JD 790 Sked Maintenance - Replace Thermostat??

[sriddle1ny]

I finishing-up doing all the maintenance (fluids/Filters, etc) on a used '04 JD790 I picked up mid september and then I noticed (ooooppppsss) "Replace Thermostat" in the Operator's Manual every 2 years or 2,000 hours. The Thermostat and Gasket are even listed on JD's handy-dandy 790 Quick Reference Guide as scheduled maintenance replacement parts.

I picked up the Tractor in OK and getting it ready for the very cold MN Winter, last task, just installed the Block Heater and two weeks ago the 3 retro mounting kits for the new Front Mount 59" JD Blower.

Question: Is there a way to test the Thermostat or tell if replacement is needed, there's no record of it being replaced. Also, anything I should look out for, replacement tips, etc....... The used 790 had 332 hours on it. THANKS........

 

[greg_g]

Sure, you can test it with a thermometer in a pan of water on the stove. But thermostats are relatively inexpensive. If you're contemplating removing it for testing, why not just toss it on general principle - and slap in a new one? Either way you go, you're still likely going to have to buy a new thermostat housing gasket.

//greg//

 

[Tractor Pilot]

sriddle1ny,

Your manual says every 2 years or 2000 hours - that is an estimated average use of 1000 hours per year. So far your tractor has averaged 50 hours per year. If it were me, I would wait until 1000 hours. But for piece of mind, it can be replaced for about $30 (DIY). However, any thermostat can fail at any time. Just keep an eye on the temperature gauge.

My manual for my JD770 says to replace the thermostat "as needed." As far as a test - warm up the motor and look where the needle falls on the temperature gauge. Mine is in the middle of the green arc. You can also remove the radiator cap (before you warm up the motor) and check to see that you have no circulation of the coolant when the engine is cold and circulation after the thermostat opens when the engine reaches temp.

I know MN can get really cold. You might want to also consider installing a hydraulic oil heater. JD makes one for my JD770 (AR94493; AR95434), but I don't see it listed for the JD790. Since these two tractors are so similiar, it may work with yours.

Do you already own the JD59 snowblower? If not, there is a guy by me who is selling one used on craigslist for $2500: JD 59" Snowblower
I don't know what they go for new, so not sure if that is a good price considering you would have to get it from CO to MN.

Bruce

 

[grsthegreat]

YEIKS..... i had my JD870 for 14 years and never replaced the thermostat. I only accumulated about 1400 hours on it though

 

[sriddle1ny]

Tractor Pilot, Thanks and that's the kind of insight/info I was looking for........

grsthegreat, I just thought it was odd that JD Scheduled Maintenance specified the interval for replacement, makes me wonder about thermostat reliability when "2 years" is cited.

Since the Tractor is from OK not sure if the thermostat was even removed so Tractor Pilot for that amount and since I just learned how to do all the maintanance why not. Regarding the snowblower I purchased a new bare bones JD59 and it cost $3,423.44 w/MN sales tax included. I remember seeing snowblowers out there > $3,500 but I guess if you don't have to purchase the (3) Retro Mounting Hardware Kits then you're ahead of the game since I just spent $1,817.13 for all three kits. I'll look into the hydraullic oil heater since we do quite often go down to -22 and boy does the air coming down from Canada blow too making for white-out conditions with little as three inches of snow........

 

[Tractor Pilot]

I just picked up a used Buhler/Allied 60" snowblower off craigslist. Can't wait for it to snow again!

 

[grsthegreat]

I just picked up a used Buhler/Allied 60" snowblower off craigslist. Can't wait for it to snow again!

Nice blower. I had a farmking 60 inch blower for years..also made by Buhler. The only problem i had with mine was the center flighting always bent (i have lots of rocks early season). I solved this by welding on a support tab. I wish i did it before they bent for the 3rd or forth time, as the overall look of the auger would have been better.

 

[JDGreenGrass]

I just picked up a used Buhler/Allied 60" snowblower off craigslist. Can't wait for it to snow again!

