| Re: [GMCnet] vacuum booster MC seal (Tom Whitton) [message #270857] |
Fri, 30 January 2015 22:48  |
Tom Whitton
Messages: 235
Registered: February 2004
Location: Paducah, KY
Karma:
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Senior Member |
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Rob,
Thanks for the information. I don't know if I have that seal (Key 9 - Seal / PN 5460935) or not. I'll have to take a look over the weekend. If not, do you think installing the seal will decrease the cycling of the vacuum pump or are Dave's components necessary for the decrease? I haven't looked yet to see if the seal is available these days. If memory serves, Emery wrote that the seal that Dave furnished reduced cycling of his vacuum pump. Emery did not mention Dave's manifold, etc.
Tom Whitton
26 foot updated GMC
Paducah, KY
Message: 15
Date: Sat, 31 Jan 2015 13:36:59 +1100
From: "Robert Mueller"
To:
Subject: Re: [GMCnet] vacuum booster MC seal
Message-ID:
Content-Type: text/plain; charset="us-ascii"
Tom,
Dave makes a "plastic" sleeve that goes over the "tail" of the master cylinder to center it in the booster. They come with
sensitized boosters purchased from him.
I spoke to him just now and he advised that has made some for GMC owners but there are a number of variables concerning the booster
and master cylinder installed that he has to know before he can make one. Basically he needs to know the ID of the booster and the
OD of the master cylinder because they are not all the same.
He noted that at a later date he would be willing to make them available; however, at the moment making these is a low priority due
to his health issues.
My personal request to everybody out there, PLEASE don't start calling him for this item!
Even if the booster was vacuum tight your vacuum pump would still cycle because the pressure switch that senses pressure is between
the booster check valve and the vacuum pump. There are check valves in the vacuum pump that leak allowing air into that line and
when the pressure goes above the setting the pump starts. Dave also makes a manifold that plugs into the booster and the check valve
plugs into it, The pressure switch goes into that manifold and senses the pressure in the booster upstream of the check valve.
See Parts Book 78Z / Section 4 - Brakes / Page 4-8 & / Key 9 - Seal / PN 5460935. Note how it is cup shaped to fit over the M/C
Tail.
Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
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