Seal between P30 MC and booster.

RF_Burns

RF_Burns

Super Moderator
Staff member
Sep 7, 2008
5,131
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113
Ontario Canada
So before bleeding the brakes after installing the new caliper, I wanted to check the clearance on the MC push-pin. I loosened the MC move it out of
the way. I can see there is water leaking into the nose area between the MC and the booster (rust!). I have a P30 MC with the support bracket between
the MC and the booster. There does not appear to be anything to seal water out of this area. Especially with that bracket in between.
Am I missing a seal here? There is a rubber piece in the booster around the push-pin, but it appears to be too far in to mate to the M/C.
--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
Hubler 1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
David Lenzi has addressed this problem (and vacuum leakage) and has had seminars on it at GMCMI conventions. He has machined parts to give the proper seal. You might want to contact David about your problem.

Emery Stora
77 Kingsley
Frederick, CO

>
> So before bleeding the brakes after installing the new caliper, I wanted to check the clearance on the MC push-pin. I loosened the MC move it out of
> the way. I can see there is water leaking into the nose area between the MC and the booster (rust!). I have a P30 MC with the support bracket between
> the MC and the booster. There does not appear to be anything to seal water out of this area. Especially with that bracket in between.
> Am I missing a seal here? There is a rubber piece in the booster around the push-pin, but it appears to be too far in to mate to the M/C.
> --
> Bruce Hislop
> ON Canada
> 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
> Hubler 1 ton front end
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
> My Staff says I never listen to them, or something like that
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
The original rubber gasket that had a sleeve that fit over the nose of the master cylinder is no longer made but I had gotten a part that David machined from nylon (or other plastic) that filled the space between the master cylinder and the seal that is currently available.

Don’t depend on your partial memory of the presentation. Contact David for more current information

Emery Stora
77 Kingsley
Frederick, CO

>
> Emery,
> I now recall being at Dave's display at Elkhart where this was being discussed. Unfortunately I believe he said the source for parts has dried up.
>
> --
> Bruce Hislop
> ON Canada
> 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
> Hubler 1 ton front end
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
> My Staff says I never listen to them, or something like that
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
Bruce,

I don't know about a P30 setup, but with a regular GM MC, the bracket goes on top of the MC, not between the MC and booster. But you probably knew
that...

John
--
John Shotwell
Ridgeville Corners, OH
78 Royale Center Kitchen
Web Site: GMCmhRegistry.com
Email: john at gmcmhregistry dot com
 
John said:
"I don't know about a P30 setup, but with a regular GM MC, the bracket goes on top of the MC, not between the MC and booster."

Exactly what I was thinking when I read the first post. I don't remember ever seeing any brackets BETWEEN the MC and booster on any vehicles in my
life of auto repair.
--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.
 
Bruce,

Here's a photo of the seals that go between the master cylinder and the booster:

http://www.gmcmhphotos.com/photos/g6791-brake-info.html

The cup shaped one is the OEM part. I was able to get a couple from Dr. Rebuild:

http://shop.docrebuild.com/1964-1967corvettepbshellfrontsealoriginalgm5464287or5452549.aspx

You have to lie to him to get it because he only sells to people that have Corvettes.

I answered his questions with the following responses:

ADDITIONAL INFORMATION:

What EXACT address does the credit card bill arrive at in the mail: 2284 GEMINI ST., HOUSTON, TX 77058

I have read the Shipping & Policy Agreement: YES

Some c/cards will not authorize if the numbers on the rear is not entered into the c/card terminal. In the USA we will call you if
your card is declined for this #. International emailed. : 123

For 48 US states only: I understand $1.80 is added for insurance plus $.75 for each $100 value thereafter. HI, AK & International
are billed at actual rates.: YES

What brand AND model vehicle are you ordering for?: CHEVROLET CORVETTE L75

What year(s) are you ordering for?: 1964

Specify: HP, engine size, trans, AC, color, body style as needed for these parts: 300 HP, 327 CU IN, 4 SPEED, NO AC, BLUE, HARDTOP

YES or NO: Did you bother to READ the description of the items ordered? (1): YES

YES or NO: Are these parts intended for NCRS judging, evaluation or criteria? (1): NO

Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808


-----Original Message-----
From: Gmclist [mailto:gmclist-bounces] On Behalf Of Bruce Hislop
Sent: Sunday, November 5, 2017 10:35 AM
To: gmclist
Subject: [GMCnet] Seal between P30 MC and booster.

So before bleeding the brakes after installing the new caliper, I wanted to check the clearance on the MC push-pin. I loosened the
MC move it out of the way. I can see there is water leaking into the nose area between the MC and the booster (rust!). I have a P30
MC with the support bracket between the MC and the booster. There does not appear to be anything to seal water out of this area.
Especially with that bracket in between.
Am I missing a seal here? There is a rubber piece in the booster around the push-pin, but it appears to be too far in to mate to
the M/C.
--
Bruce Hislop
 
Terry,
There are lot of the p30 master cylinder units that sandwich the bracket as
it is easier to do so and it has not created problems as the amount the
effect on the pin length.

> John said:
> "I don't know about a P30 setup, but with a regular GM MC, the bracket
> goes on top of the MC, not between the MC and booster."
>
> Exactly what I was thinking when I read the first post. I don't remember
> ever seeing any brackets BETWEEN the MC and booster on any vehicles in my
> life of auto repair.
> --
> Terry Kelpien
>
> ASE Master Technician
>
> 73 Glacier 260
>
> Smithfield, Va.
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502
 
Well that is good to know, Jim. I actually never had to work on the MC in a P30 truck and I would have thought that it would make a vacuum leak unless
the bracket completely encircled the nose of the MC. Ran into the pin length problem on other vehicles before but never even considered using the
bracket as a spacer because in all the cases of interference were solved with a another MC or booster that was slightly different, but most of the
replacements were still the same part number. When the store delivers your parts, you don't get to compare them beforehand, so sometimes you have to
run around the tree again... :d
--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.
 
> So before bleeding the brakes after installing the new caliper, I wanted to check the clearance on the MC push-pin. I loosened the MC move it out
> of the way. I can see there is water leaking into the nose area between the MC and the booster (rust!). I have a P30 MC with the support bracket
> between the MC and the booster. There does not appear to be anything to seal water out of this area. Especially with that bracket in between.
> Am I missing a seal here? There is a rubber piece in the booster around the push-pin, but it appears to be too far in to mate to the M/C.

Not sure if all "p-30" masters have a groove like the original did so the original seal may not fit anyway.
http://www.gmcmhphotos.com/photos/g6732-booster-seal-and-shim.html
http://www.gmcmhphotos.com/photos/g6732-booster-seal-and-shim.html

This p-30 did not have a groove for an original style seal
http://www.gmcmhphotos.com/photos/g6798-p-30-master-cylinder-disassembled.html
http://www.gmcmhphotos.com/photos/g6798-p-30-master-cylinder-disassembled.html

--
Wally Anderson
Omaha NE
75 Glenbrook
Megasquirt III injection
Bob Stone hydroBOOOOST
Manny reaction arm system
Branscombe Kelsey Hayes park brake
http://wallyandsue.blogspot.com/
 
Wally,
Thanks for the photos and write-up. Both the old and new booster has just a flat seal, no cup.

Not sure how the water stays out without a seal, especially with the bracket in between. I also see why some type of drain is needed in case of a MC
leak so that the fluid does not get into the booster.
--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
Hubler 1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
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