Dennis Perkins wrote:
Marshall,
If my memory is correct most MB diesels idle at about 3 bar (on the
gauge). This equates to 43+ psi. An idling engine really only needs
less than 10 psi to get the oil around at idle. 0.3 bar is about 4 psi
and wouldn't even measure on the gauge. Are you saying that the gauge
can read actually read less than 1 bar and still be in the normal range
at Idle?
Mercedes engine require about 4 psi at idle to provide sufficient
protection. The purpose of the oil pressure gauge is to insure that oil
pressure is sufficient so it is designed to accurately read the range
that must be monitored. So the oil pressure MUST be above ~0.3 bar
(about 1/3rd of the way between the lowest and the next mark) at hot
idle and above 3 bar (the top mark) at 3000 rpm for the engine to be
protected using approved oil. The gauge will read those pressures with
resonable accuracy. Mercedes engines, when started cold will display
more than 3 bar oil pressure but this will drop as the engine
temperature rises. Most engines in good operating condition will display
a hot idle pressure of between 1-2 bar (all of mine do) - that's
"normal," but it can be considerably lower and still be safe. Once the
engine accelerates much above idle, MOST diesels will peg the gauge at 3
bar. While most will reach 3 bar by 1200-1500 rpm there is NO danger as
long as oil pressure rises linearly to 3+ bar by 3000 rpm.
The older Bourdon (direct reading) gauges usually remained pretty
accurate for their life (unless they started to leak). The electric
gauges (introduced in various models during the early/mid '80s)
sometimes read erroneously (often perpetually low or high depending on
what's failed) but usually when they vary, they are working as they should.
Marshall
--
Marshall Booth (who doesn't respond to unsigned questions)
"der Dieseling Doktor" [EMAIL PROTECTED]
'87 300TD 181Kmi,'87 190D 2.5 199Kmi, '84 190D 2.2 227Kmi, '85 190D 2.0
159Kmi, '87 190D 2.5 turbo 234kmi
Diesel Technical Advisor MBCA, member GWSection
http://www.dhc.net/~pmhack/mercedes/mbooth1.htm
