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

["Rich Barber" <c300@xxxxxxx>]

On a '55, the manual says "If adjustment is made while unit is installed on
car-slide a scale next to boot (inside of pedal bracket up to and against
dash panel) and measure back to centerline of clevisd pin.  This distance
should be 8 57/64 inches.  If adjustment is made before unit is installed on
car, measure from reinforcing plate mounted on unit to centerline of clevis
pin hole.  This dimension should be 8 61/64 inches, as indicated in Figure
89.  See Manual pages 95-97 at:
http://www.jholst.net/55-service-manual/brakes.pdf   

 

Rich Barber 

 

From: Michael Moore [mailto:mmoore8425@xxxxxxx] 
Sent: Monday, August 13, 2012 1:26 PM
To: Rich Barber
Cc: 'Narve Nordanger'; Chrysler300@xxxxxxxxxxxxxxx
Subject: Re: [Chrysler300] A serious 55 Kelsey Hayes issue - brake failure

 

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%40yahoogroups.com>
[mailto:Chrysler300@xxxxxxxxxxxxxxx <mailto:Chrysler300%40yahoogroups.com> ]
On
Behalf Of Narve Nordanger
Sent: Sunday, August 12, 2012 12:33 PM
To: Chrysler300@xxxxxxxxxxxxxxx <mailto:Chrysler300%40yahoogroups.com> 
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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