The AIM for my car shows a gasket and retaining ring in between the master cylinder and the booster.  Should my new (reman) master have come with those?  I took the old one off months ago and don't remember what I did with them, or if they were even there.  Anyone know where I can get those?  A related question: can I buy the pushrod seal that is tucked inside the booster? I presume that is important in regards to holding vacuum and the old one looks OK, but not great.  Thanks, guys.

There IS a seal between the master and booster...not sure about a retaining ring. I traced a vacuum leak on my '74 to this seal several years ago. I wound up using/modifying one of my old headlight actuator seals for mine, and I don't know if these seals are available anywhere. There was another discussion about this same issue a while back, and I think I suggested contacting someone who actually rebuilds the boosters to see if the seals were available.

|UPDATED|5/25/2012 9:21:23 AM (AZT)|/UPDATED|

I'll look and see...I have the '73 and '74 AIM. I'll check the Service Manual, too, just in case there may be something in there...

I don't really remember what I did to get the headlight seal in there, but...best I can recall, the purpose is to seal the master against the booster, as a redundant seal, if the pushrod seal happens to leak. I had had a nagging vacuum leak in mine for years that I just couldn't find, and I finally traced it to the master/booster. Of course, if the pushrod seal weren't leaking to start with, it wouldn't be an issue. All you need is some sort of seal that fits the diameter of the hole in the booster, and is thick enough to seal against the master, without being too thick to allow it to bolt up tight/flat.

Thanks, Joel.  I think I may have came up with a solution.  I had a coffee can full of misc plumbing washers and O-rings.  I used one of those reddish ones with flat sides and put it in the machined groove on the M/C.  Then, since it still wasn't really snug in the booster, I butted up a black o-ring type against that washer and it's an obvious snug fit now.  Since it's only a backup for the pushrod seal it should be fine.

Upon further investigation, I have determined that the "gasket" in the AIM is really called an air filter. It is not rubber, but more of a felt type material...it's purpose is to keep dirt/crud out of the space between the master and booster. It does actually fit into the groove on the end of the master, where you say you put your o-ring. 
The Service manual does NOT cover rebuild/service of the master cyl, but it does cover rebuild of the booster. It also shows a very nice cut-a-way of the booster/master, which plainly shows the "air filter".
My memory of original cars is that the felt-like "seal" is usually crumbles by the time the master is removed for service, and never replaced. The "retainer" noted in the AIM is, if I remember correctly, just a piece of cardboard-like material, to keep the felt from being bent out of position on installation of the master. So, basically, the "gasket/seal" is NOT meant to be a backup seal for the booster...just a dam of sorts to keep foreign material out of the space. And now ya know!

Yes..you DO need to bench-bleed the master...regular bleeding of the brake system will NOT get the air out of the master...and ya gotta get that out before you can bleed the rest of the system. Most masters come with hoses and attachment to bench bleed them...if not, you can get a bench-bleed hose/fitting kit at any parts house for very little cash...prolly $5 or so. The "kits" usually have several different sized hoses and plastic fittings.
hth

Very interesting, Joel!  Thanks for researching it for me.  I think I'll leave my washer/O-ring set-up and call it good.  I might have to invest in a real service manual - my Haynes manual in conjunction with the AIM covers most things, but not all.  

Here's the page from the '73 AIM that shows the "gasket" in question. If you'll notice, the gasket is too large to fit up inside of the booster, and sit flat against the seal that is already there. That's what my "modified" headlight seal does...it sits flat against the master end, and the seal of the booster. At least it "fixed" my vacuum leak. Of course now...vacuum is prolly sucking fluid into the booster...

I guess it might help if I actually put the LINK to the page in the post....

http://www.c3vr.com/member_uploads/4401_4500/4427/mastercyl.jpg


|UPDATED|5/26/2012 7:51:56 PM (AZT)|/UPDATED|

Thanks, Joel.  My AIM looks pretty similar.  I think the mystery has been solved.  I'll probably hook up my vacuum pump to the booster and make sure it holds - if it does it seems like I'll be good.  (At least until that pushrod seal goes out -- if it does I'll know the culprit right away)

Took me two tries to get a setup that would hold vacuum.  I think my pushrod seal is worn out - first time I relied only on that and would not hold any vacuum.  Then I tried the headlight actuator seal over the pushrod as well as my o-ring setup around the M/C and held just fine.  

Dave, Bleeding brakes is always aggrivating but Russell speed bleeders make the job almost painless. Only one person required and Ive even bled two calipers at the same time. No pumping up and holding just pump the brake pedal slowly and firmly. 

 

|UPDATED|5/31/2012 5:58:36 PM (AZT)|/UPDATED|