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,
Â
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. Â
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
Â
Cheers
Mitch
Â
Sent from Mail for Windows 10
Â
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