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Tractor Talk Discussion Forum

Oil pressure question re:JD 850 w/Yanmar engine

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DAN9-Midwest

06-10-2007 19:21:22




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I bought an 850 JD recently and after I work it hard the oil light flickers at lower idle. It's a late 1980's 3 cylinder Yanmar engine and has 1200 hours. What should I start looking for or can someone point me in a direction? I do not have much money invested it I so figured I could maybe drop off at dealer and have them diagnose? I like the tractor and would like to keep it.




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37 chief

06-11-2007 16:33:26




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 Re: Oil pressure question re:JD 850 w/Yanmar engin in reply to DAN9-Midwest, 06-10-2007 19:21:22  
Your manual should say what the oil pressure should be at a certin RPM. I have a JD 5020 with the correct oil presssure at operating RPM. but drops way down at idle to almost nothing. I like to see good oil pressure, but sometimes you need to take the good with the bad. Like someome else mentioned use 40 wt. diesel oil. Stan



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Mike M

06-11-2007 05:08:29




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 Re: Oil pressure question re:JD 850 w/Yanmar engin in reply to DAN9-Midwest, 06-10-2007 19:21:22  
I am pretty sure those Yanmars have adjustable oil pressure too ,so you may be able to turn it up some.

I agree with the others,put in NEW oil and filter and hook up a real gauge to it to be sure where it's at.



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DAN9-Midwest

06-11-2007 03:28:54




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 Re: Oil pressure question re:JD 850 w/Yanmar engin in reply to DAN9-Midwest, 06-10-2007 19:21:22  
Thank you all. I had changed the oil and filter with typical 15W40 diesel oil. Maybe Rotella. No water in oil but I will hook a gauge to it. Thanks again, very helpful.



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Davis In SC

06-10-2007 20:32:25




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 Re: Oil pressure question re:JD 850 w/Yanmar engin in reply to DAN9-Midwest, 06-10-2007 19:21:22  
Is there any sign of water in the oil ? Some Deeres of that vintage were prone to getting coolant in the oil via a bad sleeve O-ring. The coolant in the oil dissolves the bearings, causing low oil pressure.



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Bob

06-10-2007 19:51:50




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 Re: Oil pressure question re:JD 850 w/Yanmar engin in reply to DAN9-Midwest, 06-10-2007 19:21:22  
Change the oil and filter. Note if the oil seems to have been diluted with diesel fuel. (From a fuel system problem.) Temporarily connect up a mechanical gauge, and see how much oil pressure you REALLY have.

Those are a GOOD engine, and, unless it's had an unusual problem, or been seriously abused, I'd suspect a bad oil pressuure sender WAY before a serious engine problem.

If you are LUCKY, it will turn out to just be a bad oil pressure sender... DEERE part # M810001, @ under $13.00. I ASSUME they fail from time to time, as the local dealer stocks them.

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delta bob

06-10-2007 19:35:10




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 Re: Oil pressure question re:JD 850 w/Yanmar engin in reply to DAN9-Midwest, 06-10-2007 19:21:22  
Change the oil and filter, be sure to use diesel oil, 40wt oil will increase the pressure a little. You may want to change the oil pressure sending unit.



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omahagreg

06-10-2007 19:25:27




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 Re: Oil pressure question re:JD 850 w/Yanmar engin in reply to DAN9-Midwest, 06-10-2007 19:21:22  
Has the oil been changed recently? If not sure, or definitely no, I would change the oil and filter first, before asking for any more diagnostics. Greg



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mark

06-10-2007 21:05:51




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 Re: Oil pressure question re:JD 850 w/Yanmar engin in reply to omahagreg, 06-10-2007 19:25:27  
Two years ago, I sold my JD 1050 after 20+ years of faithful service....yet it only had 1500 hours on it! I mowed the grass and plowed the garden with it. I started having the same trouble you are. I had babied that little tractor from day one, always kept in the barn, changed oil twice a year and it never did a hard days work while I owned it. I suspicioned the oil pump....no way the mains could be bad! I ordered one and went to the service dept. and asked for a copy of their repair manual pages. The mechnic asked me why I thought it was the pump? I explained myself and he said....."well, if it were me, I'd take that pump back to parts and get my money back. Your pressure is held on the mains in that engine (some engines the pressure is measured on the cam bearings) and that is where your problem is." So, I get a spec sheet and go home..without the new pump. I tap a gage in at the pump and at cold start up, it held 60 psi. But as it warmed, it began to fall. The idiot light comes on at 25 I think...and mine held 23 pounds....and the light was flickering. I believe it was supposed to hold 40 at idle and warm. Anyway..... the gage told the story. The mains had wear. Why at 1500 hours? I cannot say. So, I sold it, told the guy why and he is still running it and happy as a lark. Just set the throttle higher and the light goes out as pressure builds. No, it won't heal itself and will only get worse. But, in the 1950's, Chevy trucks idled at about 6 pounds pressure and I guess that was enough. If i wasn't in too deep on that 850, I'd just keep running it...fast enough to keep the light off and forget it. When you go buy parts and overhaul it, you'll spend big bucks. I was told there is very little meat in a Yanmar crank to regrind if it's scored or out of round. They priced me a new crank at $750.

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