Re: master cylinder

[jlandry@domain.elided (John A. Landry)]

When he stopped taking his medication, strange voices in "Abrusci, Mike
(NM75)" <mike.abrusci@domain.elided>'s head said:

>The pedal feels like it goes down too far.
>It seems to stop ok but feels a little spongy. The pedal does not go down
>with continues pressure like a bad master cylinder. 
>
>Could this still be air in the line?

With all the bleeding you've done... very doubtful.

>Does disc brakes need positive pressure out of the master cylinder?

Due to the action of the rubber o-ring seal contained inside the caliper,
disc brake calipers are designed to retract *slightly* each time the brake
pedal is released.  When the pedal is released, as far as I know, pressure
from the master cylinder is *not* maintained against the caliper.

>Do I need a disc - disc master cylinder?

I don't think so as long as you keep a close eye on the fluid level.  Disc
brakes cause the level of the brake fluid in the master cylinder to drop as
the brake pad wears.  Unlike the drum brake which (when working properly)
compensates for shoe wear with a mechanical adjuster.

>Do Internationals usually have nice hard pedals?

My 76 Traveler does now that the rotors are running true.

How about this angle Mike...

Have you replaced the brake proportioning valve?  This is the metering
block located below the master cylinder which also incorporates a brake
warning light switch.

From the IH shop manual: "The metering valve is installed with hydraulic
line to front disc brakes to delay pressure buildup to front brakes when
brakes are applied.  Its purpose is to reduce front brake pressure until
rear brake pressure overcomes rear brake shoe return springs."

So in your case Mike, you no longer have the need to overcome a heavy
return spring on the rear brakes.  So I wonder if it might be time to
purchase and install one of the variable adjustment type proportioning
valves from Summit or Jegs?  That way you can fine tune the brake bias to
suit your needs.

Also, have you checked the rotor run-out and parallelism on all of the
rotors?

Lifetime warrantee rebuilt master cylinders are *cheap*, so maybe you
should replace it for good measure... just to be sure there isn't a bad
seal in there.

Good luck and keep us posted,

John L.
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