I may have to replace the head gasket in a 8640. It has low hours on a rebuild but is leaking a little water on the out side i havent seen it yet. If i cant find a manual is there some one hear that can tell me torque on head bolts, how to set the valves and any thing that i may need to do special?
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8640 jd
- Thread starter Old Doug
- Start date
wrangler
Active Member
The engines in these tractors often had head gasket problems because the engine is part of the frame of the tractor. It causes the engine to twist over time and is much worse if the tractor has a dozer blade on it. Be sure to get the head and block checked for flatness or it will not seal in the long run. I have the John Deere technical manual for a 8630 that used the same engine. Head bolts were tightened to 140 to 160 ft-lbs then 175 to 180 and after break in to 205-215 ft-lbs. Valve clearance intake .013 to .017 and .023 to .027 in on exhaust. Liner height on used block .000 to .004 in.
wrangler
Active Member
You may be thinking of the V8 motor in the 8850 tractor. It did not stand up well in the ag tractor but in the John Deere pay loader it ran untouched for many thousands of hours. Many of the 8430 8630 8440 8640 8450 8650 8850 have had head gasket issues. They are costly to fix because of the labor to do a clutch job you have to disassemble so much of the tractor.
BuMach
Well-Known Member
i tought these big JD engines Always leak water at the gaskets..
have seen a lot off leaking JD engines (8, 10, 13 ltrs) in forage harvesters and a lot of them have leaking head gaskets that are sweating to the outside.
I would suggest to buy a service manual (they are not that expensive on a dvd straight from JD) or just check the web, there might be a few around.
and this manual will coverage the whole tractor so might come in handy when you'll have something else with the JD.
set the valve a bit loser (0,05mm) then suggested, and then reset them after 50hours (if its easy to get to the valves) this way you'll know you didn't tightened the valves to much when the head gasket get compressed the first hours.
It's quite the work but nice to do:thumbsup
good luck
have seen a lot off leaking JD engines (8, 10, 13 ltrs) in forage harvesters and a lot of them have leaking head gaskets that are sweating to the outside.
I would suggest to buy a service manual (they are not that expensive on a dvd straight from JD) or just check the web, there might be a few around.
and this manual will coverage the whole tractor so might come in handy when you'll have something else with the JD.
set the valve a bit loser (0,05mm) then suggested, and then reset them after 50hours (if its easy to get to the valves) this way you'll know you didn't tightened the valves to much when the head gasket get compressed the first hours.
It's quite the work but nice to do:thumbsup
good luck
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Andrew_D
Senior Member
8640.... ah, the memories!
We had a hail storm go through and flatten some of the wheat about mid-late July 1987?ish. Hail insurance wrote it off, but what to do with it? This was back when RoundUp was still north of $20/L and very few high sprayers around - almost all were tow-behind sprayers. Only option was to disc it under. Dad decided the time was right to get me into the "big" tractor. I thought I was in heaven pulling a 12' Rome disc at 3mph around that field. Then 2-3 weeks later, went over it again at an angle. Month after that, everything had rotten enough that we could get a chisel plow through.
One day, Dad went out to start it and the dampener fell off when he hit the starter. Closer inspection showed that the crank had sheared between the dampener and the front bearing. Dealer tore it apart for estimate and repair. Dad ended up trading it before the repairs were done on a JD 8760.
Andrew
We had a hail storm go through and flatten some of the wheat about mid-late July 1987?ish. Hail insurance wrote it off, but what to do with it? This was back when RoundUp was still north of $20/L and very few high sprayers around - almost all were tow-behind sprayers. Only option was to disc it under. Dad decided the time was right to get me into the "big" tractor. I thought I was in heaven pulling a 12' Rome disc at 3mph around that field. Then 2-3 weeks later, went over it again at an angle. Month after that, everything had rotten enough that we could get a chisel plow through.
One day, Dad went out to start it and the dampener fell off when he hit the starter. Closer inspection showed that the crank had sheared between the dampener and the front bearing. Dealer tore it apart for estimate and repair. Dad ended up trading it before the repairs were done on a JD 8760.
Andrew
I pulled the head its at the shop geting checked out. I didnt real see any thing wrong but when i lifted the head up the gasket tore into several pieces. I dont have the gaskets yet but i was thinking about puting some kind of sealer on it around the water holes maybe copper coat or something. I took the injecters to a guy that does most of the work on the owners tractors i thought it was funny that they were haveing me work on this on until he told me he wouldnt touch it. When i ordered the parts i talked to a JD parts guy that i know real good he about lost it when i told him i was working on a 8640.
Shimmy1
Senior Member
I was always taught that head gaskets are put together dry. I like to use these http://www.homelectrical.com/2-gree...18730.1.html?gclid=CKLO7M3KrMsCFQyNaQodxpMO8g on a die grinder to clean up the block. Some guys are paranoid they remove metal, I feel if you're using it that hard you shouldn't be working on an engine that deep anyway. You're probably already planning on it, but if not, tapping the head-bolt holes out is a must in my opinion.
BuMach
Well-Known Member
if i want to use something i sometimes use Loctite 3020. it's a spray that will help keeping the gasket on its place.
and helps seal it a bit too.
the old gasket probely leaked somewhere between the gasket layers.
and helps seal it a bit too.
the old gasket probely leaked somewhere between the gasket layers.
I have been useing the 2" pads on a right angle die grinder. I got to work in a engine machine shop for a week when i went to votec. They used a very coarse sanding disc i read some were it would give the gasket bite. The only thing that i worry about is geting abbrasive stuff in the engine.
I got the gaskets today. I word of advice remove every thing from the gasket boxes but the headgasket them slide the gasket from the box on to the block its to thin to handle other wise. I had the shop door open when i was checking out the headgasket to see if it was the right one and thought the breeze mite fold it up,
Shimmy1
Senior Member
Yep. Also, I will not touch a head gasket with my bare hands. Latex/nitrile gloves, or like OD says keep it on the box and a clean towel in your hand to push it on. No reason to chance a bit of oil on your skin getting on the clean gasket. OD, do you wipe the deck and head off at least a couple times with brake cleaner before final assembly?
Most of the time i use paint thiner or acetone. I worked at a shop years ago that rebuilt engines there was a shop a block away that did the same thing one day a guy that worked there in the office came by and ask if i would put a engine together for his boat. I ask him why he didnt have his shop do it he said i was alot cleaner.
Bad news they were about finished planting and they think it spun a bearing i havent looked at it yet.I work there by the hour and the pay is ok but they gave me a bonus check for some resone when i got it runing i didnt want it because i didnt fill good about the tractor after all i was told. I held the check and told my self i would cash it if it made it through planting.
d9gdon
Senior Member
Doug, it might have had a dose of antifreeze in the engine oil from the head gasket leaking if it was leaking to the oil and not just compression. Antifreeze and engine bearing surfaces don't get along for very long. Just a thought.
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Shimmy1
Senior Member
Why should you be worried if all you did was change head gasket?? You never had the pan off, did you?
I drained the oil after i removed the head and didnt see any antifreeze. No i didnt have the pan off but i just felt bad about it haveing a problem. I heared today that it was hauled some were to be looked at . I was glad i wasnt ask to work on it agin because there is already more work to do than i will have time for this summer. Its may not even be a bearing now some one thinks it could be the clutch ???? Some days its no fun being a mechanic.