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MikeC
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2000-10-16          20632

I think my JD855 might be runnning too cool. This would help explain some of the excessive exhaust smell/smoke. I took out the thermostat and heated it in a pot of water along with a thermometer. It seems to be opening at about 160 F. I own the technical manual for this tractor, but I can't find any reference to the correct water tempeture. Does anyone know if 160 F. is too low? I would have thought a deisel would want to run at 180 or higher. Thanks in advance for your help.

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Bird Senter
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2000-10-16          20633

Mike, I can't say for sure on John Deere, but would think it would be about the same as my B2710 and the manual says "opening temperature" should be 176.9 to 182.3 and completely open at 203F. In other words, I think you're right; may need a new thermostat. ....

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MikeC
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2000-10-23          20801

OK, here's the rest of the saga... In addition to only reaching 160F, the temperature would fluctuate between 160F and 100F. It would slowly rise to 160, then drop fairly quickly down to 100, then start the cycle over again. I assumed the temperature was dropping when the thermostat opened, but why so low? I installed a new thermostat, and then the temperature cycled between 180F and 100F. Next, I covered 2 thirds of the radiator screen with duct tape. Then it cycled between 120 and 180. Next, I drained the coolant and refilled with antifreeze concentrate, no dilution. Now it cycles between 135 and 180. I'm still confused. Next I think I'll try removing the radiator completely and wrapping the engine in an electic blanket. Any thoughts? ....

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Bird Senter
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2000-10-23          20816

Mike, right now I don't know what would cause the temperature fluctuations you're talking about, but I do know you don't want to run undiluted antifreeze. In fact, it should be no stronger than 50/50 mix. Where and how are you taking the temperature that gets those fluctuations? ....

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TomG
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2000-10-24          20827

I believe that cooling systems have to have the rad cap in place for normal operation. If temperature readings are taken with the cap off and with the engine at idle, the readings may not reflect actual operating conditions.

However, what you describe may be normal at idle speed. The temperature sensor is taken from the engine coolant. Before the thermostat opens, there is little circulation between fluids in the engine and in the rad. Temperature in the rad is cool relative to the engine. When the thermostat opens, cool fluid from the rad flows into the engine, and the temperature decreases. The thermostat closes, or partially so. While the thermostat is closed, temperature in the rad cools, and temperature builds again in the engine. If the engine isn't producing much heat at idle, the temperature swings could be fairly wide.
....

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MikeC
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2000-10-24          20836

Bird, I forgot to mention that I installed an electric automotive type water temp guage. I put the sender in a existing threaded hole in what looks like the output side of the water pump housing. The sender for the over-temp idiot light is right next to the thermostat - on the engine side of the thermostat. Would the location of my sender affect the readings? Tom, I checked the temp both at idle, and while mowing. It did seem like the temp swing was a little more at idle. Also, what's the problem using undiluted antifreeze as long as your engine is not overheating? Thanks. ....

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MikeC
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2000-10-24          20838

Bird, I forgot to mention that I installed an electric automotive type water temp guage. I put the sender in a existing threaded hole in what looks like the output side of the water pump housing. The sender for the over-temp idiot light is right next to the thermostat - on the engine side of the thermostat. Would the location of my sender affect the readings? Tom, I checked the temp both at idle, and while mowing. It did seem like the temp swing was a little more at idle. Also, what's the problem using undiluted antifreeze as long as your engine is not overheating? Thanks. ....

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Bird Senter
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2000-10-24          20842

Oops, somebody help me out here. I know you don't want to mix ethylene glycol anti-freeze stronger than 50%, but it's been a long day, I'm getting old and forgetful and can't remember why now. Of course, my tractor manual (as with car manuals I'm familiar with) says "When the anti-freeze is mixed with water, the anti-freeze mixing ratio must be less than 50%." and "The procedure for mixing of water and anti-freeze differs according to the make of the anti-freeze and the ambient temperature, basically it should be referred to SAE J1034 standard, more specifically also to SAE J814c." ....

