what is normal oil pressure ?

[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: