WD45 Diesel Oil Pressure

[JD-Matt]

Having low oil pressure issues in a WD-45
diesel. It will read toward the low side of
normal cold, then steadily drops completely
off after the oil warms up, say after the
first 10-15 minutes. I'm running 15-40 oil.
I've tried a new and correctly calibrated
gauge, checked the filter stems and it has
the correct filters. Engine doesn't seem to
knock or make any noises like the bearings
should be that bad. I find quite a bit of
info about oil pressure issues on a gas
engine but none on a diesel. Any thoughts
where to look next?

 

[funky_g00]

First verify your actual pressure. I do not know what it should be on a diesel but on a gas 7 to 12 psi is about all you will have when warmed up. Since you mentioned stems make sure the filters are cotton packed and not paper. I am guessing they are correct since you have some kind of initial pressure. From there I would say your cam bearings have too much wear.

 

[DrAllis]

(quoted from post at 04:25:48 08/21/23) Having low oil pressure issues in a WD-45
diesel. *** Get a 50 psi gauge. Oil pressure range at wide open throttle should be 25 to 40 psi. I'd expect 30 to 35 psi when HOT. Hot slow idle should be more than 10 psi and 15 would suit me fine. May want to check pressure at the filter base and at the main oil galley on the left side of the engine block to compare the differences.

 

[JD-Matt]

I hooked my 60 psi gauge to the base on the
front oil filter last night. With the oil
warm enough for the dash gauge to drop off
completely, I have a consistent 9-10 psi at
the filter base at fast idle. Slow idle it
drops to 2.5-3 psi and the needle bounces
around quite a bit. Haven't checked at the
main block port yet, ran out of time. Any
suggestions where to head next? Oil pump
relief valve spring maybe? Or bearings?
Engine doesn't knock at all, so I have a
tough time thinking bearings are worn
enough to cause that low of oil pressure.
I'm going to pull the valve cover tonight
and make sure that everything is as it
should be in there. Thanks for the feedback
so far.

 

[Traditional Farmer]

There is a screw up on the side at the front of the motor to adjust oil pressure,has a lock nut on it, the lock nut may have come loose and the screw backed out.If not turn the screw in to raise the oil pressure.

 

[BonaparteSouth]

Dr do you think it could be starving at pickup or pump??

 

[J. Schwiebert]

How much oil is flowing to the rocker arms? On a Buda in a cockshutt we would pinch the oil amount back if there was a large amount

 

[DrAllis]

Whatever the oil pressure is when cold at full throttle is what the pressure regulator is set at. So, what was it ?? 35 psi ?? 40 psi ?? I had a friend who aquired a freshly OHauled D-19 (same engine family) that had OK oil pressure when cold but fell way off when warmed up. He tried a different oil pump and tried adjusting the pressure regulator with no improvement. I told him he knew how to drop the pan, start plasti-gauging the mains and rods. Well, it had -.010" mains on a crank that was ground -.020". It didn't knock either. My bet is loose cam bearings or mains and rod bearings.

 

[JD-Matt]

10-12 psi is the absolute best I can get
out of it, cold at wide open throttle. From
your last reply it makes me think pressure
regulator then possibly. Next question, if
it is the regulator, do all 45 diesels have
an externally adjustable relief valve or
are some of them a fixed pressure and only
accessible by dropping the pan and oil
pump? I can't seem to find the screw on
this engine, and from the looks of the agco
online parts book they show 2 different
styles, one external one internal but make
no mention of an engine serial number break
or anything.

 

[JD-Matt]

So edit on the relief valve, I found it hiding clear up under the injection pump once I got the right light and got down on a creeper. Took it out and things look good. I'm beginning to think maybe the best thing will be to drop the pan and see how clean the oil sump is, and plastigauge the bearings while I'm at it. Allis diesels are all new to me so I'm learning as I go.

 

[DrAllis]

Plastigauge in-chassis is a challenge for main bearings. Technically, there should be zero oil film on each of the bearing shells and the crankshaft journal. Everything DRY. Then, there is the matter of the weight of the crankshaft smashing the plastigauge. Rod bearings much easier. Good luck.