1974 MF 135 Diesel Losing oil pressure

[TTownvet]

Thank you for accepting my application. I bought a 1974 MF135 perkins diesel a few months ago. Tractor starts on 2nd or third rev every time, runs up smooth and sounds great. Paint was gone, gauges were all frozen or broken (except tach which was new showing 33 hrs). Seller suggested previous owner indicated the engine had been overhauled a few years earlier and few hours had been put on it since. I know, I know but I only paid around $2700.00 for it so I went in with my eyes open. She sounded sooo good also. Sheet metal was solid with surface rust and mechanically the the tractor was solid so I invested some time and finished and repainted the tractor. Also replaced the gauges. I went to put it to work on the hunting club and this is where I need some help from any MF 135 experts out there, When first started the oil pressure reads in the upper 2/3 of green (no numbers on gauge). Over 20-25 min of working at 1900-2000 rpm (bush-hogging) the oil pressure slowly drops all the way down into the red (near zero). During this time the tractor sounds fine (no change in sound) ,never loses any power and continues to run cool. In fact it never really even gets up into the green on the gauge. I checked the gauge in boiling water before installing it and it worked fine. Thinking maybe my gauge was faulty I crossed my fingers and continued to work for about 6 hrs listening carefully and watching the temp which never changed. Never smoked or lost power or sounded funny. I had changed all fluids and oil filter and was running 10w40 deisil oil. I got home and deciced to change to straight 30w oil but with the same result except the oil pressure maybe was slightly higher but not much. I want to blame the gauge but it reads fine when first cranked. Also allowing the tractor to sit for as little as 5 min will cause the gauge to come up significantly when restarted (although it somewhat quickly begins to drop again). So I don't know if: 1) Faulty gauge 2) Worn oil pump (but pressure is high at first?) 3) Sticky relief valve 4) Excessive rod and main bearing wear. Any ideas.... I'm reasonably mechanical but not a lot of experience on tractors. Thank you so much for any help!

 

[m16ty]

It could be any of the things you mentioned above. What's happening is the oil is getting warm and can make it harder to pump, easier to flow past worn bearings, or seep past your relief valve, any of which can cause low oil pressure.

First thing I'd do is check the gauge, it's normal for even a new engine to have a oil pressure drop once it warms up, but it shouldn't drop that much. Almost all of these reproduction gauges come from China now, and they are notorious for reading wrong.

Other than that, you're going to have to check what's going on inside the engine. I have a tractor with the same engine (MF40 industrial) but it's been so long since I've been into the engine I don't recall much about the oil flow. I do know it's quite a job to drop the oil pan, which also doubles as the tractor frame.

 

[TTownvet]

Thanks M, yep I think ill get a test gauge and plug it into the oil galley where my gauge line comes out and run the tractor for 20 or so min and see what happens. Thatll take the oil line out of the equation as well. Ive heard of people adding a quart of atf to the crankcase and running it to flush the system? Ive never tried that. And youre right it looks like a royal pain to drop that pan. Esp since right now I dont have a shop so Id be working on it in my carport.

 

[[email protected]]

I would also be curious to what weight oil you have in the engine. Most of these were a straight weight of SAE30. If you're running a 10w30 or the like, you will have thinner oil when the engine temps rise. If your guage pressure is valid, I would focus on the bottom end of the engine. Main bearings tend to either hold or lose pressure when it comes to oil. Worn or out of spec mains, pressure drops. Not saying that is your particular problem, just my experience.

 

[m16ty]

If it was in fact rebuilt properly like the previous owner said, it could be the oil pump, thinking maybe they didn’t replace the pump at rebuild.
To drop the pan you have to pull everything off ahead of the engine, radiator and front bolster.

 

[John Deere D]

