The plot thickens on '66 4500 diesel in oil...

Ok. Some may remember that I have a suspicion I am leaking diesel into my crankcase due to rising oil level.

About equal number of members says it could be the seals in the CAV pump, or leaking injectors AS
those who suspect its is hydro fluid leaking in via the power steering pump shaft. (4500 has the gear drive pump)
I changed the oil and filter. Tried black light dye in diesel fuel tank. Inconclusive results. Black light seems to show a little dye but not "smoking gun obvious". Members who suspected leaking pump or injector stated oil pressure would suffer.
So I thought before I remove pump and/or injectors I would test/swap out oil pressure gauge as it looks original and acts suspicious to me, though I am novice to how it should act.
On start up pressure jumps right up to about 70lbs and stays there even at idle. Once warmed up it is just shy of 70lbs and about 65 at idle.
Yesterday I removed the original gauge and replaced it with a test gauge off of a air compressor. Oil pressure acts about the same, maybe 2-3 lbs lower when cold and 2-3 lbs lower when hot. Always above 60lbs.
Test original gauge hooked up to air compressor. It tested fine in 5lb increments from 10 lbs to 70 lbs. Seems if oil was getting diluted with diesel oil pressure would drop.
So, does this lead more towards hydro fluid leaking via worn pump shaft seal?
I am glad to have tested/confirmed my oil pressure is valid.
Too hot to do anything now anyway. Tonite this heat will break hopefully.
Pete

Does the tractor have a manifold preheater? I've had those go bad and leak diesel into the crankcase. Also if it is power steering fluid you're resovoir would be losing fluid. If you pull the dipstick and hold a match to the dipstick it will light if there is some diesel in it. Just my 2 cents worth.

If the damn thing is holding 70 pounds when it's hot then you clearly don't have any fuel in the oil. If it was diluted to any extent the pressure would be more like 15-20 at WOT when it's hot.

Rod

Rod,
Yes, I understand that. What was a doubt in my mind was whether or not the original oil pressure gauge was accurate or not. I have no knowledge of this tractors prior history other then the prior owners sales pitch when he sold it to me. Have found some of what he said was true and some not so true. As expected.
When you start the tractor it jumps right up to 70lbs and stays there. Stays at 70 even at low idle. In my naive experience I was concerned the gauge was inaccurate. Knowing now that is correct I have ruled out my oil "gain" is diesel. That is a relief.
So, as other posters have suggested, time to look at the power steering pump which is supplied by the hydro reservoir on this "66 4500.
Pete

Actually, if you want to get technical... the oil pressure gauge isn't original. Originally, it never had one to begin with.... only an idiot light in the gauge cluster. As far as I'm concerned that's as useful, if not more useful than the gauge.
I'd also say... if you've never seen diesel mixed with engine oil... it's not really something you need wonder about. I had it happen a year ago on a Detroit 3-53 and in two hours it dumped the better part of a tank of fuel into the base. I think we drained off 2-3 buckets on the change. Oil pressure was nil at idle and mabey 20 at full throttle. So if you got fuel in the bottom, you'll know it. Quickly.
PS pumps were very common failures on those tractors. That's the more likely scenario. If you get it before it buggers the pump you may get away with changing the shaft seal. If the bushings are bad, you need a pump.


Rod