I agree with Steve, the column of air in the oil pressure line needs to be
there to dampen out the oil pump pulses. I addressed this issue back on Aug
6th in a reply to the list and David Masucci who had an "oscillating" oil
pressure gauge and he thought air in the line caused it. I related to him and
the list how my '67 BJ8 that I've owned since new and know that the oil line
had never been disconnected from the engine or oil pressure gauge since new
and I was driving in traffic and all of a sudden my oil pressure gauge started
to vibrate and the needle oscillated very rapidly and I noticed a drop of oil
on my left pant leg. I looked at the back of the gauge and saw a drop of oil
hanging on the nut that attached the direct reading oil line to the back of
the gauge. I tightened the nut and it did not help. I guessed there must
have been a column of air in the line that was lost due to the nut at the back
of the gauge not being tight enough. I took the line loose at the engine and
gauge and blew out the line and reconnected both ends and the problem cleared
up and has never reoccurred since and that was back in '69 or '70. There is a
small pin hole in the fitting to the back of the oil pressure gauge that
dampens the pressure entering the gauge and I'm guessing the hole can't dampen
the oil pump pulses with a column of oil directly at the back of the gauge.
The column of air does the dampening and smoothes out the pulses.
Larry
'67 BJ8
-----Original Message-----
From: BJ8 Healeys <sbyers@ec.rr.com>
To: 'Healeys' <healeys@autox.team.net>
Sent: Wed, Sep 29, 2010 11:24 am
Subject: Re: [Healeys] oil pressure relief valve
As far as air in the oil pressure line is concerned, some have the opinion
hat the air needs to be bled out of the line for the gauge to display the
orrect pressure. However, my experience was different.
Shortly after I replaced the flexible oil line on my BJ8, there was a
iscussion on the list about the need to bleed the line. Realizing I had
ot done that and was seeing less pressure than I would expect after a
ebuild, I went out and bled it by starting the engine, then cracking the
ut and letting the oil drip for several minutes into a pan before
e-tightening the nut. When I looked at the gauge, the needle was vibrating
o rapidly that I thought it would break. Then I disconnected the hard line
o the gauge for a minute, then reconnected it. The gauge needle was as
teady as before I bled the line.
y conclusion is that air in the line is necessary to dampen the pressure
ulses from the oil pump and it is not only not necessary but
ounterproductive to bleed it.
Steve Byers
BJ8L/36666
J8 Registry
avelock, NC
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