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Discussion Starter · #1 ·
I have a John Deere 425, with a 20 horse Kawasaki water cooled engine. The thermostat was changed to a warmer one due to the EPA a number of years back, subsequent to my unit. The older, cooler 'stat is not available from Deere, and I have been unable to find an appropriate unit to replace my thermostat. The current Kawasaki part is 49054-2056, same as they put in a mule. It is an 82c thermostat. Can anyone suggest a source for a cooler thermostat that will fit this application? I've been to auto parts stores, a Kawasaki dealer, two small engine shops, and called Kawasaki customer service. The auto parts store had a picture book of available 'stats, but they were all larger than the Kawasaki part. The Kawasaki shop has a mule thermostat, which is identical, but also 82c.
This tractor has about 860 hours, and runs great until it gets warm. The temp gauge gets about halfway into the green zone, and it coughs and belches black smoke every time it hits a bump. It barely runs if the PTO is turned off, just getting too much fuel, it seems. Runs like a watch until it gets warm.
I'm not sure if the thermostat is not opening properly, or if it might have been changed out by the dealer in tha past. I bought this unit new. It seems to me that flushing the cooling system and changing the thermostat would be a good place to start. The air cleaner has been changed, and I just did an oil change. The oil looked fine, no look of coolant getting into it. The radiator is full, and the fluid looks an appropriate bright green. Oddly, the radiator reservoir has always emptied itself, but the rad always stays full. It's done that since it was new.
I could just try pulling the thermostat and running without, but I blow snow with this unit in the winter, and I don't think that would work too well.
 

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Are you running the original thermostat or a replacement? If the original at a minimum take the tstat out and check it in a pot of hot water with a thermometer to see at what temperatures it is opening and closing.

I have heard the same thing about the EPA deal, others have said the only way to use the new style thermostat is to also use the new carburetor – sounds expensive. Just today I saw that there was a guy over on weekend freedom parting out an older 425, you might want to contact him and see what he has, one used obsolete thermostat might do the trick. Coincidently I have been emailing him on some other parts.
 

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mvick,

Glad you found yourself here! :Welcome1: Hopefully some of our mechanics here can steer you to a solution (this is the same situation I had with my 425, where the dealer was able to locate the updated carb which made the tractor run again -- though never as well as the OEM configuration). If there is a lower temp thermostat available, I would recommend going that route first. :)
 

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running w/o the thermostat may not work either. The flow is designed with the thermostat in place.
 

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Don't pull the t-stat, as the engine will overheat. The water won't stay in the radiator long enough to cool.

Your symptoms don't sound like overheating. It sounds more like like vapor locking. If it wasn't bump related, I'd suggest a failing ignition delay module. A faling IDM gives very similar symptoms due to a weak spark not being able to fully ignite the fuel.

The t-stat change was to help with plug fouling, mainly on the Gators (that share the same engine). Raising the engine temp from 180 to 195 shouldn't make that much difference.

It's pretty normal for the overflow bottle to be empty. I'm not sure why either, but as long as the rad is full you are OK.
 

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Raising the engine temp from 180 to 195 shouldn't make that much difference
Engine Tech, the thermostat change on my 425 made a HUGE difference. To give some background, my 425 ran beautifully for ~ 500 hrs until the thermostat went. Up until that time, the temperature gauge did not cycle and the tractor always ran at the bottom end of the green. When the thermostat went, Deere no longer made the 160F stat and was substituting the 180F model. After installing the new thermostat, the tractor ran much hotter on the gauge and would cycle up and down (staying in the green but barely). However, the tractor ran like crap. It had nowhere the power and was very difficult to restart when hot. And on top of it all, the best feature of this tractor -- the cool operating platform to the operator -- was gone. I complained to my dealer and he did some research learning that Deere had changed the thermostat temp for EPA reasons and that there was an upgraded carburetor for retrofits. My dealer ended up finding one of these carburetors and installed it, and though the tractor did run much better, it never ran as well as the OEM configuration and was one of the reasons I purchased the 2210. I have already been in touch with Marty and my recommendation was to locate either a leftover 160F thermostat, or find an aftermarket one that fits. I encouraged him to post here and see if any of our posters can help. :)
 

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Thanks for filling me in JDFANATIC. I had forgotten what the original temps were. That is a quite a bit of difference. I used to know some of this like the back of my hand, but I've gotten a little rusty. :thanku:

A t-stat for a small car might work, but few are so cold. I agree, finding one from an old engine might be the best bet.
 

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Discussion Starter · #8 ·
Thanks for the help, guys. I haven't been able to locate a cooler thermostat. I have one shot left, a non-current Kawasaki number, new old stock, that my local Kawasaki dealer has located. I won't know if it is cooler until I spend the twenty bucks and have it in hand, but it's worth a shot. This may be the year I update to a 729, but I' like a beagle with a bone on this. I hate being defeated by such a trivial thing as a thermostat!

