Strange Temp reading behavior

[analog_me]

Hi,

Lately my water temp reading on my 1999 k-series is showing high temperatures of about 90 to 100C.
Usually it sits firmly at 80C.
I noted once i stop the temperature drops to normal (80C) withing 3-4 seconds. You can actually see the needle moving.
Once you start driving it goes back to 90 or 100C.
I have a dual switch changing the water to the oil temperature and i think (!) the oil temperature does not do this (i think so)
I thought it was heat induced since the sensor and wire connected on the coolant pipe are above the exhaust but i insulated them well with nimbus then with exhaust wrap but showed no difference...
Can you give me some hints on what this might be???
Thank you

[Paul Philpot]

Check for air locks in the system. I had a similar issue.

[analog_me]

i will check again with the nose higher up thank you