mystery disappearing brake fluid

[ramos291]

Found the vacuum leak. missing O ring on the new M/C on the end where it seals with the booster. My mistake for not seeing that the new M/C didn't come with one on it.

[Dan Leavens]

Randy great to see you found the issue, brakes are a good thing

[jopizz]

Found the vacuum leak. missing O ring on the new M/C on the end where it seals with the booster. My mistake for not seeing that the new M/C didn't come with one on it.

That's a lot cheaper fix than a new booster.

[ramos291]

Indeed it is however I am sure a booster replacement is in the future. At this point though I would like to replace that seal and not use the old one. Finding a new vacuum seal is now a difficult task. It would seem that the supplying web site as well as the manufacture do not know what a vacuum seal is. Am I telling them the wrong name for this seal?

[jopizz]

There's a groove on the end of the master cylinder where it looks like an o ring should be but I've never actually seen one have it. Your booster should not be leaking vacuum where you need an o ring on the master cylinder to seal it. If your booster is working correctly you can leave the master cylinder off and you won't lose vacuum. I'm afraid your booster is still shot.

John

[ramos291]

from what I have read, 60 and 61 bendix brakes used a squared O ring to make a seal at this spot. Good news too, I found the part #
B8S-2493-A. My brake booster is not a clamp around type but rather screw type. Meaning screws are used to keep the two halves of the booster together. Not sure of other differences. If you would like, check out the link below. Its a bit of interesting information, I thought.

https://www.vintagethunderbirdclub.net/phpBB3/viewtopic.php?t=8389

[jopizz]

As mentioned in the thread the seal really doesn't do much. It's more to keep moisture out of the booster than it is to keep vacuum from leaking out. There are various seals and valves inside the booster that hold the vacuum and keep it from reaching the outer case. If you have a shop manual it will have an exploded view of all the parts. It sounds like you have a Bendix booster, not a Midland booster that used the screw clamp.

John

[ramos291]

So an update to this master cylinder and brake booster ordeal, I shipped both the master and the booster to Power Brake Booster INC. Dewey to do a rebuild. FINGERS CROSSED here.
Thanks again for all your input guys. Thank you

[ramos291]

last update. Newly rebuilt brake booster and new dual M/C with proportioning valve installed in car. Brakes plead and all seems fine. Test drive went great.

[jopizz]

Glad to hear that it worked out. I think we all suspected that it was a booster issue from the start. You sent it to the right place to be rebuilt.

John

[ramos291]

Glad to hear that it worked out. I think we all suspected that it was a booster issue from the start. You sent it to the right place to be rebuilt.

John

Thanks again for your help. Now on to the switch from gen to alt. Finding one that fits my finance and car.