Ron--
Thanks for the good tip. Though the failure mode you describe does not
correlate exactly with my experience in case the MC is up for removal,
inspection and rebuild. Until then the 100's driving privileges have been
suspended.
Best--Michael
On Mon, Apr 30, 2012 at 11:02 AM, Ron Mitchell <healeyron at yahoo.com> wrote:
> Hi Michael,
>
> There is a small hole that is located directly in front of the pressure
> seal called a Compensating Port that allows fluid to flow into the master
> cylinder from the Fluid Reservoir. After much use the lip of the seal will
> develop a small groove where it rubs over the port as you apply the
> brakes. In time that groove will become deep enough that under pressure
> the seal doesn't expand enough in the area of the groove to seal off the
> bore and will freely travel forward. Until the groove gets big enough to
> be a complete failure you will experience the described problem on light
> applications of the brake pedal. If you apply the brake pedal firmly the
> seal will expand positively against the the bore but fluid will slowly
> bypass the seal as the seal relaxes. The symptoms you describe sounds
> like that may be the problem. You can sometimes evaluate this condition if
> you get someone to remove the Reservoir Cap and watch for a slight blip of
> fluid as you slowly apply the brake pedal.
>
> Hope this helps,
> Ron Mitchell
> BN6
> BN7
>
>
>
> ------------------------------
> *From:* Michael Oritt <michael.oritt at gmail.com>
> *To:* Austin Healey <healeys at autox.team.net>
> *Sent:* Monday, April 30, 2012 7:17 AM
> *Subject:* [Healeys] Brake problem
>
> Yesterday while returning from a ride in the 100 I applied the brakes and
> the pedal went to the floor--fortunately the emergency brake slowed me down
> enough that I could negotiate the upcoming turn and come to a stop.
>
> After a few deep breaths I stepped on the brake pedal--this time it was
> normal and the brakes functioned seemingly fine. I checked the hydraulic
> fluid reservoir and it was full. I was less than a mile from the garage so
> returned slowly though the brakes continued to work fine and got me back.
>
> In the garage I applied the brakes a few more times, all normal except for
> one time when I held my foot on the pedal it and it went slowly to the
> floor like I was pushing fluid out somewhere through a very small leak but
> there were no leaks. Next push the brake pedal was high and firm. Retested
> several times at 15 to 30 minute intervals--no problems, but obviously
> something is wrong here!
>
> I haven't pulled the master cylinder off and apart yet but am thinking that
> the return valve is somehow hanging up. FWIW I have a BT7 discs in front
> and drums in back and a single circuit setup with a valve in the rear brake
> line which serves as a poor man's proportional setup.
>
> Thoughts?
> Best--Michael Oritt
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