Steering, Suspension, & Brakes

tips, technology, tools and techniques related to non-driveline mechanical components

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coolmgcma
Mark Cooley

(15 posts)

Registered:
12/10/2010 04:44PM

Main British Car:


Front Calipers locking up
Posted by: coolmgcma
Date: May 30, 2015 03:57PM

Finally got around to driving my newest creation and found after a few miles that the both front calipers lock up and the peddle gets hard as a rock. I have Wilwood calipers, pads and rotors. The master cylinder and booster are from Summit Racing, the fit was great and another friend of mine is using the same set up with success. After the car sat for 20 minutes everything freed up and worked as advertised, any thoughts please.



Edited 1 time(s). Last edit at 05/31/2015 09:22AM by MGBV8.


mgb260
Jim Nichols
Sequim,WA
(2013 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Front Claipers locking up
Posted by: mgb260
Date: May 30, 2015 05:38PM

If it was just one side I'd guess the flexible line was collapsing inside. Do you have a combination valve or proportioning valve? Also you need a little free play at the pedal, should be able to wiggle the master cylinder pushrod.



Edited 1 time(s). Last edit at 05/30/2015 05:40PM by mgb260.


coolmgcma
Mark Cooley

(15 posts)

Registered:
12/10/2010 04:44PM

Main British Car:


Re: Front Claipers locking up
Posted by: coolmgcma
Date: May 31, 2015 07:04AM

No proportioning valve, and about 1/8 inch of free play. Could air in the line get hot, expanding and cause this condition?


Orange Alpine
Bill Blue

(45 posts)

Registered:
12/20/2010 07:36AM

Main British Car:
1967 Sunbeam Alpine 2.5 Ford Duratec

Re: Front Claipers locking up
Posted by: Orange Alpine
Date: May 31, 2015 08:00AM

As I see the situation (it happened to me), the only way brakes can lock up is if fluid gets trapped in the system and cannot return to the reservoir. As it heats and expand, it cannot return to the reservoir and pressure builds. Trapped air would not cause the problem in a properly operating system.

Jim is correct about the free play, but it is also possible the front piston sticks and does not return all the way, trapping fluid. Boosters can also be the culpret, but I know nothing about them.

Bill


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5834 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Front Calipers locking up
Posted by: BlownMGB-V8
Date: May 31, 2015 11:09AM

I had that problem on a bike once. The master cylinder was assembled with the wrong cup seal, which extended over the pressure port even when fully retracted. In that case I drilled a new port in the cylinder but the correct seal should have also fixed it.

Jim


roverman
Art Gertz
Winchester, CA.
(3006 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Front Calipers locking up
Posted by: roverman
Date: June 01, 2015 02:54PM

Is it possible Wilwood stipulates what psi residule check valve to use, if any ?


DiDueColpi
Fred Key
West coast - Canada
(1259 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
What if the Hokey Pokey really is what it's all about?

authors avatar
Re: Front Calipers locking up
Posted by: DiDueColpi
Date: June 01, 2015 03:47PM

The next time this happens, back off the nuts that hold the master onto the booster. If the brakes release then you need to adjust the clearance between the booster pushrod and the master cyl.as it's not letting the master return fully.

Cheers
Fred



NCtim
Tim Shumbera
Western North Carolina
(238 posts)

Registered:
01/19/2012 04:35PM

Main British Car:


Re: Front Calipers locking up
Posted by: NCtim
Date: June 19, 2015 05:15PM

Fred has the answer! Ding, ding. My money is on that. That happened to me on a '69 Roadrunner I put a booster on.
Tim


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