L295DT low oil pressure, and cam plugs are in.

[dpfaff]

I recently bought a Kubota L295DT that has low oil pressure. At operating temperature it has about 5 pounds of pressure at idle, and at 2800 rpm it has about 15 to 20 pounds of pressure. The manual says at idle it should have no less than 14 pounds and at rated speed it should have between 43 and 60. I've been doing a lot of reading on these early tractors and everything I've found says that it's most likely because the oil plugs in the cam blew out. Well, after reading this, I took the front cover off of the engine and found that the front oil plug in the cam had already been repaired. I therefore decided to pull the cam and check the back plug. That plug is also still in the cam. I then pulled the oil pan and found nothing there except for the original front cam plug that someone had already replaced. I pulled the sump and the seal there looked fine. I pulled the oil pump and everything looks good there, too. I checked the oil relief valves thinking that something was preventing the balls from closing all the way, but once again, nothing there. I don't know where to go from here. The tractor only has 900 hours on it. Any help would be greatly appreciated!

Thanks!

 

[rbargeron]

Its possible the cam plugs were originally repaired after running with little or no oil pressure and there is some permanent wear. Its also possible it will run a long time even with reduced pressure.

One thing you could try would be some 20w50 or straight 40w or 50w racing oil to see if pressures improve. Get a good quality name brand like Valvoline or Castrol. If it's better stay with it - but change oil and filter more often.

How was the oil pump inspected? Sometimes it's hard to tell if a gear pump has too much internal leakage. There's a used one here that might be useful to compare.

The recommended oil pressures are nice to have, but even 5 psi is enough to lubricate the bearings. Does the oil light come on at idle?

Some engines with excess main bearing wear will show fluctuating oil pressure as the load reverses (pulling/coasting) - the crank migrates in the clearance affecting oil port flow resistance. Something to look at after its back together. Good luck, Dick B

 

[dpfaff]

Thanks for your response. Yes, the light comes on while the tractor is idling, but I have a gauge hooked up as well so I may simply unhook the electrical oil sending unit. I took the oil pump apart and used a feeler gauge to check clearances, and everything was fine. The cam journals were also perfectly within tolerances. There seems to be no wear on this engine, so that's why it makes no sense to me that I'm losing pressure. When running, the engine sounds tight. No clattering or knocking whatsoever. I can't help but wonder if there is another plug missing somewhere internally. I've been trying to find the schematics for the oil passages in the block, but I haven't been able to find any yet. My next step is to blow air into the passages and see where they all lead. After that, if nothing turns up, I'll take your advice on the oil. I was running 30 weight in it.

Dan

 

[lugbolt]

Look on the outside of the block for any missing plugs. On some of the bigger "L" tractors (and a few "M"s), have seen external plugs fall out causing low oil pressure-or in a lot of cases destroyed engines. The ones I seen were always passages that were drilled from the outside in and the exterior passages were just plugged, most of them were on the suction side of the pump's plumbing. AND...most of the ones I've seen were also behind the front frame, necessitating removal of the entire front frame assembly, leaving the engine hanging on the transmission to gain access.