Repair or Junk??

Anonymous Poster · Sep 10, 2001

Well, I am in need of some sage advice, or maybe just some condolences. My old Kubota L175 with more hours that I can try to guess has started showing low oil pressure at very near full RPMs when the engine's warm. It had been showing low, but only at low speed - it steadily (and pretty rapidly here lately) progressed to the point it's at now. Now I know there are some not-too-terrible things that could be causing it, but I assume I'm going to be faced with - at least - main bearings, rod bearings and an oil pump to get any more use out of it. (It runs and starts good and apparently has good compression). Does that sound right? Now the real questions: are parts likely to be available for a bottom-end rebuild? If available, is such a job likely to be more expensive than the tractor's worth? I know there are many unknown factors and much more that can be wrong, but I guess what I'm asking is sort of advice on where to go from here. Advice, or condolences if necessary, appreciated!

scruffy · Sep 10, 2001

Tom, first question, can you do the repairs? If so, then cost would not be all that bad. Are they available? I had no problem getting parts for repairing the tranny on my L175, actually an L1500, but I ignored that. While Kubota may not work on greys (not saying yours is one, but mine was), some NH/Ford, JD dealers and many others do. Mine did everything I wanted it to, and I bought it for 1100, and sold it a year ago w/16 foot trailer for 4grand, depends on the market and right person.

cp1969 · Sep 10, 2001

It may be simpler than that; it might just need a new oil pump.

StanInCalif · Sep 10, 2001

Tom-
I would verify the reading with a mechanical gauge, or replace the sender first. If it starts good cold and oil consumption is reasonable, it doesn't sound real tired. -Stan

smokey · Sep 11, 2001

I would also check that the oil plug in the head has not blown off. Check earlier posts on this known problem.

Anonymous Poster · Sep 11, 2001

Check oil pressure with master gauge. If it is very low, it normally bypasses large amounts of oil. The camshaft has a metal plug in the centre that has been known to fall out.....allowing heaps of oil to drain out of the oil gallery.

This involves removing the timing case,and is usually a job for a mechanic. We repair them by fitting a new plug and fixing in place with a small spot weld.

It is very unusual for an engine to suddenly loose a large portion of its oil pressure simply with wear and tear of bearings
etc. Its always worth checking this plug as the repair is easy and relatively inexpensive. And you may get years more good service from your Kubota !!

scruffy · Sep 11, 2001

If the engine loses oil pressure as it warms up, to me that is indicative of worn bearings. the oil viscosity is lighter as the oil warms, thereby blowing by the possible play in the rod and main bearings as well as the cam bearings...but then I am basing my thought on the ol' gas mechanic days, not diesels

rbargeron · Sep 12, 2001

Tom - in your original post you're instinct was right to question whether bad bearings were consistent with good compression and good starting. Kubota engines have very rugged bottoms - odds are that the low-oil-pressure problem is due to something else.

One way to look at it is that tractor engines with 1000 hours on them are roughly equivalent to car engines with 50,000 miles - not expected to be worn out. If your engine has 6,000 hours, you'd be getting into the normal life of a little VW diesel - and the Kubota is a much stronger unit than that.

Anonymous Poster · Sep 13, 2001

That true, when the bearings wear, oil pressure is reduced.
The key question is : what is the oil pressure when it is hot and running at speed?

with the plug missing from the camshaft we measured about
6 psi. Normally an engine would have to have very worn bearings before oil pressure is this low.

From what Tom said I thought the low oil pressure was evident
from the oil light.The L175 normally does'nt have an oil gauge.
For the oil light to be on at speed, the oil pressure must be real low.

The important thing is the check the pressure with a gauge that's known to be good.Then decide on repair procedure.

We have seen several units with this plug missing and some of them have been working for something like 2 years before
it was repaired. Quite amazing really.

Anonymous Poster · Sep 13, 2001

The oil pressure light is off at full throttle, but comes on when the engine speed decreases even slightly - as when going even slightly uphill with bush hog engaged. This happens only after the engine's well warmed up. I have replaced the sender, and according to the manual the pressure light comes on at 22.1psi. So, it appears I have just slightly over that at full throttle with a warm engine, and less at anything less than full rpms. I assume that if it were the plug problem, I'd have less oil pressure than that?

From the above, I'm beginning to think that, after verifying the pressure with a gauge, best bet might be to start with a new oil pump. Make sense?

Thanks for the posts.