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JJ62

'65 Riviera brake master cylinder o-ring versus boot.

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Hello all. 

 

 I'm going through the brakes on my '65 that has not run in years. I just went through the brakes on my '63, so I thought it should not be too difficult. You can actually order a rebuilt booster for a '65, unlike the '63. Nice.

Anyways, I tried to find an o-ring for the master cylinder so I could try the old master, see if it worked. Could not find one. Ordered a Brakebest Select 100% NEW master cylinder from O'Reillys. The picture on the website showed the o-ring, so I thought I was in business. I get the master today and it has a boot. Not too happy about that. Tried a dry run to fit master to booster and the boot is in the way. There's a round black plastic piece in the booster so there's no extra space for the boot.

 So, do I need to find an o-ring for this application? Do I trim the boot? I'm not sure what the purpose of the boot is versus the o-ring. Prevent brake fluid from entering the booster? The master cylinder rebuild kits all show a boot. They also show an o-ring or gasket, but I'm not sure if that's the right one.

 

I saw on an old post that Jim Cannon knows where to get the  O-rings. I have not been able to find that info.

Any help would be appreciated.

 

Jim

 

New master.jpg

booster.jpg

rebuilt kit 2.jpg

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The boot is used on a car WITHOUT power brakes.  It looks like the o-ring is there all the way to the lower right.  It's used to seal the master to the booster. IF it's not used you will have a big vacuum leak.  Depending on how it fits I have ALSO used silicone sealer to take up the gap. Just apply it & let it sit for 10-15 minutes before putting together.

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Okay. Thanks for the response. So, that being said, are the master cylinders the same for power/non power brakes? If so, it would be nice if the manufacturers of these masters would include both boot and o-ring in the package. I guess I will have to spend another 15 bucks for a rebuild kit just for the 79 cent o-ring...

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JJ62,

 

   What is that which looks like a flat rubber 0-ring???   When I've had a problem finding an o-ring at my shop I would just fill the back of the master with silicone. Let it sit to "Gel" 15-20 minutes & install.

   Depending they can usually be used with either.

 

Tom T.

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That fix would work in a pinch, but I don't want to do that. I'm going to return that master to the parts store. O'Reilly's description did not indicate if the master was for power or non-power brakes. I'm going to find one from another parts store that says it's for power brakes and hope for the best. The problem is that none of these masters are in stock, so you have to order them and wait a couple of days to see if it has the o-ring in it.

 At least now I know why there's 2 different pieces.

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Just about ANY master you purchase will be the same & most of them are cheap China crap.

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Update. I ordered a new master cylinder from Advance Auto, CARQUEST Wearever #MCA49201. List price $63.99. It was listed for power brakes, it showed no o-ring or boot in the picture. And it came with neither a boot or an o-ring. I am going to the store and return it, most likely. The saga continues...

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I had a shop put one on my 65 a while back that was an AC Delco from Rock Auto. He didn't report any issues, and the car stops fine. I'll try to look amd see in my shop; think I still have the old original in the new box.

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39 minutes ago, jframe said:

I had a shop put one on my 65 a while back that was an AC Delco from Rock Auto. He didn't report any issues, and the car stops fine. I'll try to look amd see in my shop; think I still have the old original in the new box.

 

 I was actually on their website a couple of days ago. On several pictures of the master cylinders they show an o-ring. I know their tech help is limited, but I'm going to call Friday and see if they come with the o-ring.

 On a couple of their pictures it shows a foam ring in place of the rubber o-ring. And I've seen the foam rings in the rebuild kits. Not sure what that foam ring is supposed to do.

master with foam ring.jpg

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 The Raybestos "Professional Grade" master cylinder PN MC36134 that I ordered from Rock Auto arrived today, 2 days ahead of schedule. The picture above that I posted is the picture shown for this part and it came with NEITHER the foam ring or the o-ring. I emailed Rock Auto over the weekend to verify that there was an o-ring in the package. No help whatsoever.

I'm not sending this one back. Now I'll spend 15 bucks for a rebuild kit and all I need is the o-ring (and hopefully the rebuild kit has the o-ring inside).

 So, the count is 3 master cylinders ordered from 3 different places and none had the proper part inside. Well, hopefully this clusterf%$k of an experience can help someone else here down the line...

 Working on old cars is frustrating enough without having to deal with crap like this.

raybestos pn.jpg

Raybestos mc.jpg

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Jim,

 

  It is my belief that the Bendix masters came with a square cut o-ring which fits into the recess of the casting. The Delco Morraine masters came with a foam gasket. I have installed many masters without either and there is no problem with function, at least on the `65 model boosters. The foam and rubber gaskets are there to seal out dirt and debris but are not absolutely necessary for basic function.

  It appears you have the Delco Morraine version...I would think a trip to your local hardware store would produce a suitable foam seal...maybe even a more suitable version that has a denser and longer lasting foam as compared to the originals which are rather flimsy.

 

Tom Mooney

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10 hours ago, Chasander said:

Booster dewy will sell you the “O” ring. 

 

Good idea. I'll contact him. Thanks.

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