1961 Int'l B275 Diesel low Oil pressure

Hey folks I am new here and have poked around looking for information but haven't found what I am looking for.
I was using my tractor yesterday and after a while noticed that the oil pressure was low. Normally the guage is at the high end and this was definately not normal. I ran it home and at higher rev's it seemed to pump a bit more. I parked it, checked the oil and it seemed thin from being warm and of course black. I did not notice any milkiness to the oil indicating coolant and I assume that would be easy to spot. Rad seemed to be topped up and the cooling fins were not visible. I am not sure the last time I changed the oil but this tractor does not get steady use so it's not hours and hours of run time. Looking back it seemed to be smoking more than normal under load (brush hog). I have been told a couple of things now, could be the guage, could be the oil pump, could be the bearings, could be head gasket. I was wondering if anyone here had a good place to start and what steps I should take based on probabilites of where the problem may be. I am handy, but not a mechanic by trade so any help is appreciated. Thanks in advance!

now that engine is cooled off check oil, if it seems very thin smell it for diesel, pump seals do go bad and leak fuel into crankcase, thinned oil will not build pressure, will go past rings and be burned but should still indicate over full condition. will leave for the experts input as i'm only a back yard mech with out much experiance.

Interestingly enough, I put a primary fuel pump on it last spring. That was the second since I've had the tractor. I can't imagine that the seal is gone already, but I also didn't think I would need to do it again when I had already changed it out. I will check the oil tonight for sure. Thanks

Hi John, on the BD-144 engine the most common
failure is the diaphragm on the fuel lift pump on
the right side of the engine. This lets Diesel fuel
into the crankcase causing oil dilution. The less
common failure is the oil seal on the drive shaft of
the fuel injection pump.
If either of these parts fail, the crankcase oil
should be thin and smell of Diesel fuel.

JimB

(quoted from post at 03:56:17 11/22/11) Hi John, on the BD-144 engine the most common
failure is the diaphragm on the fuel lift pump on
the right side of the engine. This lets Diesel fuel
into the crankcase causing oil dilution. The less
common failure is the oil seal on the drive shaft of
the fuel injection pump.
If either of these parts fail, the crankcase oil
should be thin and smell of Diesel fuel.

JimB

Click to expand...

Thanks Jim, the oil seems thinned however there is no distinct smell of diesel fuel. If it is the case maybe it's not heavily diluted yet? Is there anyway to check the diaphram? As I mentioned this is a new lift pump and wouldn't have 2 hours running, which doesn't mean it couldn't have been made like that I suppose. The first replacement lift pump only lasted maybe 6 years and this tractor does not see hours and hours of use.
I will see about gettign an oil pressure tester to ensure it's not the guage but I don't expect it's the guage. I have been surprised before though.

Can anyone tell me what the likelihood is of hydraulic oil getting into the crankcase and diluting the engine oil? I was sure I had topped up the hydraulic oil and when I put the bush hog on, the 3pt hitch seemed to be acting as if it was low on fluid, jerking on the lift and the hog isn't that heavy. As I mentioned I don't smell diesel on the dipstick. ADDED - yes the hydraulic oil is way down again so i suspect that is what is going into the crankcase. Has anyone gone through this? I suspect that there is a seal on the pump somewhere but not sure where to start.
Thanks