Re: low oil pressure

Peter A · May 30, 2015

I have a 1952 8N that runs very well. Previous owner did n in frame overhaul.Engine has excellent compression and good power. The only issue with this tractor is the low oil pressure. I have read all the posts, and done all the checks that I possibly could do. I replaced the Rotella 15-40 with sraight 40 wt. I have replaced the gauge with a stewart warner, and I have replaced the oil pressure relief valve and spring. All this has made no difference! 20 to 25 lbs cold and barely above 0 hot at idle. If I raise the idle I can sometimes get it to between 5 to 8 lbs. I'm at a loss....
What about stretching the relief valve spring,or replacing the oil pump gears ?
Any ideas ????
Peter

Tall T · May 30, 2015

Both the 15W40 and the 40 have identical viscosity at engine operating temperature -- the 15W40 just flows easier at startup until warm. For that aspect of your diagnostics i would have gone 20W50 (but not Castrol GTX 20W50, it has poor oxidative stability).

It may come down to plastigage to determine the main and rod bearing clearances to see if they are excessive.

But . . . it may be the pump or pickup tube.

T

TheOldHokie · May 30, 2015

(quoted from post at 11:36:39 05/30/15) I have a 1952 8N that runs very well. Previous owner did n in frame overhaul.Engine has excellent compression and good power. The only issue with this tractor is the low oil pressure. I have read all the posts, and done all the checks that I possibly could do. I replaced the Rotella 15-40 with sraight 40 wt. I have replaced the gauge with a stewart warner, and I have replaced the oil pressure relief valve and spring. All this has made no difference! 20 to 25 lbs cold and barely above 0 hot at idle. If I raise the idle I can sometimes get it to between 5 to 8 lbs. I'm at a loss....
What about stretching the relief valve spring,or replacing the oil pump gears ?
Any ideas ????
Peter

If you are getting 20+ PSI cold the hot drop is not the relief valve - it's oil clearances somewhere. And heavier oils are bandaids that really won't buy you much of an increase or fix the problem.

In frame rebuilds are usually a half fix to buy a little more time. Even if you replace the main and rod bearings you likely still have wider than acceptable oil clearances. The journals do wear along with the bearing shells and the real long term solution is to grind the journals undersize and install the matching undersize bearings. Even just a few thousandths over the new specification means means quicker than normal bearing/journal wear on the "rebuild" and the near term return of reduced oil pressure problems. The only way to really "know" what shaoe the lower end is in is to drop the pan and plastigage ALL of the bearings. If they are reasonably tight then it's time to consider oil pump or other oil clearances.

howdy1960 · May 30, 2015

Had same issue with a 43 2N. Had crank turned when redid engine. Now have 30-35 cold (if 80* is cold) and 20-25 hot at idle.
As TOH said, clearances are too much someplace. Most likely crank and bearings. Drop pan, pull a cap, use plastigage if you don't see worn out bearings and crank. Mine was so bad I didn't waste time with plastigage but cleaned up with a .010 turning.

Peter A · May 30, 2015

Thanks for the comments.I had hoped for a trick that I had missed, but unfortunatly I think that I will be looking at a complete engine rebuild before long. What's that saying ? " in for a penny in for a pound "

cowdog · May 30, 2015

Dont forget to mic the cam shaft and the block were it runs. you can have everyrhing else tighter than a tick and find it bypassing there.. btdt.

Re: low oil pressure

Peter A

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Tall T

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TheOldHokie

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howdy1960

Well-known Member

Peter A

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cowdog

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