Subject: [TR] TR3A Brakes Locking Up

From: Joe DeMuth <[email-masked]>
Date: Sun, 07 Jun 2015 08:18:25 -0500

Can anyone think of a reason that the front calibers would lock up by themselves without the brake pedal being depressed. This just happened yesterday to one of out local club members who is currently with a group of other British cars circumnavigating Lake Superior. The brakes have been working flawlessly for a couple of years. He is back on the road now, and hoping the problem does not re-occur. In the meantime, I told him those of us at home would try come up with reasons/solutions for him. Any ideas?

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From: "Randall" <[email-masked]>
Date: Sun, 7 Jun 2015 08:02:41 -0700

> Can anyone think of a reason that the front calibers would 
> lock up by themselves without the brake pedal being 
> depressed.

One possibility is that the MC piston does not return fully, so the little valve in the bottom of the MC bore doesn't open.  That
can be caused by lots of things, including a sticking pedal, misadjusted pushrod, or broken "wavy" spring inside the MC.  Or the
internal rod that opens the valve might have come out of the clip that holds it to the piston.  When essentially the same thing
happened on Stag #2, the MC piston was binding in the bore due to some previous damage (DPO must've been part gorilla).  The brakes
worked fine until the fluid got hot and expanded a little.  With the return valve closed, the expanding fluid caused the brakes to
drag, which caused more heat and so on.

A quick roadside test is to loosen the fitting at the outlet of the MC and let a few drops of fluid out.  If the brakes immediately
release, the MC was probably the problem.  If not, then Mike's theory about the swollen hose, or an issue with the residual pressure
valve (on top of the 5-way connector) is more likely IMO.

-- Randall