John Deere M low oil pressure

[ndgregor]

1952 John Deere M restoration and can't build oil pressure. I put a new gauge on it, and it runs 5 psi at low idle and 20 psi at high idle. Work done so far: new filter, dropped oil pan and cleaned out strainer on oil pump. Confirmed three washers are on relief valve spring, new oil. Is the next step to look for worn main bearings? And advice please let me know. Thank you.

 

[DJ54]

Oil pressure is built on the cam bushings/bearings first.

What weight oil are you using..?? If not straight 30wt, that might help some.

Years ago on an MT I had, I slipped another washer, making 4, in behind the relief valve, and helped some.

If ever you get a serious oil leak coming from the bell housing, there is a freeze out plug at the end of the camshaft. And if ever you have to replace it, remove the cam shaft, then there is a measurement from the face of the block, to tap the plug in. Go no further, or it will block the oil passage, and you will get no oil to the engine. If you have a service manual, it will give the measurement. It's even in the I&T manuals.

 

[ndgregor]

I have been using 20W, per the service manual. I have tried adding washers on the relief valve, didn't notice a change.

I have not noticed any oil leak similar to what you have described. I did take a rod bearing off, and it is very rough. Planning on plastigage measuring the clearance, but it looks shot to me. My question is at this point can I get away with replacing both rod bearings, and hoping that builds better pressure? Or does the crankshaft need to come out to also hit the main bearings? Are camshaft bearings a concern also?

Thank you,
Nick

 

[DJ54]

If it's worn that bad, I'd say the proper thing to do is remove the crank, have a machine shop check, and grind, with new bearings. Personally, I like to have the shop get the bearings to match the grind. If there is a fit problem, it's on them.

If you're going that far, yes, replace the cam bushings.

Who ever presses the new cam bushings in, do measure the rear one, so as not to block the oil port.

And, if you're torn down that far, maybe a new set of rings. Again, I prefer to use a soft set of rings, such as Hastings. Better to have the rings seat into the cylinder walls, than say hard chrome to cut the cylinder walls.

Might as well do a valve job while your at it. At least check, and lap if that's all they need.

If it's a keeper, spending this much now, will give you many years of service.

 

[ndgregor]

Thank you for the feedback.
How difficult is it to remove the crankshaft? Can you just take off the rod and main bearing caps and drop it out the bottom?