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Post By MOTORHEAD
12-01-2015, 05:57 AM
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CC Member
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Join Date: Feb 2001
Location: BRADENTON,
FL
Cobra Make, Engine: KIRKHAM 427 S/C, SHELBY 427 ALUM. STROKER
Posts: 1,396
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Not Ranked
Rear brakes lock-up
It would appear my rear brake master cyl is not releasing pressure when you release the pedal. This is in the original style pedal box set-up. I'm pulling things apart to gain access (not easy), but thought I'd post here to see if anyone with a Kirkham or original had a similar experience and might have some helpful tips.
Ted
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"When Injustice becomes Law,
Rebellion becomes Duty." T. Jefferson
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12-01-2015, 08:12 AM
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CC Member
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Join Date: Feb 2014
Location: White City,
SK
Cobra Make, Engine: West Coast, 460 CID
Posts: 2,916
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One possibility is a problem with the residual pressure valve. They're installed whenever the master cylinders are lower than the brake caliper and, for disk brakes, supposed to retain 2 PSI in the lines. If that valve is sticking or defective it won't allow the pressure in the rear brake lines to drop after application of the brakes.
It will look like this picture (or very similar) and be installed inline on the line between the MC and the rear brakes.
I would think they're pretty simple and reliable, but perhaps some debris was in the system and lodged in the valve. I don't know if they're repairable, but they're relatively inexpensive and easy to replace, though you will need to bleed the rear brakes when you're done.
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Brian
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12-01-2015, 08:15 AM
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Full Blown Member
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Join Date: Sep 2008
Cobra Make, Engine: KMP 427 S/C, Twin Paxton 511 FE
Posts: 2,594
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No problem with brakes here but I did replace my clutch master. I remember it being a pain. I took a wrench, heated and bent it so I could reach around the cylinder to the higher bolt. Its the the typical Cobra job - simple but hard to get to.
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rodneym
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12-01-2015, 09:02 AM
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CC Member
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Join Date: Dec 2003
Location: Gurnee,
IL
Cobra Make, Engine: Kirkham #259
Posts: 1,396
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If you have a Residual valve in the rear brake circuit.......remove it ...it is not needed and can cause issues all of the time.....
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Morris
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12-01-2015, 09:54 AM
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CC Member
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Join Date: Feb 2002
Location: Dadeville,
AL
Cobra Make, Engine: Sold my EM.
Posts: 2,459
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I know nothing about Kirkhams, but if it has a balance bar setup, I'd check that.
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Tommy
Cheetah tribute completed 2021 (TommysCars.Weebly.com)
Previously owned EM Cobra
"Never attribute to malice that which is adequately explained by stupidity." - Hanlon's Razor
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12-01-2015, 10:37 AM
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CC Member
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Join Date: Apr 2009
Location: Little Rock area,
AR
Cobra Make, Engine: ERA Street Roadster #782 with 459 cu in FE KC engine, toploader, 3.31
Posts: 4,533
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Quote:
Originally Posted by Tommy
I know nothing about Kirkhams, but if it has a balance bar setup, I'd check that.
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And make sure your brake pedal is returning fully upon release and not hung up on carpet or something.
Can't see why a residual pressure valve would be necessary. |
12-01-2015, 10:53 AM
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CC Member
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Join Date: Feb 2014
Location: White City,
SK
Cobra Make, Engine: West Coast, 460 CID
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Okay, never mind.
I just looked at one of the Kirkham documents ( http://www.kirkhammotorsports.com/book_aoe/aoe_16.pdf) and believe there is NO residual pressure valve installed.
Today I learned something, so it's a good day.
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Brian
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12-01-2015, 11:59 AM
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CC Member
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Join Date: Feb 2001
Location: BRADENTON,
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Cobra Make, Engine: KIRKHAM 427 S/C, SHELBY 427 ALUM. STROKER
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Just got back home. Thanks for the replies. No residual valve. Need to remove carpet,& sound/heat mat to get top pedal box cover off. Think it's the bottom cyl. May need to remove inner wheel well panel to access lines.
