I decided my reaction disk had slipped. I have the master cyl off , booster still on the car. I can not locate the disk. Any suggestions on fishing it out would be appreciated before I pull the booster. Thanks JB

You can cut a new one from thick rubber and glue it on the rod.

Take a look at rubber door mats and door stoppers/bumpers if there is no supplier of rubber stock sheeting in your area.

I agree with Blue....also you can neck down a small section of hose to your vacuum cleaner with duct tape....fish it around in the hole and it will stick to the end of the hose! :bulb::bulb::bulb::bulb::bulb:

Thanks Blue and Deseazd, Both good ideas I had not considered. If the vacuum cleaned does not work, how thick do you think the rubber should be? I picture it about 1/2 to 3/4 inch thick. What do you guys think?? Also I wonder what role the thing plays as far as how the booster works.

Thanks again for the replies, JB

It's in there......get it if you can (no way it escaped). The booster is miserable without that little disc.....feels like you have to put both feet on the brake pedal to stop the car. Super glue it to the plunger.

The reaction disk is only about 1/4" thick, maybe 3/8.

Pics here : https://www.google.ca/search?q=reaction+disk+site:www.classiczcars.com&espv=210&es_sm=122&source=lnms&tbm=isch&sa=X&ei=Gs0XU9q-OuzH0gGEtICgDg&ved=0CAkQ_AUoAQ&biw=1137&bih=570&dpr=0.9

Thanks again for the info. I will try again to fish it out and if not I plan to pull the booster. I don't think it would hurt to be left in there but I want it out. I still don't understand what role it plays. Anyway thanks for the help. I'll let you know the outcome. JB

When you drive with and without, you will quickly understand the role it plays. without it the brakes seem to lose all modulation. very on/off.

http://www.classiczcars.com/forums/wheels-tires-brakes-s30/34288-mystery-71-240z-brake-issue.html

Mine came out when I removed the booster and shook it vigorously. I think I may have reached in and dislodged it with a finger first.

http://www.classiczcars.com/forums/wheels-tires-brakes-s30/34288-mystery-71-240z-brake-issue.html

That is what I have had going on. About the top 2/3 of the pedal travel nothing happens/ I have worn out the adjusters on the rear brakes and put brake fluid companies on overtime trying to bleed the air out.

I hope to get the disk out without removing the booster but will do that if I have to. I guess the disk has been missing since day one (for me) since I replaced every thing but the master cyl and could never get a full pedal. Then I replaced the master cyl and still had the same problem. Thanks everybody for all the good advise. JB