. if the pedel is soft will have to make it longer.the spec is from the flat surface of the booster insde the two studs that hold the master cyl. on to the end of the rod. the spec is .980 to.995. I adjusted mine just under a inch and when I put the master cyl on I made sure that it went flat against the booster with no pressure. If you have it adj. out to far the brakes will drag. the rod would be hitting the spool in the master cyl. and applying the brakes. Hope this helps.