1940 Model B oil pressure drop

trhod12 · Oct 30, 2009

I was mowing for approx 3-4 hours last weekend. When I started out the oil pressure was good (approx 15-20psi). When I was finishing up, I noticed the oil pressure was reading about 5psi. The tractor was still purring like a kitten when I shut it down. The oil is full, but is pretty dirty. I have not changed the filter in it recently or anything like that.

Now, in an effort to try and make this something other than the oil pump going bad, is there anything else that might make the oil pressure drop like this????

I remember reading an article (Rod in NH) about how different oil filter media will drastically cause the oil pressure to fluxuate. Is it possible that an oil and filter change will correct this problem, or am I in for a new oil pump????

Thanks in advance for any advice/help you might have on this.

This forum has been EXTREMELY helpful for me, since the tractor is new to me this past summer.

Blessings,
TRHOD12

Jeff Z. · Oct 30, 2009

Pretty normal for that tractor. Try some fresh 10w-30 oil and a Fram C-159 oil filter. Don't worry too much, I have a B that runs 6 lbs all the time. It's been like that for years. Since these are slow turning engines you can get away with it.

Jeff Z. · Oct 30, 2009

PS: Oil pressure will drop when the oil gets hot.
My Jeep engine will idle near 40 with fresh oil.
After the oil get's hot around 30. The same goes for old oil. It won't hold the same pressure as fresh oil.

Dick L · Oct 30, 2009

If you are getting 15 to 20 pounds of oil pressure on start up you are on the high side. To know that means you do not have the correct gage.
5 pounds of oil pressure is not all that bad for that engine with a lot of time on it. It would be a good time to change the oil and filter to have a base line of knowing what oil and filter you are watching. You most likely would not need a (new) oil pump. It might need the pump cover cleaned up some time in the future.

The cover on the right would bypass oil and not give proper pressure or hold a prime.
The cover on the left is how you want it to look before replacing it.

old · Oct 30, 2009

Pretty common with these old Allis engines and as long as you have pressure your probably ok. I run 30W oil in all my tractors to help keep pressure up. I had a WD45 engine in my W Speed patrol for years that when hot had 0 oil pressure and it ran for at least 5 years that way and never gave me any problems. I have since replaced it but when I pulled it out it still ran well but was a little on the weak side

steve(ill) · Oct 30, 2009

i go for the new oil and filter also. i have used 10w 40 oil to help hold up the pressure when motor is warm. either way 10-30 or 10-40 you dont really have a problem if you got over 5 psi. 14-15 psi is normal when cold.

trhod12 · Oct 30, 2009

Thanks for all the responses. You've had me feel better about things.

I'll give the ol' girl some fresh oil and new filter and see how things are.

Anything special about oil/filter change for the B??? Seems like I remember reading about needing to prime the pump or filter or something like that.

Blessings,
TRHOD12

steve(ill) · Oct 31, 2009

motor does not need oil prime unless there is a hole in the suction tube. drain and refill with 10w-30 or 40, and a new FRAM C159 filter. Can also use Baldwin TM300.

trhod12 · Oct 31, 2009

(quoted from post at 19:03:59 10/31/09) motor does not need oil prime unless there is a hole in the suction tube. drain and refill with 10w-30 or 40, and a new FRAM C159 filter. Can also use Baldwin TM300.

thanks Steve

1940 Model B oil pressure drop

trhod12

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Jeff Z.

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Jeff Z.

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Dick L

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old

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steve(ill)

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trhod12

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steve(ill)

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