Jinma 204 (TY290) temp issues

[Catch95]

Continuing saga which you may have seen in my previous posts.

I was losing coolant but not from anywhere obvious, overheating quickly, coolant coming out of the overflow, lots of pressure if the radiator cap removed, could hear bubbling in exhaust etc. Suspected faulty head gasket so changed that. The gasket was shot. Put it back together and after some mucking around with a copper washer on an injector which stopped the injector seating properly, I have it back and running happily - except the temp gauge is still moving into the red after only 10 minutes or so. I have cleaned out the radiator, new 7psi cap, put in a new thermostat (which I have taken out at the moment as it is warm here). The radiator needs replacing as it copped a beating with excess pressure due to the head gasket issue. I have a new one on order but for the moment it is not leaking and is clean (can see through the fins etc and back flushed etc.

When the gauge has moved into the red (starts at cold and moves up over 10 mins or so) the engine is not hot - I can put my hand on the the radiator or the thermostat casing. Warm/hot but not burning. So could it be a faulty sensor?

I read some posts and tried removing the wire from the sensor and grounding it. The gauge moved hard right into the red. Before I fork out for a new sensor and the cost of getting it to Australia, I'm wondering about the electrics. I have the cluster of gauges not the old style individual ones. The temp gauge shares a fuse with the fuel gauge above it. The fuel gauge is stuck hard right on full. All this is recent.

I understand these temp sensors work on resistance but is there any way of testing if the sensor is faulty?

Any other thoughts on the fuel gauge??

Many thanks

Mark

 

[sweettractors]

Mark, try measuring the temp with a conventional thermometer designed for that purpose. Your gauge or sensor could be faulty? Ken Sweet

 

[Catch95]

Hi,

What should be the normal operating temperature for a 2cyl Diesel engine?

Thanks

Mark

 

[quicksandfarmer]

Around 185F/85C.

Here's the way I see it: either your engine is running hot, or the gauge is wrong. If the engine is hot and the radiator isn't, water isn't circulating. You've already said the thermostat is out so the pump isn't working or the water is somehow obstructed, or there isn't enough water in the system.

If the gauge isn't working, it's either the gauge or the sender. This thread has some info about checking the gauge:

http://www.tractorbynet.com/forums/...-there-any-aftermarket-temperature-plugs.html

 

[Catch95]

Thanks for your thoughts. Back up at the farm and used a thermometer to test the tractor operating temp. After doing some work on a warm day, the guage had gone into the red. I put the thermometer in the radiator water and got a reading of 70 C. I did some more work with it and brought it back with the gauge fully over on the red. Highest reading was 79 degrees Celsius.

So as suspected it is not running hot but it is a faulty gauge or sensor.

I tested the gauge by grounding the lead that goes from the sensor to the gauge. It sent the needle in use gauge hard to the right (red). Which from what I read means the gauge should be ok?? Still dubious about the gauge. It shares a fuse with the fuel level gauge. Fuse is fine but fuel gauge is permanently hard over to full. Could be a stuck level sensor in the tank but haven't gone down that road yet. Just seems strange to have problems with two gauges that shard a fuse....

How do I test the sensor? It only has one terminal. At $45 for the sensor + freight to Australia I'd rather test it than just replace it.

Any thoughts much appreciated

Thanks, Mark

 

[RonMar]

DO you have an ohm meter? The resistance from the single terminal on the sensor to ground should vary with the coolant temperature. Unfortunately I have not seen a temp-resistance chart for the Jinma temp sensors. It sounds like it's resistance is varying with engine temperature as the gauge souds like it is starting at the bottom and shifting into the red, but without the temp-resistance info, you cannot tell if the sensor is delivering the proper resistance, or the gauge is failing to use the proper resistance.

One other thing you can check is the power at the gauge itself. You say both gauges that share the same fuse(fuel level and temperature) read incorrectly? If for some reason they were both receiving insufficient voltage/current, this could be causing them to read incorrectly...

 

[Catch95]

Ron,

Thanks for that. I'll run a meter over it in the morning and see if the resistance changes at all.