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TomG
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2000-10-25          20854

I don't know the 'mixing question' answer either. I think I used to run undiluted anti-freeze in my cars years ago and nothing bad happened. However, all the sudden, there seem to be these warnings that the stuff has to be mixed. Box stores even sell it already mixed. Don't know, but maybe somebody will say. ....

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Rob Munach
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2000-10-25          20856

As I recall from college chemistry class, the antifreeze will "freeze" at a lower temperature when mixed with water. I think there is some optimal ratio, but I can't remember it. ....

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mbjacobs
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2000-10-25          20861

A 50:50 mixture of ethylene glycol and water freezes at about -40 F. Pure ethylene glycol freezes at about 0 F. The only other reason I know of for not using straight antifreeze is that it's a waste of money. ....

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MikeC
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2000-10-25          20880

Thanks. It didn't occur to me that pure ethylene glycol would have a higher freezing temp than mixed. I tried pure because I know that water is better at carrying heat away from the engine (higher thermal capacity, and better heat transfer?) than ethylene glycol. I was trying to make the engine run hotter, but it only made a marginal difference. ....

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Roger L.
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2000-10-26          20926

Mike, by using a brass "T" or "Y" fitting you can put the idiot light and the temperature sender on the same side of the thermostat. You want to be looking at the engine side temperature. I would not put too much stock in the temperature readings until they are taken at the engine side. I use the T connector system on my own tractor. My tractors seem to run hotter than yours. One is a thermosiphon type and is designed to run quite a bit hotter than the pump and thermostat engine. When working hard, the thermosiphon runs over 200 degrees F and the more traditional waterpump cooled engine runs around the 190 degree level.
Thermostats should open slowly as the temperature rises. I wonder if both of your thermostats are opening too wide and too quickly.
Good on you for having a shop manual at all, but you have probably noticed that JD's shop manual for the 855 is poorly done....and I am being generous. The engine (3T75 series)is a standard engine made by Yanmar and used in a lot of their machinery. Yanmar itself publishes excellent parts and service manuals and they are still in print. If ou like this sort of thing, they are worth the price. The Yanmar YM220 through YM226 series of tractors used the 3T75 series engine, and these manuals might give you some insight on the design. JD did make some changes to that engine for the JD855. In fact, I think I remember that it has a different configuration to the water pump, with the pump and thermostat being in a common casting. Does this sound right to you? ....

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MikeC
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2000-10-27          20947

Roger, I couldn't agree with you more. The 855 manual could be about 1/4 of the size given the amount of useful information it has in it. Also, the photos are poor quality. And I paid $70 for it! I think your right - the thermostat is in the water pump housing. I'll try moving the sender next to the idiot light. I would love to find a good engine manual. Is there a good place to find the Yanmar manuals on the Web (or elsewhere)? Thanks. ....

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Roger L.
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2000-10-27          20948

Mike, sometimes I order from Len Shaeffer....he posts on this list and is a Yanmar dealer. Others I pick up from bidding on Ebay or from tractor literature re-sellers. While cruising through my little library this morning I realize that I do have a Yanmar 226 parts book and the shop manual both....as well as the same for the 855! I had forgotten all about them! So if there is some particular question that you have I can probably find the answer. I am surprised to find that the workshop manual lists that the thermostat on the YM226 should begin to open at 160 degrees F (71 C). (they have a picture of a thermostat suspended by a stick and a cord into a pail of hot water to test it :-)) The system is designed to work at 12 to 14 psi, and the temp. warning light comes on at 230 degrees F. So after all of our thinking, it turns out to be an engine designed to run cooler than we thought. ....

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MikeC
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2000-10-27          20949

Roger, I couldn't agree with you more. The 855 manual could be about 1/4 of the size given the amount of useful information it has in it. Also, the photos are poor quality. And I paid $70 for it! I think your right - the thermostat is in the water pump housing. I'll try moving the sender next to the idiot light. I would love to find a good engine manual. Is there a good place to find the Yanmar manuals on the Web (or elsewhere)? Thanks. ....

