Even at that, you could have no coolant in your engine and it would not over heat in that length of time.
Need Help: ZD28 Temperature Fluctuating/Red Lining at Start Up
- Thread starter BrianF8
- Start date
Valid point. I'll troubleshoot the sensor tonight with a boiling pot of water and gradually cool it (or vice versa) while monitoring the temperature gauge.Even at that, you could have no coolant in your engine and it would not over heat in that length of time.
ehenry
Active member
Equipment
BX22, FEL, BH, 40" pto tiller, 42" Bushog Squealer, pto hole digger, B7300 w/60"
Brian, Kuboman is 100% correct.....if I were you I'd chase the wires to the temp sensor down. If no short is found.....replace the sensor....it cant be that expensive. You've spent more time, effort and headache boiling thermostats and such than what you'll spend on a temp sensor.
REPLACE THE TEMP SENSOR......and be done with it.
I'd be more concerned with the "brown/gray sludge gunk" you found in your radiator than a fluctuating temp gauge. Sludge in radiator could mean head gasket issues. You did mention "white smoke" at startup.
REPLACE THE TEMP SENSOR......and be done with it.
I'd be more concerned with the "brown/gray sludge gunk" you found in your radiator than a fluctuating temp gauge. Sludge in radiator could mean head gasket issues. You did mention "white smoke" at startup.
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I replaced the temperature sensor last night in addition to changing the engine oil, filter, and oil pressure sensor (it was corroded and housing was chipped). When changing the temperature sensor at the rear of the block it gushed coolant so I'm pretty confident there's no blockage issues. I'm still having temperature spikes. I placed a thermocouple on the exposed part of the temperature sensor and saw it peaked at 95C after about 3 minutes of running (white smoke stopped after 2 minutes) so the temperatures are real. It stabilized after about 6 minutes of running. I guess my earlier timing estimates were way off - this time I used a stopwatch. Feeling the radiator pipes the top is warm and bottom is cool so the heat exchange appears to be working properly. Is it possible this is just "normal" for this engine?
When you say thermocouple do you mean an infrared thermometer? 95c is like 200* F. It seems incredible that you can get those temps in that short of time. Is that from stone cold? If this is truly the case then you have something going on. Best guess is a blown head gasket or cracked head close to the sensor.
It was a thermocouple taped to the exposed portion of the thermal sensor, connected to a handheld fluke 51 (as an Engineer I have access to some nice loaner equipment). I used an IR thermometer to measure the temperature at the water pump. When the needle stabilized in the middle of the gauge both thermocouple at the sensor and IR at the water pump read 70-72C.
I was also worried about a head gasket. I went to the local kubota dealers and found out that they had the head gasket and thermal sensor replaced in 2005. I was hoping the sludge at the bottom of the radiator drain was still a remnant from that issue (I have no idea if the coolant had been flushed between then and now). I didn't notice any oil in the coolant or coolant in the oil, and if it were a head gasket wouldn't I be blowing white smoke continuously?
I was also worried about a head gasket. I went to the local kubota dealers and found out that they had the head gasket and thermal sensor replaced in 2005. I was hoping the sludge at the bottom of the radiator drain was still a remnant from that issue (I have no idea if the coolant had been flushed between then and now). I didn't notice any oil in the coolant or coolant in the oil, and if it were a head gasket wouldn't I be blowing white smoke continuously?
Are you using an infrared thermometer?And yes, the 95C is from stone cold, which yesterday wasn't so cold at 85F (or 29C).
ehenry
Active member
Equipment
BX22, FEL, BH, 40" pto tiller, 42" Bushog Squealer, pto hole digger, B7300 w/60"
If you run engine with radiator cap off do you see any foam/bubbles or is it trying to push coolant out?
I haven't tried that yet, but I can. Occasionally a couple drips will come out of the reserve tank tube (open to the ground), but no overflow at the radiator cap.
Thanks again for all the suggestions...if I can't figure this one out I'll eventually have it picked up by the dealer.
Thanks again for all the suggestions...if I can't figure this one out I'll eventually have it picked up by the dealer.
Will do. This weekend I'll take a thermal trace from start-up to stabilization so I'll have a nice graph to look at instead of trying to scribble down temperatures and times. I'm thinking I'll record: exposed part of the thermal sensor, water pump, top and bottom water pipes, and then maybe a few locations on the cylinder head between the sensor in the back and water pump up front. This will at least give me a baseline if I need to take it to the dealer.
I ran the temperature trace this weekend and also monitored the sensor voltage to the instrument gauge. It shows the red line spikes are start-up and stablized after about 8 minutes. My white smoke is pretty brief now, I'm guessing my oil and filter change may have helped.
Here's the link to the graph & pictures. Let me know if this helps with the troubleshooting. One person had suggestion drilling a small hole in the thermostat to allow fluid to circulate all the time, and in my situation at start-up. I can see how that could fix my problem, but if there's something bigger going on I'd rather not temporarily "mask" it unless this is normal or a known design issue.
https://www.dropbox.com/sh/8g04sa7hu8mgkad/AADeRYLPqANiAU6G1F5Pp1Kwa
Here's the link to the graph & pictures. Let me know if this helps with the troubleshooting. One person had suggestion drilling a small hole in the thermostat to allow fluid to circulate all the time, and in my situation at start-up. I can see how that could fix my problem, but if there's something bigger going on I'd rather not temporarily "mask" it unless this is normal or a known design issue.
https://www.dropbox.com/sh/8g04sa7hu8mgkad/AADeRYLPqANiAU6G1F5Pp1Kwa
Doubt a small hole will accomplish anything. Some thermostats come with a hole to aid in letting trapped air out. If your doesn't have one it sure won't hurt. It is possible you have air trapped but you might have a bad head gasket or crack and exhaust is being pushed into the cooling system.I ran the temperature trace this weekend and also monitored the sensor voltage to the instrument gauge. It shows the red line spikes are start-up and stablized after about 8 minutes. My white smoke is pretty brief now, I'm guessing my oil and filter change may have helped.
Here's the link to the graph & pictures. Let me know if this helps with the troubleshooting. One person had suggestion drilling a small hole in the thermostat to allow fluid to circulate all the time, and in my situation at start-up. I can see how that could fix my problem, but if there's something bigger going on I'd rather not temporarily "mask" it unless this is normal or a known design issue.
https://www.dropbox.com/sh/8g04sa7hu8mgkad/AADeRYLPqANiAU6G1F5Pp1Kwa
I think I figured out the root cause of the temperature spikes...
When starting up the tractor the other day I noticed the radiator overflow tank was bubbling, but it was cool to the touch so it wasn't boiling. When the thermostat opened and coolant circulated the bubbling stopped. Looks like I have a head gasket leak? I took the overflow hose and put it into a bucket of water and confirmed that exhaust gases were leaking into the coolant. I'm going to assuming the temperature spikes at the sensor are due to the exhaust gases and aren't actual engine temps.
I guess the question is - if my temperature is stable when using the mower, no white smoke after start-up, and the bubbles stop once the coolant is circulating, how important is it to get this fixed ASAP? I would probably leave this repair up to the shop ($$$?).
When starting up the tractor the other day I noticed the radiator overflow tank was bubbling, but it was cool to the touch so it wasn't boiling. When the thermostat opened and coolant circulated the bubbling stopped. Looks like I have a head gasket leak? I took the overflow hose and put it into a bucket of water and confirmed that exhaust gases were leaking into the coolant. I'm going to assuming the temperature spikes at the sensor are due to the exhaust gases and aren't actual engine temps.
I guess the question is - if my temperature is stable when using the mower, no white smoke after start-up, and the bubbles stop once the coolant is circulating, how important is it to get this fixed ASAP? I would probably leave this repair up to the shop ($$$?).
I ran a 150hp tractor for years with exhaust pressuring the coolant system to the point where there was a blast of air coming out the rad overflow. Finally fixed it but never did any harm. With yours though you are getting temp spikes at startup which means you have a leak likely right at the sensor which creates a pocket of no coolant for a period of time. You probably won't hurt anything but then again......Might want to fix it sooner than later.I think I figured out the root cause of the temperature spikes...
When starting up the tractor the other day I noticed the radiator overflow tank was bubbling, but it was cool to the touch so it wasn't boiling. When the thermostat opened and coolant circulated the bubbling stopped. Looks like I have a head gasket leak? I took the overflow hose and put it into a bucket of water and confirmed that exhaust gases were leaking into the coolant. I'm going to assuming the temperature spikes at the sensor are due to the exhaust gases and aren't actual engine temps.
I guess the question is - if my temperature is stable when using the mower, no white smoke after start-up, and the bubbles stop once the coolant is circulating, how important is it to get this fixed ASAP? I would probably leave this repair up to the shop ($$$?).
Sorry for the late update, but the root cause was a cracked cylinder head. It was not a cheap service call but I found a good mechanic and shopped around for new OEM parts and she's back in business...no more burning coolant, white smoke, or irregular temps are start-up. The prior owner had concealed the issue (for a short time) with some stop leak in the radiator.