300 D - cause for concern?

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300 D - cause for concern?

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Mercedes >> Mercedes Benz Models >> Diesel Discussions >> 300 D - cause for concern?

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300 D - cause for concern? - 5/22/2008 5:40:29 AM

rhlbenz

Posts: 8
Joined: 11/7/2007
Status: offline

greetings,

i have a 92 300 D 2.5T w/ 205K. quite enjoy the ride but a problem has arisen which i hope someone can give clarity to.

the basic problem is that the oil pressure is very low. with the a/c on, it barely gets above the o mark. without the a/c it hovers between 0 and 1K RPMs.

i was having problems with the ABS light remaining on after starting, and after research replaced the OPV relay, which took care of the ABS problem, but may have affected the oil pressure at idle.

any ideas?

thanks in advance.

Post #: 1

RE: 300 D - cause for concern? - 5/22/2008 5:59:15 AM

rhlbenz

Posts: 8
Joined: 11/7/2007
Status: offline

as an additional note - the oil pressure achieves 3 bars when accelerating or at highway speeds.

(in reply to rhlbenz)

Post #: 2

RE: 300 D - cause for concern? - 5/22/2008 4:38:06 PM

Drrty240D

Posts: 145
Joined: 7/30/2006
Status: offline

Sounds like a real, honest to goodness low oil pressure situation. Only way to know for sure is to attach an external oil pressure gauge to the engine and compare results. Good luck.

(in reply to rhlbenz)

Post #: 3

RE: 300 D - cause for concern? - 5/22/2008 5:06:51 PM

rhlbenz

Posts: 8
Joined: 11/7/2007
Status: offline

interestingly, i didn't notice this problem 'till like i said, began using the a/c, which means the temps have been in the high 80s. today, however, it was in the 60s, and the oil pressure was back up above 1 bar.

how should weather affect this?

thanks again

(in reply to Drrty240D)

Post #: 4

RE: 300 D - cause for concern? - 5/23/2008 4:30:39 AM

Drrty240D

Posts: 145
Joined: 7/30/2006
Status: offline

When the A/C compressor is running with the engine at idle it creates more work for the engine and therefore lowers the oil pressure. It is a combination of the parasitic drain through the belt drive system plus the effect of reducing the RPM by a small amount when the compressor is on. Higher outside temps equate to thinner oil and slightly higher engine operating temps. You'll achieve normal engine operating temp quicker on an 80 degree day versus a 60 degree day.

(in reply to rhlbenz)

Post #: 5

RE: 300 D - cause for concern? - 5/23/2008 2:25:24 PM

lwbrewer

Posts: 93
Joined: 2/17/2008
Status: offline

what weight oil are you running and a manual gauge to double check the electric one 87 300D

(in reply to Drrty240D)

Post #: 6

RE: 300 D - cause for concern? - 5/24/2008 6:07:01 AM

Drrty240D

Posts: 145
Joined: 7/30/2006
Status: offline

I run Delvac or Rotella 15W-40. You can run a higher viscosity oil in an engine that is having internal problems as a temporary measure to increase pressure. Obviously, anything wrong mechanically will need to be fixed sooner rather than later or you risk puking the entire engine. You can try a synthetic 5W-50 like Mobil-1 or 0W-50 Eneos or even an aircraft/motorcycle grade 70W oil.

You'll never find straight 70W in the auto parts store; it will probably need to be ordered online or obtained from a specialty store. Look for Pennzoil, Ultima or Klotz. Your local Harley-Davidson store (?) may have some. Running a heavy straight weight oil is risky due to the high viscosity at startup. If the outside temp in your area is lower than 65 degrees Fahrenheit I wouldn't run the 70W.

I don't have an external oil pressure gauge for diagnostics, but you can buy one at the local auto parts store. Not sure where an external oil pressure connection would be on a 1987 300D - anyone know?

< Message edited by Drrty240D -- 5/24/2008 6:51:58 AM >

(in reply to lwbrewer)

Post #: 7

RE: 300 D - cause for concern? - 5/25/2008 2:55:43 AM

ForcedInduction

Posts: 775
Joined: 5/20/2006
From: Federal Heights, Colorado
Status: offline

The oil pressure sender is electric, check the connection at the pressure sender, ground strap on the engine to the body and connection on the instrument cluster.

_____________________________

1980 240D 3.0VNT 222K Miles. OM617.95, GT2256V VNT turbo, 4-speed manual, 3.46 diff, 15mm rear swaybar, ALDA removed, no EGR and Amsoil by-pass oil filter. Currently 107HP and 195lb/ft of torque at the wheels.

www.youtube.com/Turbo617

(in reply to Drrty240D)

Post #: 8

RE: 300 D - cause for concern? - 5/27/2008 1:07:41 PM

Drrty240D

Posts: 145
Joined: 7/30/2006
Status: offline

So, to check oil pressure using a manual gauge (1) temporarily remove the electric sending unit from the engine (2) thread the gauge (or fitting w/hose to gauge) into engine (3) start engine to check oil pressure.

(in reply to lwbrewer)

Post #: 9