power assist brakes - reply

[John Hertog <crossram@xxxx>]

Received reply from William Barrie re: brake problems. Now we know what
components he worked on - unfortunately, in this case, he worked on all of
them, including the booster !

Bill stated:
>After hooking up the
> vacuum power assist and starting the car, the pedal drops somewhat and the
> brakes lock solid to where the wheels will not turn.

In my opinion, Bill, you "screwed something up" in the brake booster when
you were working on it, or did not reinstall it correctly. . No, the fact
that the vacuum tank is not connected will NOT cause the problem you
describe. Sounds more like the actuating valve in the booster is not
working properly, and like your booster is going into "boost" mode even with
your foot off the brake pedal.

I would disconnect the master cylinder from the firewall and move it aside
(no need to unhook it from the hydraulic line) . Then, start the car and
observe the actuating rod that goes into master. It should not actuate ! If
it does, something is wrong internally in the booster.

Here is a quick synopsis taken from the service manual:

OPERATION:
As the brake pedal is depressed, the trigger are moves back, releasing
sufficient pressure agaist the valve operationg rod, to permit the valve
return spring to close the athmospheric port, and open the vacuum port of
the control valve. As the front chamber of the unit assumes a state of
vacuum, the piston moves forward and applies power to the upper end of the
power lever. Power is then transmitted to the master cylinder thru the
reactionary linkage and the master cylinder pushrod.

Hope this helps.

John Hertog
Sag Harbor NY

----- Original Message -----
From: "William Barrie" <blueweststudio@xxxx>
To: "John Hertog" <crossram@xxxx>
Sent: Thursday, November 27, 2003 11:50 AM
Subject: Re: [Chrysler300] power assist brakes - reply


Happy Thanksgiving John,

Thankyou for the delux express reply. I did rebuild all the wheel
cylinders, replaced all the brake lines as well as rebuild the master
cylinder. I cleaned and inspected the booster unit which looked to be in "
like new" condition. I think I may have discovered my problem. In my
excitement to drive the car, I did not get around to installing the vacuum
reserve tank, ( duh ) and simply connected the hose from the intake to the
booster unit, so that the manifold vacuum was sucking the brake pedel to the
floor. Does this sound like the possible problem to you?

Barrie Oblinger
Mebane, North
Carolina

> John Hertog <crossram@xxxx> wrote:
> Hey Bill,
>
> It would sure help to know what components were rebuilt or replaced. All
it
> says is that you rebuilt the "brake system". Did you rebuild or replace
the
> master cylinder? What about the brake booster - was it also rebuilt or
> worked on? Or, did you just do work on the four wheels ? Were brake
hoses
> replaced?
>
> Please elaborate and give accurate description of exactly what work was
> done. We can't really adequately help diagnose without more info as to
> which components were worked on, and which were not.
>
> Happy Thanksgiving to All
>
> John Hertog
> Sag Harbor NY
>
> ----- Original Message -----
> From: "William Barrie" <blueweststudio@xxxx>
>
>
> After rebuilding the brake system on my G, I adjusted them to
> where I have good pedal and good stopping power. After hooking up the
> vacuum power assist and starting the car, the pedal drops somewhat and the
> brakes lock solid to where the wheels will not turn. I then backed out
the
> adjustable nut on the master cylinder to the point where the wheels would
> turn but then the pedal would go almost to the floor before stopping the
> car. Also when I turn off the engine, the pedal comes up fully.
>
> Any idea of what's going on?
>
> Barrie
>

>