Re: [Healeys] Brake Servo Operation

[Larry Wendland <bighealey3k@aim.com>]

When you apply the brake a small gulp of air is momentarily introduced to the 
intake manifold from the brake booster in an effort to replenish the vacuum in 
the booster chamber through the large vacuum hose that is between the booster 
and the intake manifold .  The gulp of air momentarily leans the normally rich 
idle mixture out increasing the idle speed.  I am assuming the increase in idle 
returns to normal as long as you keep the pedal depressed and when you release 
the brakes.  Now if the idle stays elevated with the pedal depressed, there 
could be a vacuum leak.  I used to repeatedly depress the brake pedal when 
stopped at a stop light and watch the idle increase and stay increased until I 
stopped depressing the pedal repeatedly and hold the pedal down till it was 
time to continue my journey.  Why did I do that?  To prove to my self that air 
was being introduce to the intake manifold upon brake application.

Larry
'67 BJ8


-----Original Message-----
From: mitch <dayton21@comcast.net>
To: Healeys <Healeys@autox.team.net>
Sent: Fri, Mar 18, 2016 6:57 am
Subject: [Healeys] Brake Servo Operation



Hello,
 
I have the original servo on my 1966 BJ8Â  (Girling MK2A) it was rebuilt by PO 
at some time
I recently noticed  when stopped at a light�.idling ,foot on brake��the 
idle increases by about 300-500 rpm� is this normal?  Also noticed the brake 
peddle is a little lower when applied.   
The car appears to stop â?¦OK
What tests can I do ?
Can I put a new check valve in vacuum line ��without removing the valve on 
the servo?  Or would that cause a problem?
And yes I looked in the archives��.little confusing
Any help would be appreciated
 
Cheers
Mitch
 
Sent from Mail for Windows 10
 

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