Engine oil capacity of JD790?

[sixdogs]

My JD790 is supposed to take 4.3 quarts of engine oil but that amount goes way over the full line. The oil get drained when hot and I let it go for maybe 15 minutes to get as much out as possible. Filter change too. Still, I'm full at maybe 4 qts. So is the book wrong on the amount or the dipstick wrong?

 

[Henri88]

My JD790 is supposed to take 4.3 quarts of engine oil but that amount goes way over the full line. The oil get drained when hot and I let it go for maybe 15 minutes to get as much out as possible. Filter change too. Still, I'm full at maybe 4 qts. So is the book wrong on the amount or the dipstick wrong?

Have you started your engine for a few second after adding the oil, to fill your filter? Was not mention in your post.

 

[sixdogs]

Have you started your engine for a few second after adding the oil, to fill your filter? Was not mention in your post.

Yes I do.

 

[Henri88]

The manual does mention ''approximately 4.3 quarts''. It would not be the first time that a manual is not dead on. I don't know how much overfill you are, but for ease of mind, you could ask someone with a 790 to measure their dip-stick and compare. In the mean time, might not be a bad idea to bring the level down a bit.

 

[RoyJackson]

My JD790 is supposed to take 4.3 quarts of engine oil but that amount goes way over the full line. The oil get drained when hot and I let it go for maybe 15 minutes to get as much out as possible. Filter change too. Still, I'm full at maybe 4 qts. So is the book wrong on the amount or the dipstick wrong?

There were 3 engines used during the 790's production life...all Yanmar engines, but different. Are you sure you have the engine for your model (goes by tractor serial number, BTW)?
If 4 qts fills the sump, then that's what you want to use. Suggest you mark up your manual for future reference.
BTW, it's better to be a bit low (but still between the FULL/ADD marks) then too much oil.

 

[Henri88]

Should've read your profile before replying to your post. You are no newbie with tractors or engines.

 

[sixdogs]

There were 3 engines used during the 790's production life...all Yanmar engines, but different. Are you sure you have the engine for your model (goes by tractor serial number, BTW)?
If 4 qts fills the sump, then that's what you want to use. Suggest you mark up your manual for future reference.
BTW, it's better to be a bit low (but still between the FULL/ADD marks) then too much oil.

My sn is LV0790G69xxx and I show it as a 2003 from the sn range.
I bought this used from original owner, it only had 95 hours on it and is a cream puff.
I always try to get the oil right on the "full" line and it's OVER by maybe half the distance between full and add.
Never thought about it but suppose there are there different dippsticks?

 

[RoyJackson]

My sn is LV0790G69xxx and I show it as a 2003 from the sn range.
I bought this used from original owner, it only had 95 hours on it and is a cream puff.
I always try to get the oil right on the "full" line and it's OVER by maybe half the distance between full and add.
Never thought about it but suppose there are there different dippsticks?

I believe there were different dipsticks as well as different locations.
My 790 (when I had one) was also a 2003 build. The dipstick was definitely a PITA to get to!

 

[sixdogs]

I believe there were different dipsticks as well as different locations.
My 790 (when I had one) was also a 2003 build. The dipstick was definitely a PITA to get to!

Roy--you are spot on. I just looked up the parts at Deere and there are three different configurations, three different blocks and three different dipsticks. Me included for not even thinking of different blocks.
It's raining cats and dogs but when it's done I'll head out and find my PITA dipstick and try to figure out what I have. Not sure yet but I might not have the right dipstick but don't hold it to me just yet.

 

[sixdogs]

OK, I checked the serial number and confirmed I have the correct dipstick. So, here's a photo of what appears to be the correct dipstick with the oil showing how much over it is. Since the 790 only holds a little over 4 quarts I figure this is OK even though I know not to "overfill", even though I am not sure I am actually overfilling.

Reason for this is I have had and seen other Deere tractors with small Yanmar engines that were damaged by low oil. I saw a Deere 950HC that had low oil pressure and when we went through the diagnoses learned that the Yanmar engine in it had an oil flow system that would starve the main bearings first in an issue of low oil. Since onlyy 4 qts are in the thing, one quart low would to be an issue. And since the oil is is hard to check, guys don't do is so often

So I maybe I have what appears to be too much oil and maybe I don't. But snce the engine is a blueprinted mechanical manufactured item it would appear the correct amount of oil is as stated and correct. For whatever reason, the dipstick is reading wrong?
Any thoughts on this?

 

[RoyJackson]

So I maybe I have what appears to be too much oil and maybe I don't. But snce the engine is a blueprinted mechanical manufactured item it would appear the correct amount of oil is as stated and correct. For whatever reason, the dipstick is reading wrong?
Any thoughts on this?

I don't think you're reading it wrong. It most assuredly looks overfilled.

