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Discussion Starter #1
I've owned my 1995 JD 455 for about 3 years, and the oil pressure light came on yesterday for the first time. The light came on at low RPM idle, fading out at about 1/3 throttle. The light stayed off at higher RPM. I changed the oil a few weeks ago, and it only has about 1 hour on this oil change. I used Rotella 15W40 for diesel engines, same as before. I change the oil once per year (about 30-40 hours on each change). What should I check first?

Thanks,

Jon
 

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Kish JD 318/420/430
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Things to check:
Oil pickup might be covered with something.
Oil pan might have sludge build up enough not to allow oil to the pickup.
Check the oil pump pressure regulator/spring.

Is this a synthetic, regular or a blended oil. If a full synthetic you need to change the filter for one that is for a synthetic.
 

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The first thing I'd do is verify you have low oil pressure. You could simply have a failing oil pressure sensor. Get a low pressure gauge, 60 psi or less, remove oil sending unit and install gauge. If pressure is below (guessing here!) 5 psi at idle, you've probably got a problem...check/what as Russ suggested If 15 psi or so, probably a bad oil sender. Bob
 

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Kish JD 318/420/430
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I concur with Bob about testing with a pressure gauge, most senders/switches are made with plastic and other soft internals, life expectancy at most that I've had is 10 years. But you can tell easily due to the fact they are leaking oil sometimes a little sometimes a lot.
 

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Discussion Starter #5
Thanks for your suggestions. The oil I put in is a synthetic blend, because it was all the store had in a 15W40 that day. I had completely forgotten I did not use conventional this time around. I had to go back out to my garage to check. The oil filter is a Wix XP, which is rated for synthetic. I used this filter because my Hondas take the same filter as the Yanmar in the 455, and I have run synthetic in my cars for 10+ years. The synthetic blend oil seems thinner than the conventional of the same brand (Rotella) and weight. In addition, the temperature was in the 50s yesterday when the low oil pressure light came on, about 20 degrees warmer than any other time I've started it since I changed the oil. I am now wondering if this oil is too thin but the cold temperatures masked it before yesterday. I think I'm going to first change the oil back to a conventional oil and see if the light goes out. If it doesn't work, I'm only out 1/2 hour of my time and about $12.
 

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Kish JD 318/420/430
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Yes, I have to admit that synthetic seems to have flow characteristics different for the same viscosity (weight) in a conventional or blend oil and it puzzles me to no end. I think there has to be a better way or word to describe it. Then they say you need a filter that for synthetic (real expensive) versus the conventional from (cheap to expensive). If any one can clarify in simple English, it would help greatly. Maybe a video of full synth being pored right next to conventional and a blend.
 

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I've owned my 1995 JD 455 for about 3 years, and the oil pressure light came on yesterday for the first time. The light came on at low RPM idle, fading out at about 1/3 throttle. The light stayed off at higher RPM. I changed the oil a few weeks ago, and it only has about 1 hour on this oil change. I used Rotella 15W40 for diesel engines, same as before. I change the oil once per year (about 30-40 hours on each change). What should I check first?

Thanks,

Jon
Good Day Jon, I've run into this problem on 2 455's, and this may the solution to your problem. 1st check your pressure with a manual gauge. You should see 40 to 60 psi at speed. If the pressure is low, remove the oil pressure relief valve assembly, very easy. 3 bolts under the oil filter, remove the housing, you'll see the valve assembly. Look carefully at the valve and it's seat. I've found what looks like a small sliver of cast iron under the oil pressure regulator relief valve. Rotella 15/40 is super oil, and shouldn't cause this problem.
 

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Russ mentioned a special/certain filter when using synthetic oils. This is something that I've never heard of...so I Googled it!

Of the 5 or so articles I read, oil filters are not special for synthetic oil, they filter whatever oil goes through them. I did, however, find a comment about a "synthetic oil filter." This can be interpreted 2 ways: "synthetic oil" "filter" or "synthetic" "oil filter". The second interpretation is the correct one. These are oil filters made from synthetic materials.

This makes sense to me, but sometimes things that make sense to me are not necessarily correct! If anyone researches this, please post findings! Bob
 

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Discussion Starter #10
I finally got around to changing the oil again, and it was not the problem. it it still indicating low pressure at idle. I have never installed a pressure gauge before, and haven't had this tractor apart yet. Where exactly is the oil sending unit, and how do I install the gauge? Thanks in advance,

Jon
 

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why not check the compression? do you know the hours on this engine? follow AL's suggestion and look at the oil pressure relief valve.
 

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Jon, Looking at your dipstick, the oil sender should be above and to the left of the dipstick...maybe 1" round, sticking out maybe 2" and should have a wire on it (possibly tubing, but thinking a wire). Sending unit unscrews counterwise. Determine thread, probably 1/8 NPT and screw a gauge in with the same thread. Report back with both low rpm & max rpm pressure readings. Bob
 

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I'd like to add that pressure should be checked with your gauge at both low idle and fast idle (minimum and maximum RPM) and this should be done with the engine cold and again after it has warmed up to operating temperature. So basically, put the gauge on before running the engine (you can run it for a minute or so if you need to move the tractor outdoors, just don't let the engine warm up) and get your readings at low and high RPM, then let it warm up and take the readings again. And I'm sure I don't need to say this but, if pressure IS actually low, don't leave it running like that.

Oil changes viscosity as it warms up, so checking like this covers all possible circumstances... except for under heavy load, but you didn't seem to be working the tractor hard when the problem occurred.
 

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Discussion Starter #16
And the culprit is... oil pressure regulator valve. Two people in this thread suggested issues with it, and another site also mentioned it. I replaced the valve body kit (JD part #AM880983), which comes pre-assembled with everything from the valve body to the cap stake valve, EXCEPT the o-ring; the o-ring (JD part #MIU804787); and the housing gasket (JD part #M805699). Be careful scraping the gasket to avoid gouging the housing. Be sure to crack the retaining nut loose before you remove the housing. Overall, this was very easy to replace, and took less than an hour. Oil pressure has been restored at all RPM. I have attached a diagram.

Thanks for all your help.
 

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