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.

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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|


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Joel Adams
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

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.


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Joel Adams
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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.

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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


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Joel Adams
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

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.  

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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....

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


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


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Joel Adams
C3VR Lifetime Member #56    
My Link


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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

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)

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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.  

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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|

The speed bleeders are kewl. A little tip for using them, tho...carefully put a couple of wraps of teflon tape on the threads before installing them. This will keep them from allowing air into the system thru the threads, while they are loose for bleeding. I've seen some that come with a sealant of some kind on the threads, for the same reason.

Good luck with the bleeding...I have to say, next to standing on my head under the dash, bleeding the brakes is the worst job on one of these things...and I have a pressure bleeder!


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Joel Adams
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Thanks guys.  Last night I put together my "homemade mason jar brake bleeding reservoir" and tonight I had to put some finishing touches on it (as in some more silicone around the brass fittings).  I'm not ready to give up on that method yet, but I am seriously considering buying the speed bleeders!  I'll keep ya posted!  

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Not to me..............you do the right front before the left front. Always the furthest away until you finially get to the clostest. That's the way ebo taught me.............and I believe in ebo

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That makes sense to me and almost all non-Corvette references on the 'net seem to agree: furthest from the M/C first (although front to back shouldn't matter since they're on different circuits).  But I double checked my Haynes and found this corroborating reference online:

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Dave, the information in my shop manual (GM 1974 Sevice Manual) Says to bleed the the caliper NEAREST to the master cylinder FIRST, then the further out one. On a disc brake car while PRESSURE bleeding the book reads to hold open the proportioning valve with a tool J-23709
The manual reads "It is advisable to bleed one valve at a time to avoid allowing fluid level in resivoir to become dangerously low. The correct sequence is to bleed the valve, either front or rear system, nearest master cylinder first. This sequence expels air from lines and calipers or wheel cylinders nearest to the master cylinder first and eliminates the possibility that air in a line close to the master cylinder may enter a line farther away after it has been bled."
WOW, somehow my insticts must have been working. Two weeks ago I bench bled my new SSBC master cylinder. I then installed it on my power booster in the car. I then began bleeding the nearest caliper the (left) driver's side inboard bleeder. While doing this the outboard bleeder was spewing brake fluid. It is the Russell check valve style. The calipers are brand new SSBC 48mm 4 piston. I checked the inside seat, which looked ok. I then installed the original SSBC bleeder, which also spewed fluid. I'm using Silicone (Dot 5) fluid, which really doesn't matter. I contacted SSBC tech dept. to have the goofus tell me to tighten the bleeder more. What a joke. I finially connected with the sales dept. I spoke with a great guy. Long story-short he shot out a new caliper that I got on Wednesday. I painted it with three coats of VHT brake caliper blue paint and then one coat of clear. I expidited the drying between coats with a heat gun. Thursday I baked the whole caliper in mama's oven (she wasn't home) at 200 degrees for 20 minutes. I haven't put the caliper on yet. So this GM service manual WILL be the way that I finish the brake bleeding. Again, for some reason I started with the front driver side, which turns out right according to the manual. I hope this helps you with your project...............and GOOD LUCK to you.............You seem very meticulous, and that's the RIGHT WAY TO BE! You also really want to check on facts. I have to check the book a bit more before I just wing it. Keep us informed as to how it's going.

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Thanks for the compliment!  I'm trying to be meticulous, but I've made plenty of mistakes along the way, too.  Fortunately the big thing I've learned from all those is to not rush into things without researching them first.  Like this brake thing.  So far, my "sucking method" well....sort of sucks.  I still have a soft pedal that goes all the way to the floor but with no obvious leaks.  I'm going to bug the wife tomorrow night to sit out in the garage and do some pedal pushing for me and see if I can firm things up that way.  And I still may spring for those speed bleeders, too.  Thanks again for the help and confirming that my Haynes manual is indeed correct according to the General.  

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Thank you Dave for making me go back to the manual. I just installed my new SSBC caliper, on the left front. NOW FOR THE FUN PART. Can I borrow your wife to push the brake peddle? Just kidding I could use mine, but I have the Russell Check valve ones.  

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