8N loses oil pressure

[Larry Dean]

My 1949 8N runs great, when started has very strong oil pressure, but loses pressure down to under 10 lbs when it heats up. Any ideas? How intimidated should I be about breaking down the tractor to get to the oil pump?

 

[NOXJohn]

That is normal for an N engine with some reasonable wear on the rod and main bearings. If you have 10 pounds when hot and it stays there you tractor will run many more years before needing a rebuild. I ran my 1949 8n hard for 20 years with around 5 pounds of oil pressure when hot without any ill effects. You may see some improvement by using 10w-40 or 15w-50 oil.

 

[Larry Dean]

Much obliged!

 

[souNdguy]

what oil ya use.

if it holds 10 psi hot idle and is a real thin oil.. just up the grade 1 level and you might be good for a number of years..

6 psi per 1k of rpm is a rough rule of thumb..

 

[Larry Dean]

I've used 10w40 and straight 30 weight. Still drops way down. I'll check the 6 lb at 1K. It may do that, but not much more I'm sure. I have to keep it revved pretty high even when I don't want to.

 

[souNdguy]

15w40 gets used in just about everything here.

in the end.. when you rebuild her.. you will need major work. oil pump.. crank.. maybee even some attention tot he block where the cam runs as there are no bushings or inserts from the factory..e tc.

 

[Larry Dean]

Only thing is, the motor doesn't have many hours on it since being rebuilt. I don't know the rebuilder but got the tractor from a friend who does and he claims he does good work.

 

[Larry Dean]

Also, unless I come up with far more time than I have now, I won't rebuilt her myself. Know a good mechanic near Richmond, VA?

 

[souNdguy]

he didn't do the oil pump then..

 

[Larry Dean]

You're probably right. Thanks again.

 

[TheOldHokie]

(quoted from post at 15:06:13 07/08/13) he didn't do the oil pump then..

Whatever he did he didn't do it right. Knowing only the very limited background info provided my WAG would be excessive journal bearing clearances rather than the oil pump. People botch them all the time.....

TOH

 

[Bruce (VA)]

Yep.

Carl at the NAPA machine shop on Chamberlayne Ave.

Call him at 321-7467
75 Tips

 

[Casey Keele]

Not that I'm an expert here or even close. I changed the oil pressure releif valve and spring on my 9n and it went from 20lbs to 40 lbs and holds.

 

[Den N Ms]

Larry,I would give it an oil and filter change first, with some 20W50weight oil and see what that does before doing a tear down.

 

[Larry Dean]

Thanks! I'll call him if/when I need a tear down.

 

[Larry Dean]

Thanks to all responders. I'm glad I found this helpful site.

 

[souNdguy]

with numbers that go down under 10psi.. he may have just spray painted the engine and said it was rebuilt.

 

[Larry Dean]

Say it ain't so.

 

[souNdguy]

i've seen it. most of us have!

either way. your machine will be awaiting work at some point.

you might get a few more psi with a new oil gauge. stretched spring and 15w40 oil.. or 20w50 in a hot area. don't expect mor ethan a few psi unless your spring is way outta spec.