jd 850 3cyl

[msg]

my neibor has a 85 jd 850 with the yanmar 3 cyl. it just started seeping oil at the head gasket, getting harder to start, and wont idle. has 682 hrs and been maintained by dealer. what should he do? is this a problem? how hard is this motor to overhaul? did not overheat and has not been run low on oil but his wife does mow with this. any help is appreciated!!!

 

[RoyJackson]

If it's leaking at the head gasket, it's not holding compression (hence, the hard starting and inability to idle).
As to why the gasket blew..well, you said it hasn't overheated. Are you sure?

Nevertheless, I'd pull the head off and take it to the dealer or a machine shop. The machine shop can tell you if the head is warped. If not, put a new gasket on it and torque it properly!!!. You'll have to re-torque after so many hours (you really need the shop manual for this). If you don't know what proper torque technique is, let the dealer do the job.

If the head is warped, you may have to strip the head down to a bare casting (leave the valve seats in though). The machine shop can mill it flat for you. You want the minimum amount of material taken off..or whatever the shop manual requires. There may be thicker gaskets available to account for the material removed from the head (if it comes to that). This is to maintain the correct compression ratio.

By the way, when you pull the head off, look for cracks around the head and block. If you seeing oil, the crack may have started at one of the oil passages. Cracked heads can be welded, but if it is cracked (and I hope it isn't!!!), you might want to start looking around for replacement parts. If the block is cracked (unlikely as it is)...that's beyond my realm of expertise.

 

[msg]

thanks,roy. ill tell him, the coolant overflow and radiator are full so i dont think it overheated , BUT when she was driving anything could have happened, the dash just has idiot lights and she swore she never saw anything. this just happened recently and she said it just started running bad after mowing for a time. could this have happened over a period of time?

 

[DK35vince]

msg,
I put a tempature guage on my 850 for under $30.
When field mowing my screen and radiator would plug quite often and the temp light would come on. But by then you are already overheated.
Parts stores or Wal-Mart have temp guage kits(cheap).
I used a hole saw and drilled the right side of the dash panel (near the light switch) for the guage.
Roy is right ,it sounds like the head gasket.
You could have a compression check done before tear down to get a better idea !

 

[ScottAR]

Check for grass buildup on the grills and on the radiator screen... It really sounds like it overheated. My 1050 got hot enough to trip the light once from dead grass fluff on the radiator screen. I shut it down, cleaned it off and went to lunch to let it cool a bit.

 

[msg]

we already know compression is down cause its hard to start, looks like we'll have to yank the head. thanks!

 

[DUMBDOG]

When I mow, I have to stop and clean the grill off every half hour or so because of the cottonwood trees, they have all kinds of fluff in the air that clogs of the front of the tractor, I just watch the heat gauge and when it goes up to the top of the heat range, it is time to stop and clean the grill, the heat gauge goes down right of way then.

 

[ScottAR]

Unfortunately, The 1050 only has a light. About 1-2hrs. (every water break I guess) I stop, clean the outer grills off, and take a peek at the radiator screen. Not a big hassle. I've found a long bristle, old car washing brush to be a great gadget for cleaning the grills.

 

[BATTY54]

reading the thread and had a Quick question what do you use for the sending unit on the 850 are they metric?

 

[BB_TX]

The 850 is Japanese made. I think you will find everything on it is metric. At least everything I have found on my 950 is.