MF 35 - Oil Pressure Problem

Kentucky Bob · Mar 23, 2009

Well Guys,
This past weekend, it was dry enough for me to try out my "new" 35 and bush hog. Here"s what happens.
When I first start it, the oil pressure goes up to about 80. After it warms up enough to start working the tractor, it drops down to about 40. Then, when I get into the bush hoging, it goes to between 20 and 30. According to the book, that"s about right.
Then, shortly after that, it drops down to about 6 or 7! And even without the book, I know that ain"t good.
Questions;
1. Could it possibly be the oil pressure gauge? I read that I can get a external gauge and tap into the line that goes to the oil pressure gauge, and get a reading. Is that even worth trying? I would love for that to be the problem, but I"m guessing it isn"t.
2. Oil pump?
3. Main Bearing?
Any ideas as to what to check first, or what your best guess is would be appreciated.

Thanks.

Gerald S. Eggart · Mar 23, 2009

My experiance..... limited to my MF203 (Perkins Diesel) is that it will end up being the bearings. Some other things I"d check.

With the engine running, remove Oil dipstick..... does oil bubble out the hole? If yes, you probably need rings to. Next, after your hour or 2 of brush hoggin.... assuming you started with fresh oil.... was it black? Could be another sign of blowby.

Good news is that after you spend $$$ on a rebuild..... The thing will run for as long as you own it!

Hope this helps!

Looking for MF tractor manuals.... try www.freetractormanuals.net

-Gerry

maxwell99 · Mar 23, 2009

try another oil pressure gauge first, should run about 25-30 psi.

might try: change the oil, warm engine so most of the old oil runs out. Install shell rotella 15-40 and 1 qt of lucas oil stablizer.

be sure the oil filter spring and washer are in the oil filter canister.

use a top quality filter, either an AC/Ferg or wix/NAPA gold.

worth a try before you start tearing it down.

Tony in Mass. · Mar 23, 2009

Yeah, before you tear things appart, I had -still have, an Ac that had no oil pressure when I bought it. It has a lot of small diameter outside oil lines. I took them off, ramrodded with mig wire and blew them out- inside and outside lines and channels- with a needle attachment, nice high and steady pressure since. Fergies don't have much for outside lines, but see what you can do with this too. 50 years of crap in there?

Jerry/MT · Mar 23, 2009

Since you are reading various oil pressures on your gauge, I don't believe the gauge is the problem. Your problem appears to me to have several possible causes.

You could have a stuck open relief valve, a worn oil pump, or worn bearings or all of the above.

When you start up the oil is cold and the oil viscosity is high so you get a high reading. As your oil temperature increases, the oil vicosity decreases and the oil pressure decreases. Finally when you are at a stabilized operating temperature you oil viscosity is at a minimum and your oil pressure is low. Does the oil pressure change between idle and operating rpm?

I would check the oil pressure relief valve first. Make sure that it operates freely and is clean and not crudded up. A good shop manual will tell you what the relief spring "free" (uncompressed)length should be. Then put it back together and test it. If you oil pressure is ok, your done. If it's not, go on to the oil pump.

To check the oil pump you'll need a shop manual with the specs in it. You can generally measure some clearances and then compare them to allowable clearances. If you can't find any specs you can decide to replace the pump or just go on to check the mains.

Finally, you can plastigage the mains and see if they are within spec. If you have to redo the mains then replace the pump at the same time. That's just good practice.

That's what I would do if this was my tractor. I have a TO-30 with about 500 hrs on a reanufactured engine and it's spec is pressire >15 psi at hot idle. My machine runs 27 psi at all rpms from idle to max, hot or cold, in all ambient temperatures with 10W40 oil. My relief valve controls that and that's why I know it's working.

Pacer204 · Oct 23, 2014

(quoted from post at 04:31:59 03/24/09) Since you are reading various oil pressures on your gauge, I don't believe the gauge is the problem. Your problem appears to me to have several possible causes.

You could have a stuck open relief valve, a worn oil pump, or worn bearings or all of the above.

When you start up the oil is cold and the oil viscosity is high so you get a high reading. As your oil temperature increases, the oil vicosity decreases and the oil pressure decreases. Finally when you are at a stabilized operating temperature you oil viscosity is at a minimum and your oil pressure is low. Does the oil pressure change between idle and operating rpm?

I would check the oil pressure relief valve first. Make sure that it operates freely and is clean and not crudded up. A good shop manual will tell you what the relief spring "free" (uncompressed)length should be. Then put it back together and test it. If you oil pressure is ok, your done. If it's not, go on to the oil pump.

To check the oil pump you'll need a shop manual with the specs in it. You can generally measure some clearances and then compare them to allowable clearances. If you can't find any specs you can decide to replace the pump or just go on to check the mains.

Finally, you can plastigage the mains and see if they are within spec. If you have to redo the mains then replace the pump at the same time. That's just good practice.

That's what I would do if this was my tractor. I have a TO-30 with about 500 hrs on a reanufactured engine and it's spec is pressire >15 psi at hot idle. My machine runs 27 psi at all rpms from idle to max, hot or cold, in all ambient temperatures with 10W40 oil. My relief valve controls that and that's why I know it's working.

I have a similar problem with a MF35X. Can the pressure relief valve be serviced without removing the sump?

Thanks

ptfarmer · Oct 23, 2014

(quoted from post at 09:41:47 10/23/14)
I have a similar problem with a MF35X. Can the pressure relief valve be serviced without removing the sump?
Thanks

You have to remove the sump to get at pressure relief valve. You don't have to split the tractor at the engine/transmission, but it does help to support the tractor at the clutch housing, and loosen the bolts on the front support some so you can move it forward just a little bit (about 1/8 of an inch is enough, 3mm for the metric guys). The little extra clearance at the front makes pulling/installing the sump easier.

MF 35 - Oil Pressure Problem

Kentucky Bob

New User

Gerald S. Eggart

New User

maxwell99

Well-known Member

Tony in Mass.

Well-known Member

Jerry/MT

Well-known Member

Pacer204

Member

ptfarmer

Well-known Member

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