chevymetal

Hi There!

First I have to say that my english is not the best, but I hope I can explain myself comprehensible.

My car ist a 1987 Chevy Caprice 305 with H-Code engine. Electronic 4BBL and catalytic converter.

Everytime I start the car, after 5 -10 minutes the temperature gauge is going up to 120°C / 240 - 250°F.
Then the thermostat opens and the gauge is going back to 100 - 105°C / 210 - 220°F

But this can´t be right, the car doesnt overheat and runs very smooth.I´ve bought an infrared thermometer and the radiator hose is not warmer than 75°C / 170°F.

I have checked:

1. Cylinder head gasket ok. No Co2 in the coolant water and no white smoke from the exhaust.
2. No Air in the coolant system.
3. Changed the thermostat two times.
4. Changed the coolant water sensor.*
5. Checked the heat exchanger, ok
6. Checked the visco fan, ok
7. Checked the catalyst converter, ok
8. No leak in the coolant system

*I hope I have changed the right sensor. I´m not sure about the right location of the coolant water sensor for the gauge.
Is the sensor located on the side of the exhaust manifold, or is it the one in the thermostat housing?

So, I absolutely don't know what esle I can do to fix the problem.
has anyone an idea?

Thank you very much for your help! Tom

This is how it looks like:

chevymetal

Done... I fixed it!

The coolant sensor was delivered broken.
(2 times!!!)