I got the original JD number from a dealer in Michigan who still has the old fiche. It is AM 109396 if anyone cares. All the computer systems do now is tell you what the part has ben superceded by.
 

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I know this has been a while since anybody has posted on this topic, but was wondering if anyone has come up with a replacement thermostat that will work in place of the old one? And what year if any did they change the carb to perform with the new thermostat? I have found quite a few thermostats that open at 160*, but haven't pulled mine out to get a look at it to see if I can match one up. Does anyone have the dimension of the one that go in the 425, 445.?
 

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I have 3 425 tractors.. 3 years ago one started over heating.. Here are the facts.. I pulled the thermastat, It was stuck in the closed position. OK I went to the John Deere dealer asked for one. Well when he gave me the Bill of near $35.00 I just said thanks and left it there.the tractor Has had over 500 hours put on it without a thermestat. It runs perfect Comes to about 130 degrees. No problem. Side note. On my 1960 Plymouth. 385 wedge 2 4 barrel afb Carters. I ran it over 100,000 miles No water pump No fan. No thermastat.It was fast;;; No overheating unless stopped at a traffic light ,or by a police man;;
 

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I'll attach the thermostat make and number referenced by bvp2000 in the other post for reference: it's an Autozone part # 7203-160 which is a 160 degree thermostat. Thanks for the reminder. :)
 

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I put the autozone one in a 445 that I rebuilt a year or so ago.....it is still running great. Sorry I didn't post the part # before..was in a hurry.
Thanks JD for posting it.
 

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Tony,, If you are running your 60 Plymount without a Water Pump, How is it being cooled?? Or are you running it at the Drag Srip??

I think the Old IH Cubs ran without a Water Pump, but never understood how they kept the water circulating through the radiator...
 

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I think the Old IH Cubs ran without a Water Pump, but never understood how they kept the water circulating through the radiator...
Via thermosiphoning. Basically like how hot air rides and cold air sinks, the same happens in the engine. Many of the earlier 2-cylinder JD's didn't have a water pump either. Not until the horsepower outputs rose did they start getting pumps.

http://en.wikipedia.org/wiki/Thermosiphon
 

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The combustion engine is not a new thing.. . All your early tractors cars did not have a water pump on them. also NO thermostat With out a water pump the engine will run at near 200 degrees, which is were it likes to run at;; 212 boiling point is increased by 3 degrees with every Pound of pressure on the cap ; hens 15 pound pressure cap pushes the boiling point To 227 degrees; It is most important to remember Your regular engine oil brakes down at 235 degrees. And there is NO cooling in the Crank area. It's only in the Cylender area;; WE in our shop done oil testing For over 20 years. . The heat in the engine is because of tollerances and clarences that change With heat. Altho there is a tiney bit of Horse power gained By running it hotter; That is the reason for the inter cooler on a tubro;. Like I stated in my prior post NO fan NO water Pump NO thermostat While driveing NO over heating; Only when stopped , I would kill the engine.. Any one who doughts this. I must put this question to you.. I service owan engines some with over 4000 hours on the Clock.. OH MY > they are air cooled. NO thermastat. They run in 20 below F and at over 110 above F; Just think about that..
 

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This is an interesting post;; Well yesterday I was having a talk With some older gentalmen. the subject come up. And the importance of haveing the proper temp on an engine. His responce was quite simple. If she has the proper oil and she fires It's good to go. . The B17 made many bombing runs . helped win WW2 and It had a radial Engine.. Supprise NO thermastet NO rad; I found that interesting, Only a small oil cooling.. So i say Don't get to hung up on the modern tech;
 

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I too bought the thermostat from Autozone after reading the orig. thread about $20 with tax not cheap but still a lot better than the Deere price. Thank's to Jwill and bvp for the great head's up on that one. Alway's nice when the solution is simple having to go for a different carb over something like a thermostat is ridiculous especially when the tractor ran good to begin with. BILL
 

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OK from what I have been able to find out this thermostat 7203-160 that can be had at Auto Zone has some others that cross reference to it. Hypertech 1003 that can be had at Advanced Auto, Amazon, Summitracing and others and Valucraft 15846. Just throwing out some more info to think about. This is way off the subject of thermostats, but may help someone save some money on a new ignitor or ignition module. Densoproducts.com has the ignitors for $67.00 plus shipping. Better than $275 from JD. Part # 131800-0131.
 

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Just wanted to thank the members who took part in this thread. Earlier this year I purchased a new to me 2001 JD 425 and it ran like crap. Installed the afore mentioned thermostat from Autozone and now it runs as good as my old "94" JD 425. Thanks again to you all!
 
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