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I have a 1940 B that has very low oil pressure when I say low I mean the pressure gauge barely moves. the gauge is good and the line from the block to the gauge is NOT clogged and it now has a new oil filter and oil(10w30) in it. any suggestions on what to check next? or do old B`s just have low pressure to begin with?
 

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You may want to swap-in a known good or test gauge to check the pressure. You may have a bad gauge. Another possibility may be a partially plugged pick-up screen. Many of these old tractors have an oil pressure adjustment as well. The oil pump relief valve may be stuck open. Does the oil pressure increase with engine speed?

Check all of the easy items first. Beyond that? Main & rod bearing clearances may be worn and excessive.
 

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Hiya,

SGS makes very good points however, to add my 2 cents, 10w-30 may not be the correct oil for the engine.

The older engines were designed with 30w HD oil in mind as multi-viscosity blends were not available when they were designed. You may want to try a quick oil change to straight 30w HD and see if that resolves the issue before you start looking deeper into things.

I would still put a test gauge on the pressure port just to validate the onboard gauge after the change.

Tom
 

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Hiya,

SGS makes very good points however, to add my 2 cents, 10w-30 may not be the correct oil for the engine.

The older engines were designed with 30w HD oil in mind as multi-viscosity blends were not available when they were designed. You may want to try a quick oil change to straight 30w HD and see if that resolves the issue before you start looking deeper into things.

I would still put a test gauge on the pressure port just to validate the onboard gauge after the change.

Tom
Tom,

That's for sure. Multi-viscosity oils weren't available back then. At operating temp the viscosity of the oils should be comparable. Multi-Vis oils allow for faster cranking and subsequently easier starting.

Another question I should have asked, "Is the oil pressure higher on initial, cold start-up?" If it is then excessive bearing wear is probably indicated.

Some oil trivia...Understanding Multi-Viscosity Oils - The Motor Oil Evaluator
 

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Discussion Starter #5
the oil pressure does go up with the rpms but not much. and the pressure is the same cold and hot. I will dig into it this week and check the things mentioned. thanks.
 

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I have a mt and I ordered a new gauge off ebay and it was made in India.Put it on and it only registered 5- 10 psi.I removed it threw it in the trash and put the old one back on.Those gauges made in India don't work right. I checked the oil pressure with a test gauge and had 35psi. I agree with the other posts check with known good gauge before doing anything else.Thanx,Tim
 

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If you check the operators manual for a 1940 B it will call for 40W oil, higher temps maybe even 50W.

10W-30 is way too thin for that engine.
 

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not sure about the b but my D oil pressure can be adjusted. their is a screw on top of the oil filter housing on the inside of the case not externel. might be something similar on yours. my 8.2l D runs 9-12psi i use 15w40:greentractorride:
 
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