B7200 running hot

[Paul Allwood]

The radiator top of tank will always read higher as it's steam and not coolant.
It could also be that you don't have the senso far enough down into the head.

Thanks, yeah, makes sense. Unfortunately there's not really enough material in the plug that I used to mount the sensor to move the sensor down much so I think I'll leave it at that for now and just monitor it. I had already taken a few mm off the top of the hex plug to move it down (but not by much), and drilled a clearance hole around the end of the sensor in the end of the plug to try to get it in contact with water and not the plug. Wonder if the sensor could be sitting in a small air pocket up inside the plug ? I'll loosen the plug to let any air out and see if it makes a difference.

I've also just checked and the coolant level is the same now after cooling for a few hours as before I started.

Happy it's running again and not getting hot.

 

[Hugo Habicht]

You get those sensors in different length. 1/8" NPT seems to be very common. What you have to do is measure the resistance at 25C to get the correct sensor.

You wrote that you bought everything in a set, but if the sensor resistance does not match the meter you would get incorrect readings too.

But I think your air pocket idea may be just the solution to the problem.

 

[Paul Allwood]

You get those sensors in different length. 1/8" NPT seems to be very common. What you have to do is measure the resistance at 25C to get the correct sensor.

You wrote that you bought everything in a set, but if the sensor resistance does not match the meter you would get incorrect readings too.

But I think your air pocket idea may be just the solution to the problem.

Thanks Hugo. I'll start by asking the eBay seller if they have a longer sensor.

 

[BAP]

Even if you don’t get an accurate reading, as long as it’s consistent, and you use that as a reference to monitor wether the tractor is starting to heat up too much.

 

[Paul Allwood]

Even if you don’t get an accurate reading, as long as it’s consistent, and you use that as a reference to monitor wether the tractor is starting to heat up too much.

Thanks, you're absolutely right. That's what I told myself when I fitted the sensor and gauge. If it wasn't for that annoying voice saying "it would be better if it was closer to right"....

 

[Hugo Habicht]

You could also add a parallel resistor to "tweak" the reading to be correct at nominal temperature (80ish °C).

Did you actually check the temperature near the sensor with your thermometer?

The sensor is fairly deep in the plug but I still think the reading should not be that far off.

But the important thing is that you fixed the radiator problem and that the cooling system works again.

 

[Paul Allwood]

You could also add a parallel resistor to "tweak" the reading to be correct at nominal temperature (80ish °C).

Did you actually check the temperature near the sensor with your thermometer?

The sensor is fairly deep in the plug but I still think the reading should not be that far off.

But the important thing is that you fixed the radiator problem and that the cooling system works again.

Thanks Hugo. I did try to measure near the sensor but couldn't find a large enough surface to get a sensible reading. Yeah, happy that the cooling system is fixed.

 

[Russell King]

Since you are living in the Metric world, you might be able to get a gauge sensor that screws directly into the port instead of using the plug as the adapter. You may also be able to get a sensor with a longer extension into the fluid.

There is also a whistle that can be installed on the radiator overflow hose. That is what was used on my L185 to alert you that it was overheating. The part number is 15021-72040 but is obsolete. You may be able to get one from the salvage market. I “know” I saw listings for new ones but couldn’t find it now. This salvage yard in the USA probably has some and could ship it to Australia???

 

[Paul Allwood]

Since you are living in the Metric world, you might be able to get a gauge sensor that screws directly into the port instead of using the plug as the adapter. You may also be able to get a sensor with a longer extension into the fluid.

There is also a whistle that can be installed on the radiator overflow hose. That is what was used on my L185 to alert you that it was overheating. The part number is 15021-72040 but is obsolete. You may be able to get one from the salvage market. I “know” I saw listings for new ones but couldn’t find it now. This salvage yard in the USA probably has some and could ship it to Australia???
View attachment 162936

Thanks Russell

 

[6869704x4]

Maybe a bushing would let you go deeper with the sensor.

 

[Paul Allwood]

You're probably right. I've just found and ordered one on eBay....

 

[North Idaho Wolfman]

I don't know if that bushing will work or not.
The original plug I do believe is 1/2 BSST.

 

[Paul Allwood]

I don't know if that bushing will work or not.
The original plug I do believe is 1/2 BSST.

Not on mine. I measured it as M16 x 1.5.

 

[Paul Allwood]

I fitted the temp sensor into a new bush today that got the sensor further out of the bush into the water. The Bush is a M16 x 1.5 - 1/8 NPT. After mowing for about an hour the temperature was steady at 64 deg C (147 deg F). Before changing the bush it sat at 60 deg C, so not much difference.

The attached pics show the sensor in line with the end of the first bush (made from the plug), and the sensor protruding from the new bush.

I think I'll be happy that it's running without overheating and leave it at that for now.

 

[Hugo Habicht]

Hello Paul,

You can measure the sensor resistance with a know good thermometer in a pot of water on a stove at around 80°C. And check the meter with a fixed resistor corresponding to 80°C.

All thermal things are often not very accurate due to time consuming and hence very expensive testing. Highlight I had so far was the Bosch oven of my sister that was 26°C hotter than displayed.

Kind regards,
Hugo

 

[Paul Allwood]

Hello Paul,

You can measure the sensor resistance with a know good thermometer in a pot of water on a stove at around 80°C. And check the meter with a fixed resistor corresponding to 80°C.

All thermal things are often not very accurate due to time consuming and hence very expensive testing. Highlight I had so far was the Bosch oven of my sister that was 26°C hotter than displayed.

Kind regards,
Hugo

Thanks Hugo