Hello, Dennis.
Brakes are pretty simple systems, so look for fluif [sic] going where it
shouldn't, air in the pipes, or oil on the pads/rotors/drums and you will find
the problem.
Of course, clean and grease-free friction surfaces are a must; from your note,
this doesn't sound like an issue as the brakes do work after pumping.
If you eventually get some pedal firmness after pumping a bit, the most likely
problem is air in the pipes. This requires bleeding to correct. If you've bled
from all four corners and still have a soft pedal, I would recommend doing it
again, but using a different technique. Use a three-foot/one metre length of
clear vinyl tube and raise it high instead of putting it down into a catch
bottle. Watch the air in the fluid rise in the tube as you pump the pedal
gently. When no more bubbles rise, you can close the bleed screw. Because the
fluid in the tube keeps air away from the bleed screw, you don't have to have
one person operating the pedal and one working the bleed screw. The presence of
the bubbles (to my old eyes, at least) is much more clear with the vinyl tube.
It is also possible, if this is a recent rebuild, that the brakes are not yet
adjusted. The fronts are self adjusting, and the pads will move to the rotor
and establish their operating position with a few real actuations. If the rears
are not well-adjusted, they can reduce total performance, but not as much as
the front. If both are out, you will have some trouble for a while. Try pumping
up the pressure several times and see if the pedal improves before going out
for the next drive. Then make sure the rears are correctly adjusted.
The PDWA is often blamed for brake problems - if it leaks fluid to the outside
world, that is a problem. Otherwise, it really can't affect braking
performance. It is a high-pressure differential pressure switch. If the
pressure on the front circuit is significantly different that the pressure in
the back circuit, the switch turns on the light. The shuttle moves, but DOES
NOT change anything in the hydraulics.
Hope this helps.
Donald.
----- Original Message -----
> From: "Dennis Reese" <dennis_reese@wavecable.com>
> To: "Spitfire Group" <spitfires@autox.team.net>
> Sent: Saturday, June 28, 2014 2:09:53 PM
> Subject: [Spits] Brake system?
>
> I have just finished with new brakes all around on my 75 Spit. Everything
> seems to be OK, but I have very little to "no" pedal. Goes to the floor and
> after a couple of pumps the car stops - sort of. What am I missing? New
> master
> cylinder? If so, which. Moss and VB both seem to sell the Lucas/TRW variety
> for something like $200 and another aftermarket thing for about $100 less.
>
> Rest assured I am not out on the highway with this thing -- just up and down
> our 1/2 mile driveway.
>
> Any advice is always appreciated.
>
> Dennis Reese
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