Ted
__________________
"When Injustice becomes Law,
Rebellion becomes Duty." T. Jefferson
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12-01-2015, 03:16 PM
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Full Blown Member
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Join Date: Sep 2008
Cobra Make, Engine: KMP 427 S/C, Twin Paxton 511 FE
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Ted, can't you just open the panel at the bottom?
I don't remember off hand it being that crazy down there.
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rodneym
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12-01-2015, 05:36 PM
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Join Date: Feb 2001
Location: BRADENTON,
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Cobra Make, Engine: KIRKHAM 427 S/C, SHELBY 427 ALUM. STROKER
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Rodney: The bottom plate allows some access, but not enough. Need to hold top bolt head which is accessable thru the top plate, remove vent to access sidepipe bolts, remove side pipe to see what I was doing fwd of the box, disconnect lines. That all allowed me to remove the MC. Found area outboard of the piston was contaminated with some rusty coating and jamming the piston from returning to the "off" position. Will try to post photos later
Ted
__________________
"When Injustice becomes Law,
Rebellion becomes Duty." T. Jefferson
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12-02-2015, 06:06 AM
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CC Member
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Join Date: Feb 2001
Location: BRADENTON,
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Cobra Make, Engine: KIRKHAM 427 S/C, SHELBY 427 ALUM. STROKER
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Some pics, I hope!
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"When Injustice becomes Law,
Rebellion becomes Duty." T. Jefferson
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12-02-2015, 06:22 AM
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Stolen Avitar
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Join Date: Oct 2004
Location: Brunswick,
GA
Cobra Make, Engine: BDR 1311 428PI
Posts: 3,044
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Wow, and I thought BDRs were a hassle!
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12-02-2015, 07:01 AM
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CC Member
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Join Date: Feb 2014
Location: White City,
SK
Cobra Make, Engine: West Coast, 460 CID
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Those photos clearly show low-mounted master cylinders, different than I saw yesterday in the Kirkham document I looked at ( http://www.kirkhammotorsports.com/book_aoe/aoe_16.pdf) - perhaps that document relates to later production.
Regardless, given the low mount, there s/b a residual pressure valve somewhere in the rear brake line, unless there's one built in to the MC. Even if it's not the source of the current problem, it's worth knowing where it is.
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Brian
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12-02-2015, 07:29 AM
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Join Date: Feb 2001
Location: BRADENTON,
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Cobra Make, Engine: KIRKHAM 427 S/C, SHELBY 427 ALUM. STROKER
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If I remember (which I don't do very well anymore)correctly, working thru the side vent hole was the trick on theBDR's.
Brian: believe me, I have re-built this car down to bare chassis/body (well, partial body), and there is no residual pressure valve on it anywhere. Besides, the sticking MC piston was the culprit. This is a very early Kirkham, sn 0028, built in 1998.
__________________
"When Injustice becomes Law,
Rebellion becomes Duty." T. Jefferson
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12-02-2015, 07:35 AM
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CC Member
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Join Date: Feb 2001
Location: BRADENTON,
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Cobra Make, Engine: KIRKHAM 427 S/C, SHELBY 427 ALUM. STROKER
Posts: 1,396
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Brian: the car in the book you referred to is the Larry Elison "billet" Kirkham, built for 1mil
a few years ago. A totally different animal !
__________________
"When Injustice becomes Law,
Rebellion becomes Duty." T. Jefferson
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12-02-2015, 07:49 AM
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CC Member
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Join Date: Feb 2014
Location: White City,
SK
Cobra Make, Engine: West Coast, 460 CID
Posts: 2,916
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Quote:
Originally Posted by MOTORHEAD
Brian: the car in the book you referred to is the Larry Elison "billet" Kirkham, built for 1mil
a few years ago. A totally different animal !
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"A totally different animal!"
Agreed - both the car and Larry.
__________________
Brian
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