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?

 

[Jerry/MT]

Frst of all you are dealing with late1940's early 1950's technology in an MF50 engine. It's not the Space Shuttle or the F-22! So don't let that scare you.

You don't know the relief valve is stuck open. It could be a worn oil pump or worn bearings. In my opinion, however, the easiest thing to do is to check the relief valve. First spend the bucks to buy a factory manual for your tractor. At $100/shop hour, the book will pay for itself with the first repair you use it for. It will explain how the systems wok and if the repair job is too much for you to do, you can figure it out from the manual before you start something you can't finish.
I have no direct knowledge of the MF 50 but I am familiar with the Z series Continental engines that power them. They have a relief valve built into the oil pump and it has a relief valve that you can access once you remove the oil pan. Since I'm not familiar with the MF50, I can't say how easy the oil pan is to remove but it can't be that difficult. You drain it, remove the bolts, and remove it. The oil pump (a simple gear pump) is driven by the timing gears, The relief valve spring is held in place by cotter pin through the discharge passage. On top of that spring sits a small piston that fits the passage. You remove that cotter pin and the spring and piston should slide out. If the piston is stuck, you'll need to work around it with a small wire to free it and then get as much of the crud out as you can. The spring usually has a certain free length and some times the spring gets damaged. You can buy a new one and it should be cheap. When you clean the passage out you merely put the piston in, then the spring and then the cotter pin. While you have the pan off, you can buy some Plasti-Gauge and check the clearance on the main bearings. Compare them with the nominal clearance. If the clearances are above the allowables, you've found your problem. Now you have a decision to make. Replace the mains. If the mains are good, then replace the pan, fill with oil and see if the pressure is near normal. If it is, you've fixed the problem and you'll know the mains are good. If you still have low oil pressure, a pump replacement is in order.

 

[Danbo56]

Thanks for the advice and vote of confidence.
I changed the filter and bumped the oil to a higher viscosity. No change in pressure. I'm still reading ~15psi at 500rpm and 18psi at anything faster than ~1000rpm. I will try a new gauge. If that doesn't solve it, off comes the pan.

 

[Danbo56]

ok... I put a new gauge on. At ~800rpm I have 15psi anything above 1200rpm produces ~18psi. At 2000 rpm still 18psi.
I'll pull the oil pan and look at valve. What am I looking for? Should I replace the spring?

thanks !

 

[Bladehauler]

I believe that continental has only a bypass filter , so the screen on the pump is the main filter. if the tractor runs fine and pulls loads without complaining, I would drop the pan and install a new pump and run it !

 

[Danbo56]

I see the oils pump repair kits run ~$80 on Steiner. But Walts tractors has a replacement pump for $57 . Is it easier better to replace the pump? Interesting... the rebuild kit is more than a new pump?

 

[Jerry/MT]

ok... I put a new gauge on. At ~800rpm I have 15psi anything above 1200rpm produces ~18psi. At 2000 rpm still 18psi.
I'll pull the oil pan and look at valve. What am I looking for? Should I replace the spring?

thanks !

I would remove the spring and the piston and try to clean the passage so that the piston moves freely. Check the spring length against the spec. If it's good than re-install it. If not, replace it. I believe tou can also put washers under the spring to increase the spring force and hence the relief pressure. Check the manual before you pull the pan.

 

[Danbo56]

Update.
Since I was getting ~18psi at 1800 rpm I was going to hold off doing anything for now. BUT.... I started the tractor on Sunday to mow a pasture and I had only 10 psi at 1800rpm, less at an idle. I drove it over to the house thinking that's a better place to take it apart. The engine sounds fine no abnormal noises.
Time to drop the pan and see...

 

[WilliamTO-35]

I just bought a new set of gauges that fit my TO-35 . Every gauge was way off in calibration. The oil pressure gauge read 15 pounds low , as compared to four American made high quality gauges I use for calibrations, using air pressure. I had to uncrimp the gauges around the perimeter, remove the mechanisms, and recalibrate every gauge ! These three gauges were all from different sources, although two of them were made in India.
The third one was made in China. Even General Motors is now using some replacement gauges made in India ! Junk, all of them.

 

[Danbo56]

Yeah.... I'm not impressed with the Indian made stuff. I'd gladly pay more for US or EU made parts

 

[Danbo56]

Coodos to Jerry/MT....
I took it to a friend who heavy equipment engine mechanic. It was the pressure relief valve just as described by several others. The spring was 3/8" short and the valve was stuck. He rebuilt the pump. Checked the bearings... all good. So... now I have 35 psi at 2000rpm. :thumbsup: