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TheFastMan
Frequent Contributor

John Deere oil pressure problems

Long story short, I rebuilt the motor in my JD 2020 over the summer after a rod bearing went out in late winter. We got the motor back in on Monday and fired it up on Wednesday/Thursday. It seems to run fine, but we have low oil pressure. I think it's at about 15psi at wide open. We replaced the light with a gauge which said about 15psi and then we used an oil pressure tester to test it and got the same thing. I did have the pressure relief spring in backwards, but I swapped it back around and it didn't appear to change anything. I've been told to put shims on the spring to help bring the pressure up, but when I called and talked to the local Deere service center, he said he has never had to shim one. It doesn't seem to be leaking oil anywhere, but I will do a thorough search tomorrow if I have the time. The Deere dealer also told me it could be the wrong bearings on the crank, but I am 99.9% sure that I got the correct ones (10 over for rods and mains). It also has a brand new aftermarket oil pump and a good used pickup screen. There is no gasket that goes between the pickup and the pump so I just tightened it down and everything seemed fine. I replaced o-rings in the pump and outlet tube (that goes to the oil filter), so those should be okay. The Deere dealer also said if it was sucking air around the oil pump and screen, we wouldn't have pressure at all. Also, when you take the fitting out of the block where the pressure gauge screws in, oil will shoot out about 6 or 8 feet (1/8in NPT hole). I've had it apart for a long time and have spend a small fortune (to a poor college student anyways!) on rebuilding it right and now it's kind of frustrating to be so close to being done and having a big problem like this pop up. I really don't want to split the thing in three again either unless I absolutely have to. Any help, direction or advice is greatly appreciated. Thanks!

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12 Replies
onebigbyrd
Veteran Contributor

Re: John Deere oil pressure problems

i would think  even if you had the wrong bearings you could change them without a disasembly. take the pump off and put the pick up in some oil, then turn the gear and see how much resistance you have

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Pat in CMO
Senior Contributor

Re: John Deere oil pressure problems

 I have never seen an oil pump pickup that bolted on and didn't use a gasket or something to seal it up. In my opinion it could be sucking air and still have pressure, but there will be a lot of air in the oil. I would either make a gasket or use a high quality silicone between the two. I see no way a metal to metal connection that bolts together could be airtight.  Patrick

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nwobcw
Advisor

Re: John Deere oil pressure problems

  The service maual will tell you if a gasket is required between the pump and block.  Pull a rod cap off and mic it to be sure the right bearings are in it.

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nwobcw
Advisor

Re: John Deere oil pressure problems

  I meant mic the bearing insert.

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TheFastMan
Frequent Contributor

Re: John Deere oil pressure problems

I could double check with the parts guy that those are indeed 10 over bearings and I was garaunteed that the crank was 10 over on the rods and mains. Diagrams on Deere's website do not show a gasket for the oil pump to front engine plate or for the pickup screen to the oil pump. It thought it was kind of weird also. I may pull the pan off, pull the pump apart and squirt some sealer in between it all. Also, we may have about 10min total of run time on the thing. Would that be enought time for all the assembly lube to burn off? Would letting it warm up to temperature make any changes? I think I will get a new pressure relief spring and valve. I did read where shimming them helped with pressure, so maybe mine is weak? Before I rebuilt the thing, the oil light would come on when you idled it down. It would start flashing when you got the lever about 2/3 of the way down. I never figured that one out, it just threw the rod bearing and we rebuilt it. The old oil pump, however, was quite worn and well past it's service life. Maybe I should buy a brand new pick up screen and quite screwing around with used parts also.

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TheFastMan
Frequent Contributor

Re: John Deere oil pressure problems

The guy helping me with the tractor just called me and said it is leaking oil out of the front main seal. They are brand new seals. He says he is going to try some a seal conditioner additve to see if that helps. Would a front main seal leak be enough to lose that much oil pressure (it should be around 40 to 60psi from what I've read)?

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siloguy
Frequent Contributor

Re: John Deere oil pressure problems

The front seal leak, while annoying, should make no difference on oil pressure. I am guessing if it is new, the conditioner won't help. If it is one of them annoying rope seals, you have my sympathy! You may be onto something about the pressure relief spring being weak. Even 15 psi will throw oil a long way so I think your new gauge is right. Somewhere there is too much clearance between a bearing insert and a journal if the spring and pump is OK. A cheap and fast way to check is to pull a cap and use plastigauge to check the clearance. Your crank is more likely to be 10 under instead of 10 over, as grinding a crank tends to make them a bit smaller. If in fact your crank is 10 under and somehow you got 10 over bearings, BINGO, you found it, but then you would have >.020 plus clearance which would be terribly loose! Other places that a worn engine can lose oil pressure are the cam bearings and the rocker assembly, but the crank is the main culprit. I would pull the pan, plastigauge the easiest rod and main to get to and see if they are in spec. If they are, change the spring. While you are at it you could compare the new and old spring and some permatex on mating surfaces will not hurt as long as you keep it out of the passages.

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TheFastMan
Frequent Contributor

Re: John Deere oil pressure problems

Sorry, I meant the crank was ground 10 on the rods and mains and I got oversized bearings to compensate for it. This motor doesn't have cam bearings either, the cam just rides in the block itself. We did get some paint on the front engine pulley (the one that fits on the crank and seals on the front main) before it was all the way in. Could that be causing the front main leak? I think I'll just buy a new spring and valve and see if that's the culprit. It's really the easiest to get to. I think I'll pull the pan also and take a look around.

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siloguy
Frequent Contributor

Re: John Deere oil pressure problems

Yeah, paint on the sealing surface could do it. It should be polished pretty smooth with no deep grooves in it.

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