BJ42 3B oil pressure and temps

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Apr 14, 2003
Fairfax, VA
I picked up a '81 bj42 with a 3B diesel and am a little concerned about the oil pressure. I have an aftermarket oil pressure gauge which I feel is accurate and the pressure looks fine running down the road but drops while idling. Is this typical? What kind of numbers should I be looking for.
(using 15w-40 oil and in warm weather).

Also what kind of coolant temps should I expect?

oil pressure : factory spec is 4.3 psi min @i idle and 36 to 85 psi @3000rpm at operating temp.

coolant should be between 80 and 90°C (176-194F)(2nd mark from the left on the factory gauge) for temperate conditions / highway / little load


Denis's figures are good. As to what is normal...???

I have 8lbs hot idle oil pressure, and 35lbs hwy speed oil pressure. That is considerably lower then my cold pressure numbers. Been that way for the last 80,000kms (as long as I have had it). OTOH I know someone that has a 3B with 35lbs hot idle oil pressure and 60ish when high rpm. FWIW I am not worried about mine.

I've a mechanical temp sensor hooked up and I can watch the circut open and close on the gauge, cycling between 190F and 170F (or thereabouts) in normal driving conditions.


Thanks for the numbers Denis and Greg.
I was pretty scared of that low idle oil pressure.
Guess I'm OK


I have two BJ60's with the 3B engine. Typically the oil pressure is higher on startup until it warms up. Once they are warm and idling the oil pressure is right at the bottom on the factory gauge and I've had my '82 since 1989 and have put on about 250,000kM since I got it (330,000kM total). My old Corolla (before I could afford a 'Cruiser) also had an oil pressure gauge and it did the same thing as well. I would not worry at all about low oil pressure readings at idle.
If you are always in warmer climates why not go with a heavier oil, maybe straight 30 weight? The lighter oil is more for flow at cooler temperatures and can be undesireable when it is warmer or hot. It will also increase your oil pressure. Remember that 15W-40 acts like straight 40 weight once it is warm.
You may also be interested to know that these are also well suited to turbocharging and I have just done my '82. It makes it produce much more torque.

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