Thank you for accepting my application. I bought a 1974 MF135 perkins diesel a few months ago. Tractor starts on 2nd or third rev every time, runs up smooth and sounds great. Paint was gone, gauges were all frozen or broken (except tach which was new showing 33 hrs). Seller suggested previous owner indicated the engine had been overhauled a few years earlier and few hours had been put on it since. I know, I know but I only paid around $2700.00 for it so I went in with my eyes open. She sounded sooo good also. Sheet metal was solid with surface rust and mechanically the the tractor was solid so I invested some time and finished and repainted the tractor. Also replaced the gauges. I went to put it to work on the hunting club and this is where I need some help from any MF 135 experts out there, When first started the oil pressure reads in the upper 2/3 of green (no numbers on gauge). Over 20-25 min of working at 1900-2000 rpm (bush-hogging) the oil pressure slowly drops all the way down into the red (near zero). During this time the tractor sounds fine (no change in sound) ,never loses any power and continues to run cool. In fact it never really even gets up into the green on the gauge. I checked the gauge in boiling water before installing it and it worked fine. Thinking maybe my gauge was faulty I crossed my fingers and continued to work for about 6 hrs listening carefully and watching the temp which never changed. Never smoked or lost power or sounded funny. I had changed all fluids and oil filter and was running 10w40 deisil oil. I got home and deciced to change to straight 30w oil but with the same result except the oil pressure maybe was slightly higher but not much. I want to blame the gauge but it reads fine when first cranked. Also allowing the tractor to sit for as little as 5 min will cause the gauge to come up significantly when restarted (although it somewhat quickly begins to drop again). So I don't know if: 1) Faulty gauge 2) Worn oil pump (but pressure is high at first?) 3) Sticky relief valve 4) Excessive rod and main bearing wear. Any ideas.... I'm reasonably mechanical but not a lot of experience on tractors. Thank you so much for any help!

A neighbor of mine owns a MF 135,3 cylinder diesel Perkins. He asked for my thoughts on why the engine was indicating low oil pressure after an engine overhaul ,(gauge needle left of center )with engine coolant up to 180F, with 15-40 oil and two hours running time.
When I asked, "what did a micrometer tell you when you checked the crank journals"? He never checked the Journals! Did you install a new oil pump from either Perkins,or Massey Ferguson?
A FRIEND of his said "do not waste your $$$'s"!
I suggested he talk to a Certified Tradesman,not a self taught shade Tree practitioner.
He had all the journals ground under size,and a new engine oil pump.
Now Engine oil pressure is like my MF 35 X 3 cylinder Perkins Diesel,. With the PTO at 540 RPM,engine around 1500 >1700 RPM,engine oil pressure is full scale to the right in the gauge.

 

[TTownvet]

I would also be curious to what weight oil you have in the engine. Most of these were a straight weight of SAE30. If you're running a 10w30 or the like, you will have thinner oil when the engine temps rise. If your guage pressure is valid, I would focus on the bottom end of the engine. Main bearings tend to either hold or lose pressure when it comes to oil. Worn or out of spec mains, pressure drops. Not saying that is your particular problem, just my experience.

Dave, at first I had 10w40 in it but then thought like you and changed to straight 30w however the prob persisted.

 

[TTownvet]

A neighbor of mine owns a MF 135,3 cylinder diesel Perkins. He asked for my thoughts on why the engine was indicating low oil pressure after an engine overhaul ,(gauge needle left of center )with engine coolant up to 180F, with 15-40 oil and two hours running time.
When I asked, "what did a micrometer tell you when you checked the crank journals"? He never checked the Journals! Did you install a new oil pump from either Perkins,or Massey Ferguson?
A FRIEND of his said "do not waste your $$$'s"!
I suggested he talk to a Certified Tradesman,not a self taught shade Tree practitioner.
He had all the journals ground under size,and a new engine oil pump.
Now Engine oil pressure is like my MF 35 X 3 cylinder Perkins Diesel,. With the PTO at 540 RPM,engine around 1500 >1700 RPM,engine oil pressure is full scale to the right in the gauge.

JD I have not torn into the engine yet, May well have to happen but that would be a Big job considering the facilities I have at my disposal.If I cannot resove the issue I may hve to do whatever it takes to drop the pan and get the old Plastigauge out.

 

[m16ty]

JD I have not torn into the engine yet, May well have to happen but that would be a Big job considering the facilities I have at my disposal.If I cannot resove the issue I may hve to do whatever it takes to drop the pan and get the old Plastigauge out.

Getting the pan off is actually the hardest part, after you do that everything is right there to check and replace if needed. No need to take the engine completely out of the tractor or remove the head for just a oiling problem.

Something else that just crossed my mind is cam bearings. Often a tractor will just get a "in-frame" rebuild where the piston, sleeves, rod bearings, and main bearings replaced, but they don't pull the cam to replace the cam bearings. If you can't find any problems that would cause low pressure from the bottom, you may have to pull the front cover and the cam, which isn't that big of deal at that point since you already have the front of the tractor removed.