Mark

 

[quicksandfarmer]

Thanks for your thoughts. Back up at the farm and used a thermometer to test the tractor operating temp. After doing some work on a warm day, the guage had gone into the red. I put the thermometer in the radiator water and got a reading of 70 C. I did some more work with it and brought it back with the gauge fully over on the red. Highest reading was 79 degrees Celsius.

If the water pump isn't working or there is a blockage then the radiator water won't be at engine temperature.

 

[Catch95]

The sensor screws in close to the thermostat housing so the water in the radiator should be a similar temp I would have thought? I took of a cap of the rocker cover and put the temp probe in there (with the engine off!) and the reading was lower. There is plenty of water going through the engine as if I open the drain cock on the engine it pours out. Refill it, and plenty comes out if I open the engine drain ( this is not the radiator drain but the one at the back of the engine).

Any other way of testing the water pump? It is not leaking around any of the seals or the front.

Will try the ohm test on the sensor and see how I go.

Thanks

 

[SPIKER]

With the rad cap open and engine up to temp you should see flow of coolant in the radiator as pump moves it thru.

Take a COLD resistance reading of the sensor, then with engine up to temp measure the resistance of the sensor again. Record those two readings and compare them to on-line specs if you can find any. if not then find a 10K potentiometer, attach it between the sensor wire and eng ground. Start out with the 10K resistance between the two, and slowly back it down. When the gauge just starts to read that should be the COLD temp adjustment of the two. As the ohms come down the temp gauge goes UP and when you get to 100C that should be the resistance of the sensor at boiling water temp. measure this reading using the ohm meter and record it. pull out the sensor and put it into boiling water same as it would be when mounted, then measure the resistance from case to pin/terminal. those two readings should be about the same reading. You can do the same at the bottom (0c) scale by using crushed ice and water but I dont think the gauge can read that low.

I would check ALL of the engine and gauge grounds as this is one of the major problems with gauge accuracy on these things.

Mark

 

[Catch95]

I took some temp and resistance readings - hope I did that correctly. I also drained some water from the block to test the temp in that.

After working it for an hour and gauge hard into the red. Gauge: 120. Radiator: 75. Block water: 68. Ohms 30. Engine didn't feel or smell hot. Radiator cap ok to touch.

After running for 20 mins - Gauge: 90. Radiator: 56. Block water 50. Ohms 35

Does that make any sense? tempted to put in a mechanical temp gauge as the electrics on these are always playing up.

I'm going to pull the gauge cluster and check those next. Got distracted with a sick calf that got bitten by some ticks. Not sure if it will make it yet. Lost one last year as well. Trying vitamin c injections.

Thanks

Mark

 

[quicksandfarmer]

This site has ohmmeter readings:
http://johnstractor.homestead.com/files/MeterReadings.htm

They report 7 ohms for the temp sensor cold.

 

[Catch95]

Thanks for that - very helpful. On a cold engine with ambient air temp of 30 degrees C (86 F) the OHM reading was 50 (or 5). So the chart suggested 7 ohms at 70 F. My sensor then read 3.5 at 56 degrees C in the radiator, then 3.0 at 75 degrees C.

So the higher the temp, the lower the OHM reading. Is that what I should be getting?

In which case that suggests the sensor is ok and is an issue with the gauge. I've done the test on grounding the sender wire (which pushed the gauge hard over) so I guess that suggests a bigger issue with the gauge cluster. Maybe a bad earth.

Am I on the right track?

Thanks for your help

Mark

 

[Catch95]

Final update on this.

Gave up on the Jinma gauge and put in a mechanical one. For those of you in Australia, a Speco one with an adaptor to the right size to screw in the sensor did the job. Reading is consistently around 80-90 degrees C which is where I understand it should be be. Pretty warm here at present so happy with that.

So running nicely with its new head gasket and new radiator!

Thanks for all your help.

 

[doxford jim]

I think the Jinma's are a tough little tractor and pretty good value for the money - at least here in Canada. I only paid about 25% of what a major brand tractor would cost in 2007. Tractor was $9800 US and FEL $3500 and both were new. I don't think you can beat that. What problems I have had have been relatively minor or slef inflicted. For the money I would buy another Jinma or a Dong Feng.