Re: {Chrysler 300} 1964 Power Braking

On Mon, Sep 15, 2025 at 5:44 AM John Grady <jkg@xxxxxxxxxxxxxxxxx> wrote:

good point by Henry about rear lines . Just use common sense air sits at high point , always.

It takes very rapid flow to make it move Downward to bleeder from frame high point .

Very simple fast answer is after normal bleeding , with bleeders closed , barely crack the fitting up on frame ( high point ) push pedal any air in upward loop comes out . Important to barely crack it so air does not go back in, little drop comes out like very slow leak

On this issue , if pedal can go to floor and no leak of fluid it is a bad master, fluid bypassing seals .

Has nothing to do with booster

The probkrm with high velocity bleeding is getting air entrapped in it by agitation and using lots of fluid , both very bad with silicone fluid. Although against the grain, ( I know) it makes no sense to me to bleed master despite instructions , air rises yo master there , vents out just fine . It is made to do that I never did it never hsd problem . How can it NOT rise up the vertical line to master and out? as it moves back and forth ?folklore, but to each his own

Aggressive bleeding adds to woes with micro bubbles once you cause them by adding fluid with silicone . Takes months to calm down if you do , repeat bleed after that time , especially high point (s)
j

On Sep 14, 2025, at 11:42 PM, henry.schleimer via Chrysler 300 Club International <chrysler-300-club-international@xxxxxxxxxxxxxxxx> wrote:

Hi Dave. Just a few tips.

Normally, if you have all the air out of the lines, your symptoms would indicate the master cylinder piston seals are letting fluid get past. Can be internal with no external leaks. Fluid level won’t drop when the pedal drops to the floor.

Possibly air stuck in master cylinder as well. Need to disconnect lines at the master and bleed that first if you let the fluid level drop too low.

I have had trouble getting air out of the rear hose at the axle as a bubble can sit in the high spot unless you are aggressive in your bleeding. Try getting your helper to give quick, forceful, full-stroke pushes when bleeding the rears. I have found a bubble that way. I assume you are bleeding with the shoes adjusted for no clearance so bubbles can’t shuttle back and forth…

Since you may have done all this, I thought I would double check one of my factory manuals for clues. In my ’71 Valiant manual under “Pedal goes to the floor” it also says “Shoe hanging up on rough platform” as a possibility. Something I hadn’t considered, but could be true if the backing plate has ridges in it.

If you can’t find the problem, please go to a reputable brake repairer. This may be a symptom of a serious failure to come.

Henry

From: chrysler-300-club-international@xxxxxxxxxxxxxxxx <chrysler-300-club-international@xxxxxxxxxxxxxxxx> On Behalf Of Robert Hayen
Sent: Monday, 15 September 2025 7:55 AM
To: Nick Taylor <nicksgaragesd@xxxxxxxxx>
Cc: David Dumais <ddume300@xxxxxxxxx>; Chrysler 300 Club International <chrysler-300-club-international@xxxxxxxxxxxxxxxx>
Subject: Re: {Chrysler 300} 1964 Power Braking

Are the shoes adjusted up against the drums properly ?

On Sun, Sep 14, 2025 at 3:52 PM Nick Taylor <nicksgaragesd@xxxxxxxxx> wrote:
Sounds like a bad master cylinder. Or the wrong one and pedal travel is not right. Which booster is on the car?

On Sun, Sep 14, 2025, 2:34 PM David Dumais <ddume300@xxxxxxxxx> wrote:
Hey Guys,
I have bled the all new brakes on the 300, many times over.

1: push pedal slowly, hold it open bleeder thru clear hose into jar.
Stiff pedal, but can be pushed to the floor after bleeding.

2: used the pistol grip vacuum hoses and cup, minute pinpoint bubbles observed.

3: wide open bleeder on a slow pedal, holding, squirt and tighten bleeder. Let pedal rise.

After all that, the pedal is firm and can be slowly pushed to the floor.
Start motor and pedal easily pushed to floor.
All the Booster Exchange guys say it's not the booster, but air still in system.

Does the Master Cylinder push rod affect this pedal down to the floor?

Still need to bleed out air?
No visible leaks on cylinders or connections.

Any clues accepted.

Dave
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