Brake work - caliper caution

[Matt Colie]

I have recently torn down a friends master cylinder to find it not damaged, but full of foreign material in the high pressure seals.

Because I am working to make a 95 Accord safe to drive again, I was watching YouTubes about front bearings. (The bearing has failed and so damaged
one brake.)

In the section I was watching, the technician demonstrated that he always clamps off the line to the caliper and vents the fluid out the bleeder. As
Greg's coach recently had front brake work and then the master cylinder failed (I mean failed big time - peddle to the floor, but no fluid lost!) I
am willing to accept this as a cause.

When I come up for air, I plan to rebuild the good casting and put it on the shelf.

Matt - Break is over, back on my head
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit

 

[Rdenney]

how Did the foreign material get in there? Doesn’t bench bleeding clear
such out of a fresh master cylinder? What does clamping the lines to the
wheels do?

Rick “not understanding” Denney

On Fri, Nov 1, 2019 at 12:03 PM Matt Colie via Gmclist <

> I have recently torn down a friends master cylinder to find it not
> damaged, but full of foreign material in the high pressure seals.
>
> Because I am working to make a 95 Accord safe to drive again, I was
> watching YouTubes about front bearings. (The bearing has failed and so
> damaged
> one brake.)
>
> In the section I was watching, the technician demonstrated that he always
> clamps off the line to the caliper and vents the fluid out the bleeder. As
> Greg's coach recently had front brake work and then the master cylinder
> failed (I mean failed big time - peddle to the floor, but no fluid lost!) I
> am willing to accept this as a cause.
>
> When I come up for air, I plan to rebuild the good casting and put it on
> the shelf.
>
> Matt - Break is over, back on my head
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan
> OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
'73 X-Glacier 230 "Jaws"
Northern Virginia
Offlist email: rick at rickdenney dot com

 

[Larry Davick]

Are you suggesting that clamping the hose caused it to fail internally? Do you think the crap in the master cylinder came up from the hoses?

(pardon my French)
--
Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy

 

[Matt Colie]

I don't know where the stuff that fouled the master cylinder came from, but a caliper would not be any surprise. I plan to research this as a part of
they brake job that is in process here. (If I can make the bearing come out of the knuckle.)

Matt

--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit

 

[sgltrac]

I don’t know how crud would go up into the master. Unless the system was
super contaminated and it was bled in reverse?

???

Sully
Bellevue wa

On Fri, Nov 1, 2019 at 2:53 PM Matt Colie via Gmclist <

> I don't know where the stuff that fouled the master cylinder came from,
> but a caliper would not be any surprise. I plan to research this as a part
> of
> they brake job that is in process here. (If I can make the bearing come
> out of the knuckle.)
>
> Matt
>
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan
> OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[Matt Colie]

> I don't know how crud would go up into the master. Unless the system was super contaminated and it was bled in reverse?
>
> ???
>
> Sully

Sully,

Coaches tend to be way older than most passcars out there. So crud accumulating in a caliper is very possible.
And, yes, when you compress a caliper to replace the brake pads, you are reverse bleeding it. Albeit unintentionally so.

Greg's coach fits in the category of massively ignored for decades.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit