A question about thermostats, radiators and engine temperature.

3435 Views 7 Replies 6 Participants Last post by hugo.atx, 7 mo ago

hugo.atx

Discussion Starter · 7 mo ago

Hi guys.

I'm doing some checks on the actual temperature of my engine. As some of you know, I have a 2021 Vstrom 650 XT.

And my question is... Can the temperature data shown on the panel be incorrect?

What is displayed is the temperature of the liquid near/inside the radiator or the temperature of the liquid that is in the engine?

From my lack of knowledge, I understand that a broken thermostat or a blockage of the water pump, will keep the flow immobile, and the radiator would always have a soft temperature (because the air cools it), keeping the heat in the engine, correct?

In this case, we would be driving with a very hot engine and the panel would show incorrect data. Surely Suzuki has thought about this and there are safety systems... but I would like to know your opinion. Thanks in advance.

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GoodDl

· #2 · 7 mo ago

hugo.atx said:
Hi guys.

I'm doing some checks on the actual temperature of my engine. As some of you know, I have a 2021 Vstrom 650 XT.

And my question is... Can the temperature data shown on the panel be incorrect?

What is displayed is the temperature of the liquid near/inside the radiator or the temperature of the liquid that is in the engine?

From my lack of knowledge, I understand that a broken thermostat or a blockage of the water pump, will keep the flow immobile, and the radiator would always have a soft temperature (because the air cools it), keeping the heat in the engine, correct?

In this case, we would be driving with a very hot engine and the panel would show incorrect data. Surely Suzuki has thought about this and there are safety systems... but I would like to know your opinion. Thanks in advance.

Usually t-stats fail in the open position, due to spring weakening, resulting in too much coolant flow. Aka an engine that doesn't warm up properly. Under normal circumstances I cannot think of a reason a cooling system would be blocked so much to be a problem.

Different engines have the coolant temperature sender in different places, sometimes multiple sensors and the outputs are inserted into an algorithm via ECU. They can calibrate them so that even if the sensor is on the hot-side radiator hose, the readout can be adjusted for what the cylinder head/block would be based on a table.

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PeteW

· #3 · 7 mo ago

The thermostat on my 2012 DL 650 failed open about 5 years ago. Since I live in Queensland Australia (Well above 0C even on cold days) it's a don't care. The engine still warms up, it just takes a lot longer - given it's 20 minutes for me to get out of town it doesn't matter with my use. 30 seconds and on a freeway, yeah it'd need fixing.

Water pump failure will kill the bike as it's on the same shaft as the oil pump. That one is really unlikely though dumping undiluted coolant concentrate in the system is a very reliable way of causing that. (Crystalizes and the pump wears away, as does the pump shaft and the seals).

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hugo.atx

Discussion Starter · #4 · 7 mo ago

Sorry for the delay in replying.

Thank you very much for your answers.

In my case, I have experience with the thermostat closed.

On a trip to France on my old and beloved '96 CB500, about 5 years ago, I suddenly saw how the engine temperature was approaching the red line.

I stopped as soon as possible, and saw that there was a blue dust on the rear tire.

It was the coolant that had evaporated, and it had to come out somewhere... the coolant drain pipe.

I had to refill it with the first thing I could find, distilled water.

Oddly enough, it has never happened to me since... it was dramatic. I have very bad luck when I travel... Something always happens!

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jathkajoe

· #5 · 7 mo ago

Travel more. The bad things become less per mile/kilometer traveled.

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Quimby

· #6 · 7 mo ago

hugo.atx said:
... Can the temperature data shown on the panel be incorrect?

Yes. If the engine coolant temperature sensor is defective, it will cause the dash indicator to show the incorrect reading (ie wrong number of bars for the current engine temp).

hugo.atx said:
What is displayed is the temperature of the liquid near/inside the radiator or the temperature of the liquid that is in the engine?

I believe the temperature sensor is located in the same body as the thermostat, but on the cylinder side of the thermostat. (Eg where I have circled in red, below).

This means the dash always shows the coolant temperature on the engine side, regardless of whether the thermostat is open or closed. (This is confirmed because we see the engine heating up, adding bars on the display, before the thermostat opens).

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Brockie

· #7 · 7 mo ago

Every ICE that I have ever looked at always has the temperature sender unit in the engine water circuit. To have it in the radiator would be meaningless.

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hugo.atx

Discussion Starter · #8 · 7 mo ago

Quimby said:
Yes. If the engine coolant temperature sensor is defective, it will cause the dash indicator to show the incorrect reading (ie wrong number of bars for the current engine temp).

I believe the temperature sensor is located in the same body as the thermostat, but on the cylinder side of the thermostat. (Eg where I have circled in red, below).
View attachment 309409

This means the dash always shows the coolant temperature on the engine side, regardless of whether the thermostat is open or closed. (This is confirmed because we see the engine heating up, adding bars on the display, before the thermostat opens).

Thank you very much Quimby.

A perfect explanation, and I think with this I have some peace of mind. If the temperature we get comes from the engine, and it stays on the 3 lines, then it means that everything is correct. In my case, I think the sensor is not defective, because when cold it goes from 0 to 3 lines in a normal way.

If it were defective I think it would fail both in cold and hot.

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