Oil Sending Unit Replacement

[Bob E.]

Need to see if I can find the oil sending unit and sensor on my 98D.
I need to replace it as the pressure gauge goes from NORMAL during operation to almost the L when I pull into a rest stop.

I called Cummins and talked with my friend who is the Service Manager in Odessa, Tx and he told me it was probably the sending unit sensor or unit but he doubted that it was the pump itself going bad. The sending unit and sensor is a Freightliner problem it seems and not Cummins.

If I can find it maybe I can replace it myself as it is almost 200 miles to the Freightliner shop.

Anyone done this and is it fesible to do this yourself?
Where is this unit located?

Thanks,
Bob E.
98D, 36T

[AFChap]

Pardon the question if not necessary, but are you familiar with
how a real oil pressure gauge operates?? Most vehicles today have constant on/constant off sensors rather than sensors that read true pressure. True oil pressure on a big diesel will be very low at idle, and in normal range at high idle and above. ...which is exactly why you should not idle a big diesel for extended periods unless the engine is at "high idle" of 1000 rpm or so. I would much rather have a real oil gauge than tha "idiot" gauges most vehicles have as all an idiot gauge will do is tell you why you expensive engine is toast ...it will not alert you to dropping pressure in time to avoid extensive damage.

[Bob E.]

Thanks for your answer. I do know how an oil pump is supposed to work but this is my first diesel and you answered my question.

Instead of just letting it idle at the rest stop, I need to put it on fast idle if I let it run. I did not know that and no one mentioned this to me.

That means to me at least that there is nothing wrong with my unit as it is doing what it is supposed to do. It stays inthe NORMAL range when driving and at high idle and only drops to almost the L when stopping at red lights, etc.

I will get it checked by Freightliner computer the next time I am up near Lubbock (200+)miles.

Thanks again.

Bob E.