Oil pressure drops when temp gauge goes up

[RickB2018]

Hi there guys names Rick, I’ve had my 2000 Dodge Ram 2500 for about 4 years now. Since I bought the truck the oil pressure is well above 40 pounds when I first turn truck on. After the truck temp gauge goes up the oil pressure drops below 40 at idle, if I give it some fuel oil pressure goes up. I saw a video of mopar1973man on YouTube explaining that it’s an electronic issue between the two sensors. Is there a fix for this? Thanks for any help in advance

[Mopar1973Man]

No fix. This is normal because of the ECM flash. As ECT is cold temperature the oil pressure will show higher. Then when temperature goes up to operating temperature then it goes down again. But checking my actual oil pressure against the Gauge isn't to far off from actual really.  

[dripley]

Same thing here. Just the way it works.

[AH64ID]

As those guys said it's probably a fake gauge, but with your 2000 it could be correct. Something like a M9173M fast idle kit would let you know if it's real or fake, as the pressure would change depending on the switch position. 

 

Actual pressure will hit 75+ on a cold motor at idle, but warm idle is 18-25 psi. Pressure then comes up very quickly while driving at is 55-60 by 1800 rpms on a warm motor, as you start towing the pressure can drop to 40-50 depending on coolant temp. 

 

Diesel pressure varies quite a bit for such a small rpm window. 

 

If you do have the flash the gauge is useless, even thou it may read close as Michael pointed out. The reason it's useless is that it won't show you an oil pressure problem until it's too late. You could be at 10 psi at 2500 rpms which is well below the required pressure but the gauge would show proper pressure. It's generally not an issue thou, as the oil pumps in these motors are nearly indestructible. 

[notlimah]

5 hours ago, AH64ID said:

Diesel pressure varies quite a bit for such a small rpm window.

 

Why is that? High compression?

[RickB2018]

Thank you guys so much!! I really love this truck I love how reliable it’s been just an issue that I wasn’t sure about. But thanks for the reassurance 

Thank you guys so much!! I really love this truck I love how reliable it’s been just an issue that I wasn’t sure about. But thanks for the reassurance 

[AH64ID]

On 1/21/2018 at 5:36 PM, notlimah said:

 

Why is that? High compression?

 

Just the design of the oil pump and lubrication systems. 

 

On a diesel there is much more pressure on the bearings due to the high torque and low rpms, this demands more oil pressure and thicker oil. The pumps go from idle to max output very quickly. 

 

18 at idle to 60 at 2000 is a huge increase for 1250 rpms of change. 

 

The oil pump also moves 20 GPM at 3000 rpms. 

Edited October 19, 2018 by AH64ID

[SilverMoose]

On 1/21/2018 at 6:18 PM, AH64ID said:

 

 

The oil pump also moves 20 GPM at 3000 rpms. 

Thanks @AH64ID I always wondered what the actual flow volume was.  That is over 13 cycles a minute. That's some oil flow.

 

Not to change the subject but does any one know the flow rate for the 47re?

 

L8tr

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Edited October 19, 2018 by AH64ID