Re: [Chrysler300] A serious 55 Kelsey Hayes issue - brake failure

[Michael Moore <mmoore8425@xxxxxxx>]

Rich,
That is the clearance which my 62 shop manual makes a point about being dealer adjustable only. I have had master cylinders replaced over the years, and my pedal was very low although the brakes worked. 

I decreased that clearance from ca .150 down to .060 which got my pedal up substantially (because of the multiplier effect between the pedal to pedal pivot compared to the distance between the pedal pivot and master cylinder linkage) , but I have never found reference as to how much clearance the factory specified. 

My 63 Jaguar has a similar setup, but it is a lot easier to adjust so I just kept releasing mine until it didn't seize up any longer.
Does anyone know how much clearance was factory specified?
Mike Moore
300H 

On Aug 12, 2012, at 1:20 PM, Rich Barber wrote:

Narve:

I know you are a thorough guy, but the clearance on the actuating rod from
the brake pedal to the back of the booster is critical. In theory,
retraction of the rod when the pedal is released should allow atmospheric
pressure to flow back into the vacuum side of the booster. If the pedal is
returned by spring pressure, it should retract the actuator rod.

There is a small check valve in the outlet of the master cylinder that is
designed to hold a small amount of residual pressure on the system in order
to exclude moist air. That small check valve may have been damaged or
improperly installed.

Other things to check include the check valve on the vacuum inlet line.

Progress was made over the years. The brake pedal in the '55 is now wide
enough to get both feet on it.

Rich Barber

Brentwood, CA

1955 C-300

From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On
Behalf Of Narve Nordanger
Sent: Sunday, August 12, 2012 12:33 PM
To: Chrysler300@xxxxxxxxxxxxxxx
Subject: [Chrysler300] A serious 55 Kelsey Hayes issue - brake failure

Group,

my C-300 has twice this summer had failure on its freshly overhauled brake
system. On both occasions the Kelsey Hayes master power brake appear to lock
up and not letting out the vacuum after I have released the brake pedal.
Brakes stayed locked until I split the master cylinder from the booster.
Anyone seen this before, any remedy?

Additional information: The lightest of touches on the brake pedal sucks it
in and make immediate contact on the shoes, making progressive braking a
difficulty. This was evident both with the old (original) and overhauled
(x-55 De Soto) K-H MC. Having just gone through the brakes on 29 Chrysler
one really wonders if there was any progress at all in the intervening 26
years..

Narve N

C-300 in Norway

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