YM165 Low oil pressure

[mutt606]

I have a YM165 tractor with 1050 hours.
The oil pressure idiot light started staying on longer after starting so I finally hooked a gauge to see what it really was.
I have 25 PSI / 60 PSI cold engine (1000 rpm / 2200 rpm)
When up to full temperature I have 5 PSI / 15 PSI

Yeah, not good.

What's my next step? Split the tractor and throw a $180 oil pump at it? Its mowing season and its my only mower!

 

[Roadworthy]

Low oil pressure may be a failing oil pump but they don't usually fail. It could be a weak spring on the oil pressure relief valve. With that number of hours I would not think the bearings could be that worn already.

 

[mutt606]

Are you referring to the springs and such behind the oil filter?

 

[ponytug]

While it is possible that you have an oil pump issue, a bad sender, or bad gauge is perhaps more likely. You can measure the cold resistance of the sender and the hot resistance (wire disconnected), and compare it to what the sender should be. I would measure it, or put a pressure gauge on the oil pressure sender with T before doing too much.

All the best,

Peter

 

[winston1]

60 psi cold tells me relief valve is ok. What weight oil are you using?.

 

[mutt606]

I've tried two senders, one generic Japanese one from the autoparts place, and one from Hoye tractor a few years ago. With the gauge reading 60 psi cold I'd also think the gauge is good. Both senders cause the red light to come on at hot low idle (which corresponds to 5 psi on the gauge).

15w-40, Going to change oil and filter Sunday, have about 50 hours on them. See if that makes a difference.

 

[winston1]

You probably know the book calls for your oil pressure to be 21-35 psi. No doubt doing the easy things first is smart. If oil change makes no difference I think I would try adding a shim in the relief valve even though I doubt it is the culprit. I do know that is a whole lot easier than going into an overhaul or pump replacement. I suppose it is possible the pickup tube could be partially stopped up. Just another possibility.

 

[careyo63]

Should be a screen on the oil pickup tube in the oil pan. Could be dirty. My pan was super nasty and the pickup was dirty. The Hyd. system if it has a filter also is setup the same! The Ym2000 No filter on the Hyd. Sys. just a screen.

 

[mutt606]

Well no luck.

Dropped pan and oil pickup was perfectly clean.
Relief valve was clean. Shimmed it out the thickness of a small nylon washer.
New filter and oil.

Same 5psi @ 1000 rpm, and 15 PSI at 2500 rpm when hot.

Its my only mower, so next step is going to be look for another tractor and maybe make this a winter project, or part it out.

 

[careyo63]

Bearing problem is my guess! Does it look as though a prev. owner may have removed the pan.? Perf. clean a give away!!

 

[5030]

Low oil pressure may be a failing oil pump but they don't usually fail. It could be a weak spring on the oil pressure relief valve. With that number of hours I would not think the bearings could be that worn already.

That would entirely depend on if it was maintained properly and the oil and filters changed in a timely manner. If not, those hours could be indicative of worn bearings or other internal issues.

 

[5030]

Why I NEVER buy a used tractor unless I know exactly how it was maintained. Always a crapshoot if you don't know.

 

[5030]

You might try switching to a straight grade lube oil like say a straight 40 weight instead or even a 50 weight like they use in Harley Davidson's.

 

[careyo63]

I've always ran 20/50. I'm in the south so the summer temps. are very hot. Up N. were it's cooler and cold BT. not really a need for it. All Org. 100 Hr. Oil and filter cahnge for 16Yrs.. Oil use! 1/2 Qrt. 100 tach, Hrs. maybe Walmart brand oil and Fram. Had a problem finding them Yrs ago so Napa filter now. Fram 3593 A NAPA 3262

 

[mutt606]

I've had the tractor for 15 years, my father-in-law had it for 20 before that. It has always been babied, oil changes yearly and kept garaged. Not sure why I have bearing wear.

 

[careyo63]

Pull and check pump then. I already of done it!

 

[etpm]

Since you dropped the pan you could now Plastigage the bearings. If they are within spec. then you would know the problem lies elsewhere.
Eric

 

[careyo63]

The bearings had wear you would see it in the pan! Esp. since you changed the oil you would have seen it in the Dirty oil and in the drain pan. I get all kinds of nasty stuff in the drain pan no metal though. It was real bad the first few oil changes. Whale oil was my guess!! true.

 

[mutt606]

Finally got around to tearing down to inspect.
The big end bearings had 0.003 - 0.0035 of clearance when checked with plastigage. So they fall within spec. There is some light scoring that I can catch with my finger nail.

I pull the engine and finished teardown. The main bearings appear worn. The gold color is not a camera issue, it appears the crank has worn through the silver colored layer of the bearing material.

The bores appear to me (I'm no mechanic) to be ok with some light wear.

Crank looks perfect to me (again, I'm no mechanic).

I'd like some input on how to proceed.

My initial thoughts are:
Gasket set
Hone and new rings
Oil seals
Main and rod bearings
Oil pump
Lap the valves
Do the valve springs need replaced? no idea

Clutch still looks decent, I don't plan on spending money there.
Any other thoughts?

 

[winston1]

I like your train of thought. Personally, I would not replace the valve springs.