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MikeC
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2000-10-27          20950

Roger, I couldn't agree with you more. The 855 manual could be about 1/4 of the size given the amount of useful information it has in it. Also, the photos are poor quality. And I paid $70 for it! I think your right - the thermostat is in the water pump housing. I'll try moving the sender next to the idiot light. I would love to find a good engine manual. Is there a good place to find the Yanmar manuals on the Web (or elsewhere)? Thanks. ....

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MikeC
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2000-10-27          20954

Roger, thanks for the offer. It's good to know about your tractor library. I'll probably have another question for you before too long... But now I really want to get an engine manual after finding out that it's supposed to run at 160F! ....

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Roger L.
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2000-10-27          20958

Mike, I just looked in "3TN and 4TN Series Yanmar Diesel Engines". This is a Technical Manual published by John Deere for their compact tractors up until recently. It is much better than the 855 shop manual, though not in the same league as Yanmar's own publication. The test for the thermostat is described as just beginning to open at 160 F and fully open at 184 F. So it is consistent with Yanmar's own source.
This still leaves us with the mystery of why cools so well. But maybe it doesn't cool especially well, and that is just where it should run. How does it run other than the heavy diesel fume? BTW, is the smoke white or black? ....

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MikeC
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2000-10-29          21012

It runs very well. No other problems, good power, starts easy, etc. The smoke is black. In addition to the nuisance of the smoke & fume, I am concerned about carbon build up. ....

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Roger L.
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2000-10-29          21015

Oh. If that is all that is bothering you then you might want to try what I have done to fix both problems. First of all: The Fumes. If your compact is like mine, it has a stack that is at head (and ear) level and is designed to blow the fumes just far enough out to the side so that any stray gust of wind blows them back right in your face. If there is no wind, you may find that your own forward motion is sufficient to saturate your airways. Even if you miss the black cloud of soot, the noise remains.
What I did is take that 16" tall double walled side exit stack that clamps to the top of my stock muffler and replaced it with a 30" tall piece of straight plated thinwall steel tubing. This makes an exhaust pipe which slides right over the spigot on the muffler and clamps with a U bolt.. Now the fumes and noise are blown straight up and away. Makes a much bigger difference than you think. Why 30"? Well, that is the height that will clear my shed door and still has roughly similar back pressure to the original pipe with its bend at the exit.
As for the carbon build up, there are additives which you can put in the fuel now and again which remove carbon from the combustion chamber. B&G makes one specifically for diesels which I have used for injector cleaning and de-cokeing. ....

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MikeC
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2000-10-31          21065

Thanks for the advice. I read your post today, but coincidentally, I had ordered a quart of Dee-Zol Plus yesterday. I wasn't sure which brand additive to use since they all claim roughly the same benefits. ....

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MikeC
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2000-11-12          21442

Roger, you were right. Moving the temp. sender to the engine side of the thermostat made a surprising difference. I get only a 10 deg. temp. swing now. That seems reasonable. For the record, I still have about 3/4 of my radiator blocked off with duct tape. I'm operating in 45-65F temperatures. Apparently, this engine doesn't produce a lot of heat! It turns out that JD actually lists two different replacement thermostats for this engine. One rated at 160F (as specified in your Yanmar book), and one at 180F. I ended up with the 180F, and the engine runs between 175 and 185, as expected. I wonder why they specify diffent temperatures with no explanation. I'm mostly interested in what's best for the long-term health of the motor. 180F is typical, but did Yanmar design the motor for 160? ....

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Roger L.
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2000-11-12          21446

No, I didn't know about the two thermostats. My JD shop manual and the JD parts book only show one thermostat for the 855. It is part #M801088 and is listed as beginning to open at 160 F and fully open at 184 F. It sure wouldn't surprise me if one of these was off by a few degrees....like 20 degrees....The only way I know to test them is with a lab thermometer as it sits in a pan full of water on the stove. Diesels don't run all that hot in any case, and they run unusually cool at low speeds and loads. For the long term health of the motor, I don't know whether 160 or 180 F. is best, though I lean toward 180. One of the reasons for specifying a running temperature at all is so that the designer can balance the various engine hot spots versus the coefficient of expansion of the metals in that hot location. The worst of these temperature gradients ocurs right inside the combustion chamber itsef, but the difference of 20 degrees F just doesn't make much difference to the metal to metal fit. Since we are just guessing here, I'm going to go with the most thermodynamically efficient guess and say that I'd prefer to see it running at 180 rather than 160....and I'm betting that Yanmar designed it to do so. ....

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TomG
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2000-11-13          21448

This note may have some relevant information. I replaced my thermostat yesterday, because the temperature gauge never got much off the cold peg (@ 1500 idle speed) until the tractor was worked some. It works fine now. The temperature comes up into the normal operating range in about 5 minutes at idle. I believe that most engines should do that. When I had the thermostat housing disassembled, I noticed that the old gasket was installed on the wrong (at least to my way of thinking) side of the thermostat. I believe the proper assembly for my tractor is: The thermostat is placed in a recess in the housing, the gasket goes over the thermostat and between the housing and cylinder head. Placing the gasket on the housing before the thermostat forces gasket material into the recess designed to receive the thermostat. However, I don't know if the 'backwards' gasket allowed additional coolant to flow around the thermostat, which produced the long warm up times. But anyway, it works properly now. I don't suppose it makes a lot of difference if I had a stuck old thermostat or a new thermostat stuck with a bad installation.

I agree with Roger. I’d use the hottest factory recommended thermostat. Within limits, hotter gives a bit more power and shouldn’t affect engine life much. Few of us are going to wear out a tractor engine anyway. The only exception I can see is for somebody who sometimes works a tractor really hard—beyond the capacity of the cooling system. In that case, starting off cooler will allow a tractor to sustain slightly longer peak loads. There is an assumption here that tractor cooling systems are slightly under-designed. Excessive cooling of rad fluid may be as much a problem as excessive heating. Back in the 50’s and earlier, some auto cooling systems weren’t great, and people talked about summer thermostats and winter thermostats.
....

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Roger L.
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2000-11-13          21452

Great post, Tom! I believe I've seen the same problem with gaskets and thermostats before. I KNOW I've sat there with both in my hand and pondered which way around that I should install them - wishing that I had written myself a note when I took it apart.....
And you are right on with the Summer and Winter thermostats. In fact, lots of things for machinery used to be either/or - and "depending on the season". The current crop of "all-season" products is relatively recent. ....

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Art White
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2000-11-13          21456

Roger you will love this. A number of years back I picked up a Jeep cherokee that needed some work. Did the work sent out my wife to work in it(she had to have one for work to get her over the hills in the winter). This veichle had the little 4cyl. in it and seemed to run fine but she complained the temp gauge went up when climbing hills (I never thought she looked at that stuff). So I started playing, first the radiator was pulled and cleaned, seemed to have good circulation but it still would warm up as before. The next step was the water pump because every thing else was right. Last step was the thermostat and still a failure! When I was talking to a friend in the auto repair field he brought up a friend that I had forgotten that worked on them at the local dealer. When I called and talked with him he told me those gauges always do that because the gauge sending unit is on the back of the engine and the thermostat is on the front of coarse and that was why it was doing it. I wasted a bunch of time and some money, I sure do wish I had done more reaserch before I got started! ....

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TomG
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2000-11-14          21485

Thanks. I did get curious after I installed the thermostat and checked the repair manual to see if it indicated where the gasket should be installed. It doesn't, and there is no exploded diagram. However, the text does list the parts for removal and installation of the thermometer in the order I installed them and has a picture of the parts laying on a table in the same order. It makes sense, and probably should be a requirement of good tech writing, that a writer would describe parts in the order of assembly. Even though, I'm not sure it's safe to make an assumption of that level of writing quality in repair manuals, using this type of information is probably better than a wild guess. Besides, in this case, if I'm wrong, I can blame it on somebody other than myself. ....

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