This is what I'm going to suggest:
Drain the oil out completely (let it set with the drain plug and filter off for at least 15-30 minutes). Handle the oil filter carefully since it's new and can be reused...I wouldn't reuse the oil...oil is cheap.
After that 15-30 minutes, re-install the oil filter. Then add 3 qts of oil...let set for 5 minutes or so, and check the level. Then add another 1/2 qt, recheck the level. If it's showing on the stick, start the engine long enough to flow the oil (a minute or two), shut the engine down and let it set 5 minutes...then recheck the dipstick. I'm going to guess the oil level will be low to half way up the stick. If so, I'd leave it there...or maybe add just a bit more (no more then 1/2 qt!).
Keep track of how much oil you are using...
Also, I can't recall if the oil filter is horizontal or vertical...I can't recall filling it before installation though.

I cannot recall the volume between the low and high marks of the dipstick...but I'm pretty sure it's not a full quart.

 

[Henri88]

It would seems that it holds closer to 4 quarts than 4,3 as mention in the manual, although the manual says ''approximately''. I would trust the dip stick before the manual. I personally would remove the oil filter and drain it and put it back on and see where that would bring me. As Roy mention, which ever way you decide to do this, I would not reused the oil.

 

[sixdogs]

I'll do what Roy suggested but I have to wait until March when it warms up and i can get the tractor out of the barn again. Stuff gets packed in a little tight and unless we get a warm spell, it's sleeping for a few months. Still, I can't see how there can be that much variation in capacity. I'm going to order a correct dipstick just in case the one I have came from something else. You never know.
I'll report back.

 

[sixdogs]

I couldn't wait until March and a sunny 55 degree day had me out in the barn today and I think I figured it out and learned something in the process. Roy got me thinking last night when he warned of overfilling oil so I looked into it and got out my owner's manual. In big print, as we have all seen is "DO NOT OVERFILL".
The problem, it seems, is that an overfilled crankcase can cause the crankshaft to drag in the oil and foam it enough to starve the main bearings for oil.
I took the 790 oil filter off--cold--and drained a very small of oil out. Just a small amount caused the overage in the dipstick to drop by nearly half of the overage. In other words, the excess was nowhere near as bad as feared and I suspect the configuration of the oil pan caused the oil to gain quickly on the dipstick once the full line was reached. Maybe, because overfilling is so bad for the engine, the maker made it this way to scare owners into not overfilling. Anyway, two dumps of a very small amount --1 1/2 to 2? ounces-of oil brought the oil back to the "full" mark. It now has probably 4.25 qts of oil in it and is correct.

Now, I have two other tractors I accidentally overfilled when filling from a 5 gallon bucket and the same thing happened. On my Kubota L4300 that holds 8 qts, it looked like I was a quart over based on the distance the line would be if I was a qt low. Just three dumps of very little cold oil from the filter got the dipstick back to the full line. The oil must be full exactly at the bottom of the crank and it must not take much additional oil to gain on the dipstick.
Same thing with 9 qts in my Deere 5520. It looked like I was a quart over and two dumps of that filter brougt the oil back to the fiull line. This filter held more oil but is was only a few ounces.
Anyway, that's my story and what I learned. At 63 years of age I thought --err...knew-- I had learned it all but that's what I discovered. All this seems perfectly logical in retrospect and maybe everyone knows but me but I do know I will never overfill my oil.

 

[Henri88]

Glad to hear it work out ok. I use that oil filter trick a few time and it work great, that's why I suggest it to you. Trying to remove just a small amount from the drain plug can be challenging and messy. :thumbsup:

 

[RoyJackson]

I'm glad you didn't wait until Spring (your original intention).
I'm guessing you drained about a 1/3rd to 1/2 a quart.

Good lesson to all, BTW...never fill the sump completely at first...leave it 1/2 to one quart down...top off if necessary.

 

[sixdogs]

I'm glad you didn't wait until Spring (your original intention).
I'm guessing you drained about a 1/3rd to 1/2 a quart.

Good lesson to all, BTW...never fill the sump completely at first...leave it 1/2 to one quart down...top off if necessary.

No-no-no, Roy. Just a couple to three ounces and that's max. Sure surprised me. I figure the crank fills up most of the space in the pan and just a little oil
raises the oil level on the dipstick a much greater amount than the pan space below the crank. The way I figure it has to be is that the max oil level is exactly at the bottom of the crankshaft and the reason overfilling oil is so dangerous is that it submerges the bottom of the crank. Which cause the oil to foam since the crank beats it and can starve the main bearings of oil.

This leads me to my earlier thoughtthat the reason my friend's Deere (Yanmar) engine main bearings went bad was maybe not because the oil level too low from neglect but maybe it was too high from an overfill of good intention? Maybe Yanmars are especially suceptable to overfilling? Anyway, Roy, thanks for alerting us to the dangers of an ooverfill oil situation and how dangerous it can be. Wow have I learned something.