So I took my master cylinder back off and did a bunch of measuring.

Under vacuum, my brake booster pushrod extends an additional .150".

I measured the inside of my master cylinder, from flange to flange etc and did some math.

I need my booster pushrod to extend only ~1/4" from the inside booster flange under zero vacuum to have clearance on the master cylinder end.

I can get the pushrod to lengthen....but it won't retract any. It appears that I'm still 1/4" away from having the booster pushrod in far enough to not cause me master cylinder problems.

After a certain point, which still isn't far enough, the internal flange of the booster just starts backing itself into the booster.

It looks like this:



Am I screwed? Is there not a way to fix this? Does this mean that the brake booster rod is adjusted back as far as it can possibly go?
I need to be able to get this done using this brake booster. It's a 4+ hour job to remove it

For what it's worth, it's a '91 EX master cylinder with a '91 LX brake booster. I've had the setup before in a previous car and had no problems whatsoever.

I really need some help/ideas here! I've been having problems with my brakes sticking/dragging and I think I've finally narrowed it down to this.

 

do you have another similar booster outside of the car to experiment with?

that would be your best bet.

if you REALLY are hurting for this, i have one out of an 89 si that should be the same, i can look at it closely, cut it, whatever and take measurements tomorrow if need be. pm me if you need it. just do it soon, because i might be leaving for a month on saturday.


also, i know you don't wanna hear this, but if it won't adjust anymore, try taking the booster out (i know, 4 hours of labor) and putting washer shims between it and the firewall.

 

I actually have a few spare boosters that I've tried experimenting with.

All of them do the exact same thing....they won't adjust back as far as they need to go. All of my spares are Honda OEM boosters.

Which makes no sense to me considering the master cylinder is also a Honda/Nissin unit.

I mean how can it not adjust far enough back to allow proper operation between the master cylinder and the booster? If I can't come up with a solution tomorrow (my only day off), I'm going to take a cut-off wheel to the end of the booster pushrod and then round it back out with a stone wheel.

Seems to be the only logical and time-friendly solution.

Thanks for the reply bro. There seems to be little help here on Honda-Tech when I actually need help with some tech!