[Chrysler300] UPDATE- Problems with AAJ power disc brakes on a C300
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[Chrysler300] UPDATE- Problems with AAJ power disc brakes on a C300



First of all thank you for all the thoughtful replies, feedback and tips.
The goal of my change is safer and better braking in today?s traffic before
I head to Santa Monica on Route 66.


The general consensus is that the new (Chevy) boost unit is defective and/or
underperforming. There is some concern about the lack of vacuum available in
our 300?s due to the aggressive cam. We are in the process of evaluating the
vacuum situation and a new booster is in the mail from AJJ. I should add
that Roger at AAJ has been helpful and is helping diagnose and remedy the
situation. I will update the group with our final findings and write up the
conversion process after all the dust settles and everything is working


Lastly, several members have commented about their cars, other than a ?55.
The ?55 only K-H unit presents a unique set of conditions and no valid
comparison to later cars. While they are interesting they are not very
helpful to my situation. There were several best practices offered to make
the most of the drums and shoes and those were interesting and helpful. I
will state for comparison that my dad?s ?57 New Yorker stopped MUCH better
than my ?55 ever has in 49 years and 100,000 miles. In my opinion, Chrysler
made a wise decision in going back to a traditional MC in 1956. That said, I
am keeping and identifying all the old parts so they can go with the car
when I can no longer drive it. It would take a good man with a limber back
and neck about a day to put it all back 100% stock.


Thanks again and stay tuned for the final resolution and summary in a few





Jack Boyle

(913) 544 4650


Enjoying the same C-300 since 1967

IMG_0623 small




From: Jack Boyle [mailto:jackcboyle@xxxxxxxxx] 
Sent: Monday, March 6, 2017 7:13 PM
To: Chrysler300@xxxxxxxxxxxxxxx
Subject: Problems with AAJ power disc brakes on a C300


I just finished installing a disc set up from AAJ on my C300. There were
some bumps along the way but it?s finally complete. Now I am having poor
braking performance. The symptoms are primarily weak braking with both feet
on the pedal ? and no lock up, not even a chirp.  It?s like I don?t even
have power brakes. The pedal is as hard as a rock and never even gets close
to the floor.


Roger at AAJ and my local old Mopar expert have offered some suggestions but
before I act on those I wanted to poll the group.


Here is what I have done to date:


1.     New DOT 5.1 all around (glycol type with low moisture absorption)

2.     Bench bled the MC per instructions

3.     Found one line leak and fixed it (defective NEW! fitting)

4.     Adjusted the rear drums as close as possible

5.     Checked the booster vacuum line for obstructions

6.     New stiff factory dia. Vacuum Hose with no leaks

7.     Vacuum tests at 14 inches, 15 max. (damn cam)

8.     Bled all wheel cyl. 3 times starting with the RR

9.     Tried all ranges of the proportioning valve setting, including closed
off completely (best braking is with valve open ¾ turn)


Still a rock hard pedal and VERY marginal braking performance.


Any tips, questions, fixes, etc. welcome.


Thanks  ?Jack


Jack Boyle

(913) 544 4650


Enjoying the same C-300 since 1967

IMG_0623 small


[Non-text portions of this message have been removed]

Posted by: "Jack Boyle" <jackcboyle@xxxxxxxxx>

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