You'll love that set up. Looks almost as nice as my 770.

 

[sriddle1ny]

You might want to also consider installing a hydraulic oil heater. JD makes one for my JD770 (AR94493; AR95434), but I don't see it listed for the JD790. Since these two tractors are so similiar, it may work with yours.

Tractor Pilot, Just looked at the Transmission Housing Illustrated Parts Breakdown for both the 770 & 790 in the JD Parts Catalog with their Transmission Strainer, Cover, etc. = same Part Numbers so I'm with you, wonder why they don't call out the Transmission Oil Heater for the 790. I'll check with my JD Dealer this morning when I pick-up the Thermostat. One question for you, where did you mount the hanging cord, I see the tie band and wonder about interference with high snow, etc., can you attach a PIC in your response...

I'll need all the heat I can get with the fluids at -20F, everyone says this year is going to be worse than last year and I had many 6' drifts that my old (and sold) JD3010 with its McKee Blower went right through, I'm afraid my new/used 790 CUT with its JD59 might pose a challenge so my neighbor with his Farm Tractor and 3-Pt rear blower is ready & willing to help me out....... We're planning on moving in the next year or so so I wanted to downsize the tractor, we'l see how it goes this year.......

 

[Tractor Pilot]

I don't have the hydraulic oil heater on my JD770. Still trying to decide if I want to install it. The winters where I'm at in CO are not as cold as MN (-10F and colder is rare). When it does get down near zero and colder, I just put the hydraulics into relief for about 5 minutes to warm up the hydraulic fluid.

Check out this thread: http://www.tractorbynet.com/forums/john-deere-owning-operating/29211-block-heater-jd990.html
Johnbilt has several pictures of his hydraulic oil heater install on his JD990 (including how he secured his cord). Should give you an idea.

 

[sriddle1ny]

Tractor Pilot, Understand & sorry that I misinterpreted your suggestion. After talking to the local JD Dealer they basically said the Hygard - Hydraulic Low Viscosity Transmission Fluid & associated filters that I recently replaced is rated for air Temps -40F to 86F. They indicated that they haven't installed a Transmission Oil Heaters in any of the JD CUTs they've sold to date and since I have the tractor stored inside out of the wind + a block heater that will be on an hour or two before doing any work they didn't find it crutial that I install one. Perhaps some out there reading this may suggets a different outsome..............

 

[Tractor Pilot]

My JD770 manual recommends JD low viscosity Hy-Gard and to use a block heater and hydraulic oil heater if operating the tractor in temps below -15F.

The coldest I ever started my tractor here in Colorado was -10F (although it was -25F the night before and that really cold soaked the tractor). And even with the low viscosity Hy-Gard, the hydraulics sounded really, really cold when I first fired up the tractor.

I called the local JD dealer after that really cold day and asked about the hydraulic heater. He told me that he had sold some hydraulic oil heaters, but it was rare. So far, my tractor has survived 14 winters here in Colorado without the hydraulic oil heater. If I moved to MN, I would probably install one.

As far as the JD dealer advise, you have to keep in mind that many people preheat their hydraulics with heaters other than the JD one.

 

[mfreund]

Wow, that 3010 was GORGEOUS!!!!

 

[RoyJackson]

Wow, that 3010 was GORGEOUS!!!!

Yeah it was!!!!

 

[sriddle1ny]

mfreund,

THANKS........... Yes it was a very nice '63 3010 tractor but it was time for a replacement since I'll be moving on in the next couple of years to a smaller lot. I invested about 11.5 K into that machine over the 6 years I owned it. It's amazing what a sand blast, prime and professionally applied DuPont Imron paint can do to an old tractor and a used '72 Cozy Cab I found several years ago. My neighbor who is a master mechanic and a lifelong farmer maintained it and fitted the Cozy Cab as trade for using tillable lands I own. Here are a couple of transformation shots??. before and after. :thumbsup:

 

[Henri88]

What an amazing transformation! Sweet! :thumbsup: