'51 Cub Service & Rewiring & Alternator

[Eugene]

Dale, did you clean out and examine the bore that the oil pressure valve is in? Is it possible that there is contamination in the bore that is sticking the valve?

My thought also.

Edit. Still thinking on this problem.

I bought this tractor a year ago, and it had good oil pressure, and easily ran a Woods 59.

How long did you mow with the Cub? 20 - 30 minutes and it still held good oil pressure?

If cleaning up the P regulator bore and new valve doesn't work - - pull the main and rod bearings.

[Dale Finch]

I did clean it out, and oiled it generously. I am about to go out and remove it again, double check the bore, and install the one that came with my Cub Kit. Will update later.

Oh, and I will double-check at the filter housing AND the pressure gauge port for oil flow.

[Dale Finch]

I swapped out the spring and valve, with the same results.

How long did you mow with the Cub? 20 - 30 minutes and it still held good oil pressure?

If cleaning up the P regulator bore and new valve doesn't work - - pull the main and rod bearings.

I would mow for several hours a day for several days... approximately 8 acres of pasture. To be honest, I think the pressure did drop a fair amount, but I know it started off OK. Never had zero on start-up until now...& I'm pretty good at checking each of my cubs when starting, plus periodic checks while using.

Checking oil pump operation:
https://youtu.be/TRBlAjWP7qY

And checking flow to gauge:
https://youtu.be/TRBlAjWP7qY

If I have "flow" as seen in the videos, could the problem be a worn oil pump not putting out ENOUGH pressure, or do you think it's now isolated to the engine, itself? Sure would prefer the former, rather than looking at an engine tear-down...

[Eugene]

Oil pump is working. Oil pump is almost a full tear down or a might as well while you are there.

Easier to plastigage the rod and main beaings. I think that is were you will find the problem.

[Dale Finch]

OK. Venturing into new territory, but I do have some plastigage...somewhere!
I must say, though, I HATE working under a tractor, having to hold my arms up. Even worse is the Woods 59 is under this tractor...sigh...

But I can't think of any other direction.

Quick question sort of asked above...can the pump be pumping without the proper pressure? Guess it wouldn't show zero though...hmm...just thinking out loud. (Dangerous!)

[Eugene]

Quick question sort of asked above...can the pump be pumping without the proper pressure?

Yes. Restrictions in the oil flow cause/increase oil pressure. Less restrictions, lower oil pressure.

My opinion/thought. I would pull the engine and put it on the engine stand. You will be disassembling a fair part of the engine while investigating the problem. Might as well do a rebuild.

[Jim Becker]

Since the engine was running reasonably well and had good oil pressure until it abruptly didn't have good oil pressure, the problem is likely to be the result of some one thing happening. It makes more sense to find the one thing and fix it rather than rebuilding the whole engine. A compete rebuild is just throwing parts at it.

I think my next step would be to pull the valve cover and see if one of the plugs fell out. Next, I'd pull the pan and do a visual inspection from there. If still nothing found, I'd probably pull the oil filter, fill the filter housing with oil, and look for it to come out. As much flow as you had in the video, it should show up somewhere. If not, I might put a few pounds of air pressure in the gauge hole to see if anything happens.

If all this fails to find anything, I'd probably split the tractor and pull the oil pump to see if the drive key has sheared.