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Discussion Starter #1
my 1998 JD445 temp gauge wanders up and down in the green, but on two widely separated occasions it has boiled over after mowing for an hour or so. I looked up thermostat on the JD parts list, but it indicates that it is discontinued. The nearest JD dealer is 100 miles away, so it is difficult to get info from them. The engine runs fine, there is no sign of water in the oil or oil in the coolant, and except for those two occasions the coolant level stays constant. Do I have a problem, or do I just need to check the coolant level more often? I have a full cab so it is all too easy to neglect to do so. :fing20:

Ron
 

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The Magnificent
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20,952 Posts
I'm wondering if you don't have another issue, Ron. What are your total hours on this machine? Last time a fluid flush and fill was conducted? Are you doing anything particularly stenuous when this happens? When were the valves last adjusted?

Also some of the more experienced guys are going to want your serial number, so I'll just ask for it now.

As for PM, I check my oil, hydro fluid (and would check my coolant if I had a water cooled machine) prior to each use.
 

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Discussion Starter #3
Thanks for the reply,

When the boil-overs occurred I was cutting some pretty tough grass and reeds, so it was working pretty hard, that could explain why it got so hot, although I have cut the same area many times and had no problem. The cooling system has never been flushed, but due to the boil-overs, the coolant has been pretty well replaced.

tractor sticker # is 26030-2193 AOO

engine is K series OHV FD620D
family ID is SKA617U5G2RA build date is 0397

454 hours

As I said, it runs great, never a problem starting or operating and no sign of unauthorized fluid interchange :D Perhaps a good flush is the answer and a few years overdue in any case.
 

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Diesel Power
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1,604 Posts
The only times my 445 overheated was when I was mowing taller grass and dust packed in the radiator screen and the screen below the dash. When you turn the tractor off, most of this falls off because it looses suction from the fan. When mowing tall, dry grass I keep an eye on the temp gauge and clean the screens if the needle starts to move.
 

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Discussion Starter #5
I hear you on the clippings buildup and watch that closely, and because of the cab, clippings also gather on both side screens, and at our altitude (6500 ft) I am down on power about one third as well. After each use I blow out the radiator and screens with compressed air. I wasn't very clear in my original post, my real question is about the temp gauge continually cycling up and down in the green as I mow or blow snow. It never stops, just slowly up and down from low green to about three quarters green. I suspect the thermostat, but according to JD, the thermostat listed in their parts list is no longer available. Or is this really a problem at all?
 

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This sound similar to the problem I had with my '97 445 this spring. Ended up being the gasket on the front of the motor had failed. There was no coolant in the oil, etc, etc, etc. Took it to the dealer and they replaced the gasket and water pump. While they were in there they also did the replacement of the plastic cam gear and the associated parts that go with it. Runs like a new tractor again! I didn't need to do all of that for this problem, but while they were there I had them do it.
 

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It doesn't appear that the thermostat has truly been discontinued, I found AM121668 and this link in a few minutes:

http://www.greenpartstore.com/John-Deere-THRMST-AM121668-M123434_p_6851.html

I am sure you can contact your local dealer.

I would suspect your water pump before your thermostat but would check both of them out closely (assuming the coolant level is proper and the radiator is clear).

Regards,

Rich
 

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Experienced User
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I never had overheating issues with the 445 that I had. This is what I would do in this order.
If you have not blown out the raidator fins, you should do that. I found the screen did not catch everything and you can get dust buildup at the bottom of the raidator.
Check all the hoses to make sure there are not bends that would restrict coolant flow. Check your fan belt to make sure it is not slipping.
Replacing the thermostat would also be on my list. You should be able to fine a place online that sells that part. To prove if that is the issue, you could take it out and try running it to see if the condition changes. I would not recommend leaving it out because the engine needs to be temp controlled otherwise you could have bigger issues over time with valves, carbon, etc.
You might also want to flush the cooling system given the age. You could buy an automotive coolant system flush and use it. You put in in the radiator, run the engine for a few minutes and them drain everything, run a plain water rinse, and refill with new antifreeze and water mixture.
If that does not do it, I would then dig into the engine water pump. A worn impeller or a blocked port would be the next possibilities.
 

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Discussion Starter #9
Thanks, found the thermostat & gasket, and ordered the sensor too, just in case, if that doesn't do it, I'll try the water pump.
 
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