Coolant temp goes wacko

I have a 2550 2WD with the 239ci 4 cyl engine. The coolant temp gauge pegs when hot. I use a laser temp gun and it reads anywhere from 190 to around 210 on the inlet and outlet from the radiator depending on how hard I run it. Gauge starts jerking back and forth then pegs. Been doing this for a few years and I have not yet found the cause (I suspect the tach assy). Is there a good second port where I can install an aftermarket temp gauge or should I just pull the existing sender and put the aftermarket one there?

So far I have replaced the sender, and traced wires thru the bulkhead connector with no joy. I think the issue is in the tach/gauge unit. There is condensation on the face so I am betting it needs to be pulled and rebuilt. Not a good time now.

John

Another question, what is the proper operating temp for this tractor?

I have a 2550 4wd and I seem to have the opposite issue. Cold blooded doesn't begin to cover it. Anytime I start it I plug in the block heater. Mine does not get the temp gauge halfway even with working it hard. I disked yesterday with it for 3 hours and it barely moved the needle past 1/4 on the temp gauge. Sorry I wasn't more help.

180 would be typical temp and then the EPA happened upon the scene and with the all important estimated MPG sticker in the window, the trend was started for higher and higher operating temps up to 195 which is actually only geared to getting the oil hotter to be thinner for less friction and the best possible MPG sticker number. Nothing else has driven the higher temp issue that is important but pundits rarely fail to point out that emissions are the driving force. I doubt that very much because they would never talk BS out the side of their face while ignoring the replacement of real gear lube for anything thinner than water as long as it's synthetic and priced out of this world. 5w-20 will become standard due to variable cam timing mechanisms and precise computer control of same via oil pressure timing control circuits which are emissions issues so full circle we will go -- no substitute allowed for that flavor of oil either, it may be dealer only item too. Because if you don't receipts for it, then your warranty is null and void.

190 is not hot, 210 might be warm. 240 is the typical 'having actual troubles' point and this should be in the red region if your gauge goes by colors. Fix the issue at this temp, do not operate as if it's still OK. It does sound like the gauge in both these tractors isn't telling the truth, which is an all too common failing of OEM temp gauges. Dumping money on them probably only gets you a lighter wallet as the truth you are after probably can't be purchased in any event. Can't beat a cheap IR temp gun for this kind of real information input.

I have never seen the temp above 220 degrees using the IR temp gun.

I have this heater on the side of the engine. Can I substitute a running tee for the elbow and insert a temp probe there and expect to see consistent engine coolant temps? Or perhaps remove the grain cock from the lower hose and put it there. Would not be that much of a pain to remove the sender when I drain the coolant every few years. Or I could power flush the system and not have to drain it.



John

Moving the temp sender to this location might not read the hottest water as there won't be any real flow from the bottom of the water jacket to the mid jacket location and it's likely to be the coldest water in the engine too. The tank heater works fine here due to it's own temp difference that it has created when plugged in, but otherwise there is no reason for the water to really flow thru the heater even with the water pump turning. Hottest water will be found right under the thermostat which is where the original temp sender probably is right now. The water there is being pushed thru there by the water pump with very good flow too.

Please explain your thoughts in moving the sender here as to a solution for inaccurate readings stock system seems to be plagued with. An additional bulb type mechanical temp gauge will be the most reliably accurate temp gauge you could put in there, and even these benefit from a calibration run on top of the kitchen stove with the bulb in a pot of boiling water to verify where boiling temp is actually at on the meter scale. You could put factory sender here and use the original location for mechanical gauge, since factory one is going to lie anyway. Either spot at the tank heater works with about the same, not so optimum results, make it easy on yourself would be my advice as which to which location/method to use there all those proposals have their merits if this is to be the location for the inaccurate factory sender and a second gauge will be used in the best spot for it.

Never above 220 tells me that your system is in fine working condition after all. Even these water pumped, thermostated systems rely somewhat on higher temp difference to do a lot of the cooling with. A radiator flowing full blast with 180 temp water (80 diff) won't shed near as much heat as when the water is at 220 (120 diff -- 150% hotter) in other words.