4.6is strange coolant temp issue

[x5Alpine]

So I unlocked the cluster to display actual coolant temp on my 4.6. it has always been around 105c and gone down to 95c when gong up hill for a while as designed. However, this evening it hovered constantly around 90c but the second I switch the engine off it immediately reads 105c. does one coolant temp sensor work only when the engine is on (radiator hose sensor or the sensor on the thermostat). I would say that its the thermostat but that doesn't explain how the temp immediately changes from 90c to 105c after the engine is shut off.

[Purplecty]

Originally Posted by x5Alpine

So I unlocked the cluster to display actual coolant temp on my 4.6. it has always been around 105c and gone down to 95c when gong up hill for a while as designed. However, this evening it hovered constantly around 90c but the second I switch the engine off it immediately reads 105c. does one coolant temp sensor work only when the engine is on (radiator hose sensor or the sensor on the thermostat). I would say that its the thermostat but that doesn't explain how the temp immediately changes from 90c to 105c after the engine is shut off.

I believe the dual coolant temp sensor reads on ignition 1 and 2 and if you are seeing a difference the dual temp sensor should be replaced.

https://www.fcpeuro.com/products/bmw...ch-13621703993

[andrewwynn]

Change from heat soak and loss off cooling.

Much of the engine is much hotter than the coolant temp (or it wouldn't work). Turn off the engine the water pump stops and the hotter parts will transfer heat to the still coolant where the sensor is located.

[x5Alpine]

yes I understand that the temp will go up after the engine is shut off however the temp jumps 15 degrees the second the engine is shut off and doesn't raise gradually over a few minutes before cooling down.

[EODguy]

+1 What Purplecty said

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