what is normal oil pressure ?

[Danbo56]

What is the normal operating oil pressure for a Mf50 with a continental gas engine?
I put new gauges in... including the oil pressure gauge but now I'm noticing that the oil pressure never exceeds 20 . I don't remember it being that low before... but maybe I'm just getting senile. Could the gauge be bad or just wrong?

thanks
dan

 

[tcartwri]

Not familiar with that engine, but low pressure can be caused by an oil filter bypass hanging open.

 

[Cpjlube]

I think that had the z134 engine. Specs I see say no lower than 15psi and 20 to 30 psi at 2200 rpm. Sounds like you are on the low side.
The relief valves can get sticky. You might try bleeding the oil pressure line near the gauge to make sure you don't have air in the line.
I would exhaust all options before a tear down.
I would change the oil and filter and run the tractor for 1/2 hour or so. If the oil pressure holds steady at around 20psi I might just put off tearing it down. It's at the low spec but not below acceptable. If after running a while, the oil pressure drops, then pull the pan and check relief valve and check clearance on main and rod bearings. If bearings are within specs I would replace oil pump and valve. Usually relief is on the pump anyway.

 

[buickanddeere]

What weight of oil? How many hours since rebuild ? Straight weight oils hold pressure better than multi weight . It's summer, 50wt will be fine .

 

[KennyG]

Good suggestions above. If it holds steady pressure at idle, but doesn't rise much when the engine speed increases, bypass valve is likely cause. However, it's nothing to panic about. As long as you keep a steady 20psi or so, nothing will get damaged.

 

[pmsmechanic]

In school we were taught that 10 lbs of pressure/1000 rpm is adequate. I don't know what rpm your tractor has at full throttle but you should be close. If your concerned you can just run a slightly thicker oil. Ie 10w30 or a 15w-40 instead of 5w-30. Or as has been suggested use a straight grade oil.

I've used diesel oils in gas engines for many years already. If you use a 15w-40 diesel oil in a pumping unit (used for irrigation) instead of a straight 30 oil the 15w-40 oil runs 10F cooler. To me that is a indicator of less friction.

Before you get too worried I would check the gauge. Just because it's new doesn't mean it's accurate.

 

[Danbo56]

Wow... thanks for all the great advice! I inherited the tractor with 2200hrs on it. I don't know much about it's history prior to the 2nd owner who got it with ~1500 hrs on it around 1990. It runs great. I just did a bunch of superficial freshening ( oils, fluids, tune up, carb rebuild, wiring harness, fresh paint, etc....) Before I spent $$ we did compression test, oil analysis and a good look. I didn't wanna throw money into a pit.... So, now I'm committed and I'd hate to blow it up.
I think I will start with the one new thing in the oil pressure equation... How do you check for air in the oil pressure line?

 

[pmsmechanic]

How do you check for air in the oil pressure line?

Actually if there is air in the oil pressure line the only thing it will do is cause the gauge to indicate pressure slower. The air in the line to the pressure gauge is the same pressure as the oil in the line. If you are concerned about it just take the line off at the gauge and crank the tractor over till oil comes out of the line and then reattach it.

 

[Jerry/MT]

What is the normal operating oil pressure for a Mf50 with a continental gas engine?
I put new gauges in... including the oil pressure gauge but now I'm noticing that the oil pressure never exceeds 20 . I don't remember it being that low before... but maybe I'm just getting senile. Could the gauge be bad or just wrong?

thanks
dan

The usual causes for low oil pressure are worn bearings, worn oil pump, or a stuck open pressure relief valve. The Z series Continentals call for nominal oil pressure to be 25-30 psi with minimum pressure of >15 psi at 400 rpm idle with a warmed up engine.
I'd check for a stuck pressure relief valve first. You'll have to pull the pan for that.

pmsmechanic is correct; air in the oil pressure line will not affect the oil pressure gauge reading

 

[Danbo56]

Ok... This will be a learning experience.
I ordered a new gauge on the odd chance that the current one is wrong. What the hey...it was $22.
I'm going to assume that the pressure relief valve is stuck open. So, I have to pull the oil pan. I've never worked on a tractor, I'm not a mechanic and I did not sleep at the Holiday Inn Express last night. You see where this is going...
1. Does the pan just unbolt and slide off like a car?
2. How do I know the relief valve is stuck open?
3. I'm looking at the shop manual, if it is stuck open how do you fix it?