Cub oil pressure

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Ray wood
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Cub oil pressure

Postby Ray wood » Tue Sep 21, 2021 9:35 pm

I just noticed that my 1953 Cub's oil pressure gauge has been reading zero. I looked at this thread and tried to prime the pump using the hole in the back of the oil filter housing. I filled it to overflowing several times. Every time I start the engine the oil pressure gauge starts in the red zone and over about 30 seconds drops to reading zero. Any suggestions appreciated.
Ray (in New Zealand)

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Glen
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Re: Cub oil pressure

Postby Glen » Wed Sep 22, 2021 1:00 am

Hi,
Welcome to the website.

You didn't say, but I guess you checked the oil, and it is above add, on the dipstick.

If you are using thin motor oil, it might be too thin for the engine. Some Cub engines are worn, and the oil pressure is somewhat low. The oil pressure can get lower in hot weather too, you probably know.

Some of the people on here use 15W-40 motor oil in their Cubs. It is thicker than thin oils.

The oil gauge may not be working right. People on here have tested them with air pressure.
You could remove the gauge, and use different pressures of compressed air, I think they use a blow gun for the test.
The gauge with red and white areas I think is a 40 lb maximum gauge.
Remember if you have a long air hose, the air pressure can be less than the gauge on the tank shows, by the time the air gets to the end of the hose.
Use your safety goggles when using the air.

I don't know how hot it is there, I guess it is the beginning of Spring there. :)

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Re: Cub oil pressure

Postby outdoors4evr » Wed Sep 22, 2021 5:10 am

Sounds like the pump isn't picking up new oil from the oil pan.
(speculation ahead) Perhaps the oil pick-up tube has fallen off and is laying in the bottom of the oil pan?
Other options may be the oil pressure regulator spring has broken and the oil is just bypassing back to the pan.
This is a really long shot (and I would not check this first), but maybe the oil pump has failed or is no longer turning?
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Eugene
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Re: Cub oil pressure

Postby Eugene » Wed Sep 22, 2021 5:49 am

Welcome.

What is the history on the engine? A recent engine overhaul? Last engine overhaul?

Thinking. Engine stopped, oil pressure zero. Start engine, oil pressure comes up into the red zone on the oil pressure gauge, then oil pump is working, building up oil pressure.

Then the gauge drops back to zero. Test gauge. That's the easy check.

Next thought. Rod and main bearings clearance issue.
I have an excuse. CRS.

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Re: Cub oil pressure

Postby Matt Kirsch » Wed Sep 22, 2021 10:37 am

Frankly I'm not sure there is an oil thin enough that it would pump through the system without generating any oil pressure.

Also in my experience "thicker" oil makes no difference whatsoever. Even 20W50 doesn't help.

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Re: Cub oil pressure

Postby Clemsonfor » Wed Sep 22, 2021 5:17 pm

Is this a new issue? Is this tractor new to you so you don't know it's history or what it was doing a few months ago? Some back info would help a little more here.

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Re: Cub oil pressure

Postby Glen » Wed Sep 22, 2021 7:30 pm

Matt Kirsch wrote:Also in my experience "thicker" oil makes no difference whatsoever. Even 20W50 doesn't help.


I've seen it said on here before that thicker engine oil helped the oil pressure.
I don't think anyone disagreed with it being said then.

Ray wood, also the oil intake screen in the oil pan could be somewhat plugged.
Some Cub engines have sludge in the oil pan from years of use, and possibly few oil changes.
Below are pics from TM Tractor of the screen.

http://www.tmtractor.com/tm-tractor/gen ... en_001.htm

If you remove the oil pan, there are 3 bolts across the rear of the pan. They thread into the rear seal retainer. The retainer is made from soft metal, don't tighten the bolts too tight, the threads can strip.
You may need a new oil pan gasket if you remove the pan.

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Re: Cub oil pressure

Postby Ray wood » Wed Sep 22, 2021 10:04 pm

Thanks for the ideas. I replaced the valves a few months ago and was so pleased (surprised?) when it ran again that I didn't pay attention to the oil gauge. I took off the oil pan to replace the leaking gasket when I did the other work but didn't do anything else under the engine. I'm using 15-40 oil The dipstick shows sufficient oil in the engine. I didn't use the tractor much over winter and only noticed the oil pressure problem a few days ago. Checking the gauge sounds like the easiest thing to try first.

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Re: Cub oil pressure

Postby Pap » Thu Sep 23, 2021 8:23 am

Welcome to the forum Ray and good luck with your project.
Are We Having Fun Yet ? :D
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Mike in Louisiana
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Re: Cub oil pressure

Postby Mike in Louisiana » Thu Sep 23, 2021 11:06 am

Yes check for bad gauge first.
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Re: Cub oil pressure

Postby Matt Kirsch » Thu Sep 23, 2021 11:39 am

Glen wrote:
Matt Kirsch wrote:Also in my experience "thicker" oil makes no difference whatsoever. Even 20W50 doesn't help.


I've seen it said on here before that thicker engine oil helped the oil pressure.
I don't think anyone disagreed with it being said then.


If you can link me to that thread I will be glad to go back and disagree with it, LOL.

Seriously, though, at one time in my history I had a Cub Loboy that the oil pressure got pretty low on after being worked for an hour or so. It would start around 35 and be down around 12 when I finished mowing. I had heard the "thicker oil" advice and went to straight 40. No change. I could not find straight 50 so I went to 20W50. Again, no change. Not even 1PSI.

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Re: Cub oil pressure

Postby JohnMihevic » Thu Sep 23, 2021 2:29 pm

What is the normal length of time for oil pressure to build on the gauge? If I am using the Cub, and I shut it off and let it sit an hour or so, the oil pressure will come right up when the engine starts. However, if it sits just one day and I start the engine, it takes about 15-20 sec to build pressure. This seems a little long to me. I would rather not prime the oil pump after just a day or two. Does the oil drain back out of the oil filter housing if the tractor sits for a day or two?

John M.

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Re: Cub oil pressure

Postby Eugene » Thu Sep 23, 2021 3:34 pm

JohnMihevic wrote: Does the oil drain back out of the oil filter housing if the tractor sits for a day or two?
Yes. The time frames you reported in the previous post are normal.
I have an excuse. CRS.

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Re: Cub oil pressure

Postby JohnMihevic » Thu Sep 23, 2021 5:19 pm

Thanks for the reply. I feel better now, that it's normal. I'm thinking--c'mon, c'mon--those bearings are dry during those 15 sec.

John M.

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Re: Cub oil pressure

Postby Eugene » Thu Sep 23, 2021 6:11 pm

JohnMihevic wrote:I'm thinking--c'mon, c'mon--those bearings are dry during those 15 sec.
Oil remains in the bearings after engine is stopped and they are not dry. Oil is being pumped immediately upon engine start up, reaching the bearings, and flowing into/filling the oil filter housing.
I have an excuse. CRS.


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