john deere 620 problems

[Anonymous-0]

I own a 620 john deere (nothing but the best). Its a long story. It goes like this- I paid $5000 for this thing, runs nice, got it home didnt run any more, blew smoke out the muffler, I came to find out there was some kind of nest in the air cleaner, caused it to suck oil out of the pan. Fixed that, got some one to look at tractor, fixed couple of things (3pt arms, tuned engine, tuned hydraulics, etc) - cost 1500, so here i am with a tractor that is now worth $6500. Well later in plowing season i noticed it smoking a little out of the breather when it worked hard. It got worse over time. I got on it last week and warmed it up, smoked a little, i was on the road coming up a hill and i idled it down cause i like to idle it down and then throttle it up to hear it work, well when i idled it down it looked like i had just been burning a 50 gallon drum of oil, it was nasty, oil burning horrible out of the breather. but when i throttled it up it stopped smoking. It doesnt use too much oil but a little. What could be wrong with this???? im getting sick of spending money on this thing. Any suggestion appreciated. thanks- Caleb

 

[RobMD]

First of all, you paid too much for that thing. Sounds like a restoration in a bottle, a.k.a. marvel mystery oil.... howeverrrrrr.. You say it doesn't use too much oil, so first I would suspect your crankcase ventilation pump to be bad.

 

[Anonymous-0]

really? Cause i was thinking valves seeing as the breather pipe runs from the valve covers.

 

[Allan in NE]

I'd weld the spiders. :>)

Allan

 

[Anonymous-0]

HaHa very funny.

 

[RobMD]

yeah, i'm mixed up, yeah, my suggestion doesn't work. It probably is the valves.

 

[fixerupper]

Worn valve guides will cause it to smoke out the muffler when the throttle is pulled back. Worn compression rings will cause crankcase pressure and blowby. Sometimes the compression rings can be leaking compression but the oil rings will still be good enough to keep the oil consumption down to an acceptable level.

I had a tractor that had a fair amount of blowby at idle but no blowby under a load. I was told by a mechanic that when it was loaded the increased combustion pressure would force the compression rings out against the cylinder walls and help them to seal better. Jim

 

[Anonymous-0]

Probably both worn valve guides and worn piston rings. When you throttle back it closes the throttle plate and causes higher intake vacuum and pulls oil up past the rings indicating worn rings. Also when you throttle up it would have higher cylinder pressure causing more blowby past the piston rings which would come out the breather. Yep an overhaul is in it's future. If ya like the tractor fix it and enjoy it. Still cheaper than a new one.

 

[Anonymous-0]

I think Allan is a bit cranky, or happy and laughing at this john deere.

 

[Mike M]

From what I have seen on those 20 and 30 series 2 cyl. it would not suprize me one bit to open it up and find the top piston rings either severly worn and have alot of groove side play and/or be BROKEN into pieces. If you plan on doing much hard work like plowing you should continue to see it get worse as time goes on.