Marshall, Joe, et al:
Thanks for the quick replies. I figured the sending unit would be the place to
attach a manual gauge, but I thought there would be a procedure in the
FSM with
more specs than the awfully vague TDM numbers. If my car would barely
hit 3 bar
by 3k, I'd say the motor would be junk in short order. My car idles at
1.75-2.0
hot and pegs almost anywhere off idle.
Symptoms were 0.5 bar indicated at idle, then increasing to 3bar as you drove
off, but then dropping to zero! My BIL had it checked out today, and
got lucky.
First it was just a bad sending unit (whew!) and second the local parts place
(dealer?) had a new one on the shelf. It's already fixed and back on the road!
I was surprised myself at the quick TAT, since he just called me this
AM asking
how to diagnose it. I was about to have them pull the filter and check
the stuff
Marshall mentioned. This car gets M-1 or D-1, btw.
:-)
Thanks again,
Dave M.
------------------------------
Date: Tue, 28 Jun 2005 08:10:20 -0700
From: Joe Knight <[EMAIL PROTECTED]>
Subject: Re: [MBZ] OM603 oil pressure question
18.4-1101a indicates the pressure sensor is at the base of the filter
housing; that'd seem to be an appropriate place if you want to hook up
a test gauge. TDM indicates that pressure may drop to .3bar at idle
and should be at least 3bar at 3Krpm. 18.1-1101a deals w/ the oil
pressure relief valve on the pump and indicates that control cuts in
at 5.8bar. I'm wisless at the moment but it might just be worth a
peek. Symptoms?
j
------------------------------
Date: Tue, 28 Jun 2005 11:18:34 -0400
From: Marshall Booth <[EMAIL PROTECTED]>
Subject: Re: [MBZ] OM603 oil pressure question
There are NO published specs I've ever seen beyond the "must be greater
than 0.3 bar at idle and at least 3 bar at 3000 rpm." Those numbers are
low (but safe). The most common failing is the is of the "O" rings on
the stem. They will result in low idle pressures (but usually still
above the min) and some lifter clatter. If the grommet inside the oil
filter is disp[laced when the filter is installed, pressure will read
even lower than if the "O" rings are bad. Most (75+%) of the pressure
problems I've seen reported are caused by one of those being the
problems. If the relief valves (they open in the 5-6 bar range) fail
open, pressure will not peg when it should at engine speeds in the
2500-3000 rpm range. There's one in the filter housing (but I've never
hear of it failing) and one at the oil pump (I know of half a dozen or
more of them failing - all on older OM61x or OM621 engines). Finally the
pump CAN fail and then usually both hot idle pressure AND mid rang rmp
pressure are both low or nil.
Marshall
