Oil Pressure "gauge" reads low when warmed up... - Diesel Forum - TheDieselStop.com
'99 & up 7.3L Power Stroke Engine and Drivetrain Discussion of the '99 & up 7.3L Power Stroke diesel engine and drivetrain in the 1999-Up Super Duty trucks and Excursions. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 7.3L Power Stroke engine.

 
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post #1 of 4 (permalink) Old 07-18-2019, 01:55 PM Thread Starter
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Question Oil Pressure "gauge" reads low when warmed up...

2002 F-250 with 330k, starts and runs great, but after the engine warms up (200° indicated coolant temp) the oil dash gauge drops from the normal range to L and the "check gauge" idiot light comes on. Engine continues to run smooth as silk and has good power despite this disconcerting indication. It seems odd that it would be the sensor, as it works fine until engine temp comes up. Oil fill (Amsoil 15W-40 Marine) is normal level and has less than 300 miles on it, no sign of foaming or other oil specific issues. HPOP has less than 3000 miles on it, has all new lines and there's no oil in the valley. LPOP is a possibility due to age/mileage but I would expect the HPOP to starve and the engine to have rough idle or just stop running. The other consideration is piston cooling jet failure, but I would expect oil foaming from that.

I know I'm missing something, suggestions appreciated.

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post #2 of 4 (permalink) Old 07-18-2019, 06:00 PM
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I would suggest putting a mechanical gauge on it to get an accurate pressure. It might be time to replace the oil pump. That’s an easy task. The sender could be biased. If you do replace it, get a Motorcraft sensor. The auto parts varieties don’t seem to work on our trucks.


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post #3 of 4 (permalink) Old 07-19-2019, 12:00 AM
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It is not uncommon for your oil pressure to be less than 12 psi at idle when at it is at full temp.

The sensor is in the hpop reservoir and is the first to see low pressure. As RT stated, the sensor is most like bad. It's an easy change too. You can read the output from the sensor to get an idea.

A LPOP may also be in your future as long as you verify the rest of the low pressure oil system is healthy.

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post #4 of 4 (permalink) Old 07-20-2019, 09:37 AM
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Also if you want to test your LPOP pressure, when you change the sensor on the HPOP reservoir you can put a mechanical gauge in that spot first to test pressure. Fits right in no special fitting needed. Run a test then put your sensor in.

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