FWIW I've been reading this thread for a few days now and thought
that I had the SAME symptoms. Here's what I did. I adjusted the rear brakes
until they were tight then backed off the adjustment just a bit until the
hub were hard to move. I might add that I also HAD rebuilt the M/C and
flushed the entire system with denatured alcohol ( I used a whole
gallon!!! ) to completely flush the system. Thanks Miti-Vac !!!
To force all the alc. out of the lines I used "canned air" the
stuff used to blow dust out of your computer parts...worked great!!! I
refilled with DOT 4 for two reasons,1) it's readily available and 2) I
didn't pull and rebuild the calipers or drum pistons.
Have Good Day
Dave Gebhard
1977 Spitfire
----- Original Message -----
From: Nolan Penney <npenney@mde.state.md.us>
To: <spitfires@autox.team.net>; <pbowen@intellinetics.com>;
<Gosling_Richard_B@perkins.com>
Sent: Friday, October 13, 2000 6:22 AM
Subject: Re: RE: What's wrong with my brakes?
>
> A master cylinder can create something that looks like a pump up, but
> it really isn't. All a bad master cylinder can do is leak fluid past the
seal.
> This results in a sinking pedal. Not a low firm pedal, but one that
> creeps down. The seal will leak and the pedal will sink under mild
> brake application. Most people will not notice that the pedal is
> sinking, they will only realize the pedal is low some time after it has
> begone sinking. They will then reapply the brake, but will do so with
> much higher pedal pressure. The higher pressure pushes the seal lip
> harder against the bore, sealing it. and giving a non-sinking firm pedal,
> but only when the brake pedal is pushed harder then normal.
>
> There's a very nice article on master cylinder diagnostics at this web
page
>
http://www.babcox.com/oop/qfullhit.htw?CiWebHitsFile=%2Fbf%2Fbf109954%2Ehtm&;
CiRestriction=master+cylinder&CiBeginHilite=%3Cstrong+class%3DHit%3E&CiEndHi
lite=%3C%2Fstrong%3E&CiUserParam3=/search.asp&CiHiliteType=Full
>
>
>
>
> >>> "Bowen, Patrick" <pbowen@intellinetics.com> 10/12 11:13 AM >>>
>
> Nolan, Bad Master Cylinders will most definitely pump up. While the
> suggestions you gave are valid, most of the problems I have ever seen like
> this are the M/C.
>
> Patrick Bowen
>
> -----Original Message-----
> From: Nolan Penney [mailto:npenney@mde.state.md.us]
> Sent: Thursday, October 12, 2000 9:21 AM
> To: spitfires@autox.team.net; Gosling_Richard_B@perkins.com
> Subject: Re: What's wrong with my brakes?
>
>
>
> Being able to pump up the brakes is not normally an indicator of a
defective
> master cylinder, it's more commonly an indicator of maladjusted brake
shoes.
> It can also indicate a problem with the calipers.
>
> In any case, you're first push on the brake pedal pushes the brake
> components
> out to the drum (or against the rotor). The second pump happens faster
then
> the brake components retract. Hence the pump up. And, hence the
> repeatablilty when you give the brake components a chance to fully
retract.
>
> A bad master cylinder will not pump up.
>
>
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