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Big Mac
03-30-2008, 09:52 PM
Well, this one has really got me going! My John Deere 750 is almost 20 years old, never had this problem in the past. When it is started cold, it takes about 10 to 15 seconds for oil pressure to develop. I thought it was the idiot light, but I put an oil pressure gauge tester on and it told the true story. When it does get pressure, it is 25 psi at 1000 rpm. When warmed up, it has pressure at start up. All the time I have had this tractor, the oil light would go off just after start up, until a couple of days ago, now each time I start it to test something it seems to take longer to get pressure.
Any helpful advise would be really appreciated!
Big Mac

Archdean
03-30-2008, 10:32 PM
"I put an oil pressure gauge tester on and it told the true story." AND What did it tell you? You don't say!
The line to the gauge should of been pre filled to get a true reading as air compresses and oil does not!


When was the Filter changed and the screens cleaned?
What Weight oil and how long has it been since it was changed and the outside temperature when problem started?
Regardless how old the machine is, the important thing to know is the approx # of hours! (How Many?)Please be more specific and then I can give you a much better answer!

Big Mac
03-31-2008, 12:13 AM
Thanks for your reply.
The filter and oil (30 weight ) were changed 6 hrs ago, same oil and filter I have used every year. There are no filter screens that I know of or are any mentioned in the service manual. As to the temperature, that has never been a problem, as I used the tractor to get my wood to the house, about twice a week. There are 1907 hrs. on the engine, and it is a yanmar three cylinder.

I was told maybe it could be a by pass valve inside the filter housing, any thoughts on that?

Big Mac
03-31-2008, 12:47 AM
The oil line was full of oil. The tester gauge reads 25 psi when the engine is warm. I let it set with the gauge still hooked up, and the next day (engine cold), the engine ran with 0 psi for 10 to 12 seconds when first started, then the gauge jumped to 40 psi, till the engine warmed and the psi returned to 25.

Archdean
03-31-2008, 01:50 AM
I believe you were told correctly about the bypass valve, that is why I asked about the oil & etc. it appears that it is sticking and you can almost with certainty rule out the oil pump since you eventually develop normal pressure!!

One other thing have you recently changed or used a different style/brand/model Filter? Just to rule that in or out!

PaulChristenson
03-31-2008, 02:11 AM
Well for the record...JD recommends
Plus-50 SAE 15W-40 -- Air Temp from -15C to 50C or
TORQ-GARD SUPREME SAE 5W-30 --Air Temp from -30C to 30C
as the preferred oils

You can use
TORQ-GARD SUPREME SAE 30 -- Air Temp from 0C to 50C

If you are using non JD oils, then they must meet
API Service Classification CF-4 or CF or higher

Just out of curiosity...you didn't happen to use gasoline engine oil did you?

Since you changed the oil 6 engine hours ago...You are aware that JD approved oil filters have a bypass valve built in...

Diagnostic Malfunctions for JD Agricultural tractors...(don't know if Yanmar fits in this catagory...:rolleyes:

LOW OIL PRESSURE
1.Oil pressure regulating valve failure
2.Excessive clearance between oil pump gears and cover
3.Clogged oil pump screen<<<Note: NOT the oil filter
4.Excessive bearing clearance
5.Low oil level
6.Improper oil

Big Mac
04-01-2008, 01:16 PM
:wink: :wave: Hey, you guys are Great!!

Many thanks to Archdean and Paul Christenson!
Paul hit the nail on the head when he asked about the type of oil I had used in my recent oil change. I no longer had the containers, but the question was there, was it a gasoline engine oil? I had checked most every thing else, so I changed oil again useing Torq Gard Supreme Sae 30. The results were quicker pressure and a higher oil pressure when warmed up.
Now, my question is do you think I have caused any engine damage useing the wrong oil? I ran it less than 7 engine hours after the wrong oil was used. It seems to run the same, no louder, same power, and no funny engine noises. The only difference was the slow rise to getting oil pressure.
Again many thanks to the guys on Tractor Talk. Some times you can't see the forest, for the trees. It helps to get some advise from someone looking over your shoulder.

Chum

Archdean
04-01-2008, 02:22 PM
No! I wouldn't think that you hurt anything as what you saw of course was a thicker oil taking longer to energize your light/gauge but the pressure was already there to the bearings!

As Paul says it pays to use the manufactures recommendations even though you don't use their brand!!

PaulChristenson
04-01-2008, 03:27 PM
No! I wouldn't think that you hurt anything as what you saw of course was a thicker oil taking longer to energize your light/gauge but the pressure was already there to the bearings!

As Paul says it pays to use the manufactures recommendations even though you don't use their brand!!

Ditto Archdean...but PLEASE USE JD products...it supports my JD stock dividends...:rolleyes: :D

jd110
04-13-2008, 06:36 PM
Just out of curiosity. Did you change the filter again also? I once had a similar problem on a Ford car with a 302. I had installed a Lee or a Fram filter and had similar symptoms until I installed a Motorcraft filter. Problem was solved.

Big Mac
04-14-2008, 01:36 PM
jd110, to answer your question, yes I did change the filter. I didn't know if the old oil in the old filter, would cause a problem with the new oil. At that point I didn't want to take a chance on any variables changing the test. I did use the same type of filter I had removed. Same type I have been using all along.:tiphat:

Doc
04-14-2008, 04:12 PM
I've used synthetic in my old truck to make things easier on the old girl. Worked great. I was warned of the syn maybe finding small crevices and causing a leak where I didn't have one before, but that did not happen. The engine runs cooler due to less friction. Seems like a win win to me. Syn also hangs onto enjine parts longer which also prevents engine wear and tear at startup. Sure worth a try.