<VV> Weak brake action

[Charles McKinley]

Thanks very much for all the helpful suggestions sent in by a whole  
bunch of you in response to my query below. Now there's a new wrinkle  
- I've discovered that I'm losing brake fluid from the master cylinder  
even when the car is parked in the garage (which has been almost all  
the time the last few weeks.) It takes about a week for the cylinder  
to drain from topped up to almost the bottom of the reservoir. It  
appears to be leaking from the back of the master cylinder, where the  
brake pedal rod goes in. For what it's worth, the rubber boot that's  
supposed to be on the rod is absent - don't know if that got missed  
when I did the rebuild a dozen years ago, or if it got eaten by brake  
fluid, but it's just gone. Also for what it's worth, I never had this  
problem (fluid leakage) before I went through all the exercises  
described below to try to fix the brake action problem, and I wonder  
if I might have popped a seal in the master cylinder with hundreds of  
hard pumps on the pedal to check the action. There's no sign of  
leakage at any of the joints between brake lines, hoses, or wheel  
cylinders, and the action is still very solid as descibed below, so  
I'm focused on the master cylinder. Here's my question: would I be OK  
to do another rebuild of the MC (for about $30) or would it be smarter  
to spend about $70 for a complete new MC? I'm leaning toward the  
latter, but would like to hear your thoughts.

Thanks in advance,

Chuck



On Dec 4, 2009, at 11:58 AM, Charles McKinley wrote:

> I'm a little embarrassed about asking this, as it seems like a  
> moronic question, but I'm at a loss as to where to go next. I've had  
> a '63 Monza 900 for about 16 years now, and in all that time, the  
> braking action is what I'd call puny - maybe I've gotten used to the  
> power brakes in every other car I've owned for 40+ years, but it  
> really doesn't feel right. The symptoms are that when I apply the  
> brakes, they do work, but I have to apply more pressure than I think  
> should be necessary, and there's no such thing as a panic stop - I  
> can't jam on the brakes and screech to a halt (that's the most  
> worrisome part.)
>
> Recently I've done the following in an attempt to fix this:
>
> - had all drums turned
> - put in all new brake shoes
> - put in all new wheel cylinders
> - put in new brake line hoses
> - installed new return springs
>
> Long ago I rebuilt the master cylinder.
>
> The brake pedal is very solid - no fading, solid stop with minimal  
> depression
>
> I have a complete set of new brake lines, but when I learned you  
> have to drop the motor and remove the gas tank to install them, I  
> decided to hold off until I have a more compelling reason to do  
> either of those chores.
>
> I've bled the master cylinder and the wheel cylinders until I'm blue  
> in the face, with no improvement.
>
> The only items left in question (that I can think of) are:
> - master cylinder problem of some sort (can't think what)
> - old brake lines being a little plugged (although I get plenty of  
> flow when bleeding the wheel cylinders)
>
> Any suggestions?
>
> Thanks in advance,
> Chuck McKinley