Subject: Re: [TR] TR6 brake problem

From: Jeff <[email-masked]>
Date: Mon, 27 May 2013 20:54:34 -0400

On 5/27/2013 8:24 PM, triumph74tr6 wrote:
> That is exactly what it does.....closes off a perceived bad circuit.

Pretty sure that's wrong.

See http://www.vtr.org/maintain/pdwa.shtml - the piston is a constant 
diameter.  How would it shut off flow, without some careful positioning 
of the o-ring, which shouldn't easily seal a round hole in the side of 
the bore anyway.

Some look different:  http://www.74tr6.com/pdwa.htm  But I still don't 
think it's made well enough to seal against brake pressure.

I've had my PDWA illuminate many a time on my old Spitfire, and I never 
had any diminution of brakes.  Doesn't seem safe to cut off half your 
brakes for a small leak...

Jeff Scarbrough
Corrosion Acres, Ga.

** [email-masked] **

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---

From: Creig Houghtaling <[email-masked]>
Date: Mon, 27 May 2013 21:45:54 -0500

I checked the fluid flow today.  Moving from the MC down to the driver side
front wheel, had pressure/flow before the PDWA. Had pressure/flow after the
PDWA.  Had pressure/flow just before the brake flex line.  Had no
pressure/flow just past the brand new stainless braided flex line.  I took
the braided flex line off and the fluid from the brake reservoir flowed into
my catch container.  Wiped the flex hose fittings as well as I could and
blew air through the line.  Now I have a mystery.  If air goes through,
brake fluid should pass through.

Now I am defining pressure/flow at each of the above mentioned points as
this:  My friend steps on the brake pedal.  I loosen the connection till I
see fluid bleed out, and then I retighten.  That is what I got all the way
down to the connection into the flex line.  The connection of the flex line
to the short pipe to the caliper did not bleed.  I then took the female
threaded pipe connector completely loose from the flex line.  My friend
pushed on the brakes and no fluid flow.  My only guess at this point is the
orifice on the flex line is so tiny that it managed to shut down against the
brake fluid pressure.  Perhaps some foreign object got lodged.  Removing the
line and blowing air (perhaps in the opposite direction) cleared the
obstruction.  Maybe...

Stay tuned.  Tomorrow I will get the old flex lines and put one back on the
driver side.  Then I'll check to see if I have caliper on the left and not
the right.  Might try a few other things too.  Will let you know.

-----Original Message-----
From: [email-masked]
[mailto:[email-masked]] On Behalf Of Jeff
Sent: Monday, May 27, 2013 7:55 PM
To: [email-masked]
Subject: Re: [TR] TR6 brake problem

See http://www.vtr.org/maintain/pdwa.shtml - the piston is a constant
diameter.  How would it shut off flow, without some careful positioning of
the o-ring, which shouldn't easily seal a round hole in the side of the bore
anyway.

Some look different:  http://www.74tr6.com/pdwa.htm  But I still don't think
it's made well enough to seal against brake pressure.

I've had my PDWA illuminate many a time on my old Spitfire, and I never had
any diminution of brakes.  Doesn't seem safe to cut off half your brakes for
a small leak...

Jeff Scarbrough
Corrosion Acres, Ga.

Archive: http://www.team.net/archive
http://autox.team.net/mailman/options/triumphs/[email-masked]

---

From: Chad <[email-masked]>
Date: Mon, 27 May 2013 20:47:04 -0700 (PDT)

Yep.....you're right.  I'm exhausted and wrong.  :-)
 
Chad in Tulsa.
________________________________
 From: Randall <[email-masked]>
To:
[email-masked] 
Sent: Monday, May 27, 2013 9:58 PM
Subject: Re: [TR]
TR6 brake problem

PDWA = Pressure Differential Warning Actuator.  What it
does is actuate the
warning (big red light on dash) when there is a pressure
differential.  It's
not a valve at all, does not control flow at all.  The
seals are only to
keep fluid from leaking out through the switch.

Take a look
at http://goo.gl/fYlAz
You can see how both ends are turned down, so fluid can
flow freely past
even when the piston is against the side of the housing.

--
Randall 

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