Re: [Chrysler300] 300-F brake problems -
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Re: [Chrysler300] 300-F brake problems -

2nd post , rereading , if pedal really is "rising up " the master piston is pushing it up ,( the booster pushes the other way.. in)   and hydraulic pressure in the master cylinder bore is therefore inside it , as well as at switch and shoes. And why pedal is hard .  ( it got by the check valve ok-- as it should) Has to be GROSSLY out of mechanical adjustment to allow master to
Push the pedal up at all. Yow! Normally properly adjusted and installed  master sits at its own stop at firewall all the way out , as mentioned earlier , cannot move more ,, or lift the pedal , and relief port sits open in that position . So unless that stop has popped  out or is not there allowing master piston to come right out of master ? It might be a snap ring jumped out ?hard to believe that ?  Master , installation of it or adjustment must be way out of whack . 
If it is traveling back more than designed , it might cover up relief port again , locking all up till cools . Or just badly misadjusted = . No gap . = New master if determined to be over travel , read FSM how to adjust rod . Some are fixed length . 

Do not recall rod  details. Not " I know how" on the set up . Have guy read FSM 

Sent from my iPhone

On Jul 30, 2017, at 4:44 PM, Noel Hastalis cpaviper@xxxxxxxxxxx [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:

Hello Group,

Hi Everyone,

Welcoming your thoughts on recent braking issues my F is suffering -

Problems started last Sunday afternoon, on my 77 mile drive back home from the Belvidere, IL Mopar Happening. About halfway home, I smelled a brake shoe burning smell, and saw the engine temp gauge move up to the midway point, from its typical cool position - this while running at 70 mph with 90 degree outside temps. The brakes were clearly making contact. The brake pedal was also sitting an inch or more higher than normal, with a hard feel, but the brakes still stopped the car when applied. I backed into my garage, and noticed my brake lights stayed on, even when not touching the pedal. When I lifted up on the pedal, the brake lights would go off. I popped off the hubcaps, all 4 of which were very hot to the touch, to let the wheels cool off a little quicker. When the car cooled down, it was back to normal.

This week, I went to 3 local cruise nights, each about 15 minutes away, with no apparent braking issues. I also took the F to the local shop I've used for all my undercarriage work. They tried to replicate the issue, but couldn't. They cleaned up the front shoes and drums a bit, but said all looked fine.

Yesterday, I drove the F up to Kenosha, WI, to check out the AMC reunion show, and visit with John Begian and his freshly restored '68 AMX. No issues driving the 72 miles up, in the cool morning air. Same issue as last week, however, on the way home. When traffic bottled up on I-294 near O'Hare, the brakes started grabbing, and the engine temp headed higher. I pulled over at the O'Hare Oasis, let the car cool down for 40 minutes, and then drove home with no further issues.

John Begian suggested that I try pulling the vacuum hose off the brake booster, before shutting off the engine, to see if that released the pedal. So this afternoon, I went out cruising again to heat up the car, and got the brakes to grab again, with the smell of brake linings, and engine temp climbing. Brake lights again stayed on when I was out of the car, and the pedal was high and hard. I pulled off the vacuum hose, as John suggested, and heard a whoosh of air, but no change in the high pedal height, and the brake lights still stayed on. The front right hubcap was the hottest, with right rear and left front also pretty warm. Left rear was cool.

Some added background on this car -

  • Master brake cylinder was replaced about 2 1/2 years ago.
  • Hydraulic brake light switch was replaced less than a month ago, when up at the Iola, WI car show.
  • Rear brake shoes were replaced this past winter, along with new used brake drums sourced from a fellow Club member.
  • Front brake shoes and drums are about 3 years old.
  • Still running DOT3 brake fluid.
  • I've drive the F just over 5,000 miles this driving season, and have never had any brake issues of this type over the 48,000+ miles I've driven this car over the past 10 or so years.

I'm thinking it's the brake booster causing these issues, but not sure. My mechanical knowledge is weak, at best!

I welcome your thoughts!

Noel Hastalis

Burr Ridge, IL

F coupe


Posted by: John Grady <jkg@xxxxxxxxxxxxxxxxx>

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