[Ethanissan]

Hey all,
Does anyone know what the oil pressure should be on the SD33T at idle? Normally mine sits at 19-20 psi, and if I’ve been for a long highway drive it’ll get down to 15-16 psi, which seems way too low to me. From what I know about other engines it should be around 25 psi at idle, so I’m wondering as well if my JRP gauge could be inaccurate.
This is using Castrol RX-Super 15w40
Thanks


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[dkril]

Could be an inaccurate gauge. The lower-pressure-after-a-long-cruise bit may be a sticky oil pressure relief valve.

 

[patroladdict]

Sounds right, hot oil will be thinner and result in lower pressure.

 

[Ethanissan]

The lower oil pressure after a cruise is definitely due to the oil being warmer and thinner, there was one time after a very long sand drive on Fraser where the pressure was at 8psi at idle, which I know for sure is too low. It increases with revs up to just above 40psi, but I’m wondering if my oil pump is on the way out and can’t pressurise enough oil at low RPM’s. Main reason I ask is because there’s a TD42 high-flow oil pump for sale and I’m wondering if it would bolt up to the SD.
I know the injector pump could be bolted up because there’s someone who’s running an inline SD pump on their TD, so evidently there’s similarity between the engines, which makes sense. They’re both old style pushrod IDI diesels made by Nissan in the same era of engine design, and the TD line was basically made to replace the SD line. So I’m curious whether the oil pump assemblies are interchangeable between the 2 motors.


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[james008]

Do you have another gauge to verify against?
From memory 8psi is pretty close to when the EDIC will shut the engine down.

A few other engines also used the old Diesel Kiki inline pump in the 70s-early 90s. As for oil pump, from memory TD is different but I wouldn't jump straight to oil pump. SD rods are offset which can accelerate wear, mains could be worn, piston oil squirters worked loose, oil pressure relief valve issue etc etc.

 

[rgren2]

Different engine, but mine runs 7-9 psi on idle when warm, has done so since new and is quite normal for the motor. I was concerned until I had it confirmed.