low oil pressure after overhaul

1badMF · Mar 16, 2019

I picked up my tractor today after the motor overhauled. The tractor is a 1961 MF 35 with the perkins diesel. The motor was pulled and completely rebuilt with all new bearings, pistons, ect. The tractor idled for about 15 minutes then I hooked up a bush hog and began to do some mowing. After 30 min or so I noticed the oil pressure gauge was reading right on the red and green line on the low end of the gauge. I stopped working and headed back to the barn and shut it down. I talked to the mechanic and he said the gauge could be back or it could be because of the break in oil. He told me he hooked a digital gauge up to it when he was running it and the oil pressure was good. Any ideas what could be causing this? Thanks!

tlock0331 · Mar 16, 2019

cam bearings maybe? i think he is right, hook up a known good gauge and see what it says....

tomstractorsandtoys · Mar 16, 2019

Put a guage with numbers on it untill it is broke in. I also agree that you will have lower oil pressure with break in oil. Tom

1badMF · Mar 16, 2019

Thanks for the quick replies. Would it be safe to operate with the gauge reading like it is with the needle being on the low/good line? Also the gauge was about 12 o'clock while it was idling and I first started working. Then dropped after a half hour or so. It was doing this same thing prior to being rebuilt also.

FBH44 · Mar 16, 2019

Admiral Rickover always said; "Always believe your instrumentation!"

Steve@Advance · Mar 16, 2019

You definitely want to keep the mechanic who did the work in the loop on this. Don't do anything without him knowing and approving it first.

Did you notice what the pressure did when it was at idle and up to temperature?

If the pressure drops dramatically at warm idle, something is wrong.

That information, along with readings from a known good gauge will tell if it is in tolerance. The acceptable oil pressures are in the service manual, something you need to find out beforehand. Someone on here will probably be able to find that for you.

Again, I would ask the mechanic, let him run the tests, and be sure the test is done when thoroughly warmed up.

37chief · Mar 16, 2019

What does the mechanic mean by good? What you are seeing on your gauge isn't good, to be sure of a good gauge. would hook up another gauge, then go back to the mechanic. Stan

MSM · Mar 16, 2019

Put a good known accurate gauge in it,and only run it enough to get your pressure readings. Don't try and use it until you know the oil pressure is good

rustred · Mar 16, 2019

you need to use a master guage to check OIL PRESSURE in PSI. this good and bad is useless info. then post the readings in psi u have got. at idle and full throttle.

rustred · Mar 16, 2019

also it don't matter what oil u have in it, it will not drop from the the high side of the guage to the low side. depending on oil weight it might max out at a SLIGHTLY different position and move very little when hot. so if he is saying due to break in oil he is pulling wool. you have oil pump or brg. problems. did he replace camshaft brgs.??

fastfarmall · Mar 16, 2019

I agree with rustred, and chances are it's not a bad gauge, there the most foolproof thing on a equipment!

sotxbill · Mar 16, 2019

Is fuel getting into the crankcase and thinning the oil?

what kind of break in oil did he use?

1badMF · Mar 16, 2019

15-40

1badMF · Mar 16, 2019

I don't think the kit came with cam shaft bearings. I know he replaced the main bearings for sure

fastfarmall · Mar 16, 2019

What happened to me once, the parts guy give the mechanic the wrong bearings,the crank was cut 10 thousand's and the parts guy grabbed standard bearings,give it to him, and the mechanic never looked at the box, put them in, and i would lose oil pressure to when the oil got warm. I had too shut it off walk away, restart it, mow some more, till i lost oil pressure again !!

fixerupper · Mar 16, 2019

I have a gut feeling the wrong bearings were put in. The oil would have to be as thin as kerosene to make a pressure drop like that in a healthy new engine with the proper tight tolerances. It’s not the gauge but you could check it with another gauge just for the fun of it.

gbs · Mar 16, 2019

as others said try another gauge to start with,if that confirms low pressure it could be anyone of the conditions mentioned, but what sounds odd is the length of time it ran before the pressure dropped i had a mf 230 less than 2 years old all of a sudden it started losing pressure when i dropped the pan and started hunting the problem i found the oil pump relief spring had broken was the problem

WGM · Mar 16, 2019

I?d have your ?mechanic? pickup the tractor with instructions to the mechanic let you know when the oil pressure issue is verifiably repaired. If you need a tractor in the meantime your mechanic should provide you with one. If he doesn?t own one for you to use he can rent one. Hope you haven?t paid him yet.

rustred · Mar 16, 2019

well there you go!!! camshaft brgs is your problem. why u say replaced all brgs.??? we never get complete info here.

SVcummins · Mar 16, 2019

Check it with another gauge and see what it reads . If it was doing it before and it?s still doing it did the mechanic rebuild or replace the oil pump ? I rebuilt a 4020 diesel one time that did the exact same thing you described I replaced the oil pump and problem solved

1badMF · Mar 16, 2019

I talked to the mechanic and I think we're going to replace the oil pump. He is telling me that particular motor doesn't have cam bearing and the cam was checked by the machine shop.

kencombs · Mar 17, 2019

(quoted from post at 23:03:18 03/16/19) I talked to the mechanic and I think we're going to replace the oil pump. He is telling me that particular motor doesn't have cam bearing and the cam was checked by the machine shop.

I know very little about that particular Perkins, but less than 30 seconds on Google found the part number for the cam bearing set.

Something's fishy with the mechanics story or knowledge.

Oliver 500 Wa · Mar 17, 2019

A "mechanic" without the tools and knowledge to measure all the clearances in the engine when assembling it is no mechanic IMHO. Relying on numbers marked on parts boxes or the claims of the machine shop is not doing the job properly.

SVcummins · Mar 18, 2019

1badmf Let us know how it goes will you ? My bet is it?s a bad oil pump

buickanddeere · Mar 18, 2019

Was the crank ground , new sleeves/pistons/rings, new injectors , new valves , reground cam, resurfaced lifers , new oil pump, new seats, test the valve springs and new cam bearings rebuild ?
Or was this a set of rings, a set of lower end bearings and grind the valves/seats ?

SVcummins · Mar 19, 2019

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low oil pressure after overhaul

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