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L1500 Low oil pressure

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rtate
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2003-10-10          65982

I was having trouble with low oil pressure on my L1500, so I replaced the oil pump. Mowed with it today and after working it pretty hard the low oil pressure light started coming on again. It seemed to be running pretty hot. What could the problem be if it's not the oil pump? It does seem to run ok for a longer period of time with the new pump, but started coming on anytime the RPM dropped below about 800 RPM.

HELP!


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L1500 Low oil pressure

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kwschumm
Join Date: Feb 2003
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2003-10-10          65984

I'd start by checking the oil pressure sending unit. If it's working OK then a couple of other possibilities could be using an oil of too light a viscosity, or (and this is bad) a worn out engine (bearings, valve guides, etc). ....

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L1500 Low oil pressure

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harvey
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2003-10-11          66002

I'd get a live pressure guadge and put it were the sending unit is mounted. Me thinks before you start replacing stuff you should get a accurate reading of the pressure.

If you have low pressure after running, are return passages partially plugged? Shut down engine and pull dip stick is it low? Does the level come up after a while? This problem is usually caught while oil is cool.

If you have excessive engine wear an oil anaylisis can tell you where the wear is.

As ken asked what kinda oil are you using? Is the engine burning oil? Losing/leaking oil? Does the engine have enough oil?

Did someone swap a dipstick and give you one that is too long, 2-3 quarts will show full while it should have 5-6??? ....

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L1500 Low oil pressure

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Art White
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2003-10-11          66010

What is the low RPM limit supposed to be for that tractor? You could have an engine that is that worn that it would be over heating and causing your problem. The boys gave you some good advice from both Ken and Harvey, a cheap oil would also do what you are refering to. ....

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L1500 Low oil pressure

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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2003-10-11          66018

For more exotic problems, I've heard that a few Kubota engines had an aluminum plug on the ends of the rocker arm shaft. These plugs had a tendency to come out, which would produce low pressure and a lot of oil under the rocker-arm cover. I don't know which engines they were but I heard there was a factory fix for the problem.

Good to make sure the pressure is really low and maybe the engine really is over-heating before doing a bunch of troubleshooting though. ....

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L1500 Low oil pressure

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rhtate
Join Date: Oct 2003
Posts: 4 san marcos tx
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2003-10-11          66046

I Need tohook up a gauge again. I did that before I replaced the oil pump and it would show good pressure until it warmed up, then the pressure would drop.

It was overheating when the pressure really dropped this time. I think I was overworking it in very tall, thick wet grass. I did not relieze it was too hot until I shut it down and i could hear the coolent boiling. I am running Dello 400 10w40 oil. Any othe ideas? ....

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L1500 Low oil pressure

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rhtate
Join Date: Oct 2003
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2003-10-11          66047

Would overheating cause low oil pressure? ....

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L1500 Low oil pressure

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rhtate
Join Date: Oct 2003
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2003-10-11          66048

Would a worn out engine cause low oil pressure with a new oil pump? ....

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L1500 Low oil pressure

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TomG
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2003-10-11          66051

Both over-heating and excessive engine wear can produce low oil pressure. Multi-grade oils thin out above some temperature and excessive bearing clearances or a broken line will reduce pressure. Not an easy thing to sort out because low oil pressure can cause over-heating and so can heavy work on hot days.

If the pressure is OK at first, I'd start by looking for causes of over-heating, but first I'd check the temperature with a thermometer unless the engine makes black smoke or a gauge shows it's over-heating. A bad rad cap can cause the coolant to boil at normal coolant temperatures, but it usually boils over too. Then, I'd start on the list of over-heating causes and there are a bunch. Fan belt tension and clogged rad are easy to check. Water pump, thermostat and hoses are not too bad. Flushing the cooling system and replacing with new 50/50 coolant isn't too difficult. Checking for exhaust obstructions, and engine adjustments is a little more difficult and there are some other things. You might notice if the engine oil level increases and if there are bubble in the coolant. A bad head gasket also can cause over-heating.

At least typical causes of over-heating can be checked out and eliminated as causes in a fairy systematic way and without a huge amount of work. If the pressure starts out low and especially if if it has high hours I'd start by checking out the engine. I'd keep in mind that it's not good to shut down an over-heated engine or to run one that has low oil pressure. ....

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L1500 Low oil pressure

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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2003-10-12          66063

I was too busy figuring an organized way to sort out the problem and forgot to mention an obvious test and I also assumed it's a conventional water-cooled diesel engine.

Looking through the rad cap hole when the engine is at operating temp is a quick check for many coolant system problems. The coolant should be swirling due to the pump flow after the thermostat opens--assuming the tractor has a water pump, thermostat or rad for that matter. It does help to know how normal flow looks though. Some more assumptions on my part are that the the oil filter is right and reasonable new and that the oil pump pressure-relief valve is OK because a new pump was installed.
....

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L1500 Low oil pressure

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rhtate
Join Date: Oct 2003
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2003-10-12          66071

I dont believe it has a water pump, but the radiator cap is bad and needs to be replaced. I didnt relieze overheating would cause the oil pressure to drop. While I was replacing the oil pump, I noticed several spring loaded things that could some sort of pressure regulators. How would i go about checking those out? ....

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L1500 Low oil pressure

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Peters
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2003-10-12          66074

As you heat the oil it will thin and you can get low pressure do to thin oil. Having stated this you need to realise that the overheating will cause oil thinning, low oil pressure and damage to the engine.

The low oil pressure due to the bad pump will generally take out the lower end bearings rather quickly. I recently went through the same scenario on a GM 350. After replacing the pump the pressure dropped once it was up to temp. Better pressure but once the viscosity had dropped the bearings were leaking too much oil. ....

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L1500 Low oil pressure

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TomG
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2003-10-13          66103

A repair manual is needed to check out some of these ideas. You might say how many hours are on the engine. This could be a complex problem and if it's a high hour engine and close to needing a rebuild the easiest solution might be to rebuild it. I also didn't recognize the brand of oil but that doesn't mean much. Some brands retain viscosity at high temperatures better than others. If the oil light doesn't come on initially you might try some light work and see how it goes. If it's a thermo-siphon cooling system (w/o a water pump) the system may be partially obstructed or the tractor just worked beyond it's capacity.

Specific testing of a relief valve (if the pump has one) would be difficult. If the pressure starts out normal then the relief isn't likely the problem (a repair manual should say what's normal). A parts manual would confirm if the assembly is OK. The valve on my Ford looks like an elongated hex head fitting. There isn't an external spring but other pumps may be different. Some engines have internal pressure lines and there are seals on some of these, which are other sources of potential pressure loss. ....

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