Another temp issue on a 67 GS 400

Sorry for this post but I am at a loss. I am sure you all are tired of overheating issues.

My temp gauge shoots up to 230 degrees at idle and back down just as quick when I rev to 2500 rpms in neutral. New coolent, hoses, belts, thermostat........the fan seems fine and I do have the stock shroud.

I installed a new temp gauge and both gauges behave the same so my gauge is not the problem. Tried to get the air out of the system by having the car on an incline running for 20 minutes with the rad cap off but that didn't work. I feel like I still have air in the system. Car seems fine running 35 to 55. Mph but the gauge shoots up to 230 when slowing down or at idle. The temp rises quick and drops quick.

Any sure fire methods to remove air from the cooling system? I want to eliminate that as an issue first.

400 motor with a/c. Stock fan and shroud. Problem began after I replaced the timing cover and gasket.

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Originally Posted by Shakadula51

Sorry for this post but I am at a loss. I am sure you all are tired of overheating issues.

My temp gauge shoots up to 230 degrees at idle and back down just as quick when I rev to 2500 rpms in neutral. New coolent, hoses, belts, thermostat........the fan seems fine and I do have the stock shroud.

I installed a new temp gauge and both gauges behave the same so my gauge is not the problem. Tried to get the air out of the system by having the car on an incline running for 20 minutes with the rad cap off but that didn't work. I feel like I still have air in the system. Car seems fine running 35 to 55. Mph but the gauge shoots up to 230 when slowing down or at idle. The temp rises quick and drops quick.

Any sure fire methods to remove air from the cooling system? I want to eliminate that as an issue first.

400 motor with a/c. Stock fan and shroud. Problem began after I replaced the timing cover and gasket.

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The last sentence should be a clue. Extra rpm needed to cool would be one of two things: poor water pump performance / poor circulation, or airflow across radiator.

Was the front cover an EXACT replacement and is the water pump impellor clearance correct? Always suspect the last thing you did before the problem showed up.

My new thermostat was bad. Put in a new 180 and the temp is stable. Only jumps about 5 to 10 degrees at idle but stays below 200. I'm happy with that.

Thanks for your help.