[Spits] brake bleeding help

[Donald H Locker]

The PDWA - "Pressure Differential Warning Actuator" - is just a switch which detects a difference in pressure (Pressure Differential) between the rear and front circuits and Actuates the Warning (light.) The only thing it blocks is rear fluif [sic] from getting to the front if the front circuit is leaking and front fluif [sic] getting to the rear if the rear circuit is leaking. It does not prevent fluid from flowing from the master cylinder to the individual front or rear circuits.

If the brake light stays on, the shuttle may be stuck off-center, though I doubt that. (There is a lot of force available to move it if needed.) The amount of pedal pressure required to center the shuttle is very small. I used to do it with my fingertips and could feel the shuttle move.

When bleeding, don't worry about the brake light. Just finish getting all the air out. Then center the shuttle and you should be good to go. (And stop as required.)

Donald.

----- Original Message -----
> From: "Dennis Reese" <dennis_reese at wavecable.com>
> To: "Spitfire Group" <spitfires at autox.team.net>
> Sent: Thursday, May 22, 2014 1:14:32 AM
> Subject: [Spits] brake bleeding help
> 
> After installing new brakes front and rear I've been a bit frustrated
> bleeding
> the system. The rear brakes seem to be OK but  can't seem to get much more
> than air out of the front (new calipers, rotors, and hoses). Here's my
> question: If the PDWA shuttle isn't centered does that mean that the circuit
> is blocked and therefore won't allow brake fluid through? Also, the brake
> light is on but not the oil light and doing the reset per the manual doesn't
> seem to have any effect. Brake light stays on.
> 
> Any thoughts? Thanks in advance for the usual great advice.
> 
> Dennis Reese
> 75 Spitfire 1500
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