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Mystery revealed! Residual Pressure valve

To: ZinkZ10C@aol.com
Subject: Mystery revealed! Residual Pressure valve
From: Scott Tilton <sdtilton@yahoo.com>
Date: Wed, 25 Sep 2002 04:12:18 -0700 (PDT)
Cc: triumphs@autox.team.net
Well I took the guts out of the residual pressure valve last night.

Just like Dave Massey said:  couple of springs and plunger inside.

For those curious to see . . . a picture is posted here:

http://www.imagestation.com/album/?id=4291322581

I don't know if my was broken, defective, installed wrong or what. . but it was
most certainly not functioning correctly.  

The brakes used to drag like all hell.
I could take my foot off the pedal after stopping and the car would hold itself
still, even on a slight incline.  Eventually after a minute of engine
vibration, the brakes would let go enough for the car to drift.

I always had people beeping at me at stoplights to tell me my brake lights
didn't work.

SURE THEY do . . . I just don't have my foot on the brake!

I knew they weren't ALWAYS dragging because I had coasted to a stop before and
could open the door and move the car with a push of my foot.  

Not knowing about the RPV, I had rebuilt calipers in the past trying to solve
the problem.  All to no avail.  One day when I swapped calipers between the 6
and the 4, and the dragging stayed in the TR4 . .I knew it wasn't the calipers.

This list told me long ago about the RPV . . . but I never got around to
disabling it.

What an amazing difference there is without the valve in there.

I'm sure that little gizmo was restricting fluid flow in both directions.


Let's see . .what's next on the list?  Water Pump noise, grounding steering
column for the horns, Overdrive switch, car pulls to the left, rattling gear
shifter, 100 other things.

Thanks for the help guys.

Scott Tilton
Holding his foot on the brake pedal at stoplights around
Leesburg, VA




--- ZinkZ10C@aol.com wrote:
> In a message dated 9/24/02 9:56:19 AM Eastern Daylight Time, 
> 105671.471@compuserve.com writes:
> 
> << Scott, this is called a "residual pressure valve" and it's job is to
>  maintain a modest amount of pressure on the calipers to avoid the dreaded
>  piston kickback.  Many folks, tired of servicing these things, remove the
>  internals and run direct without severe concequences.  In fact, later model
>  cars (eg: TR6) do not even have them. >>
> 
> For most cars ( not TR specific) , the RPV is located inside the master 
> cylinder outlet.  A rpv is a good idea for drum brakes as this keeps the 
> wheel cylinder seals flared outward. ( this prevents leaks) Most ( all?) cars
> 
> do not have a RPV for the disc brakes.  
> 
> Racing brake companies have 2 PSI units for disc brakes and 5PSI ( possibly 
> 10) units for drum brake systems.   
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