Engine temperature rises at a idle.

89 Buick Century replace the bad intake manifold gasket and thermostat(195) have put over 5000 miles on it after replacing the manifold gasket. But after replacing the gasket the temperature will start to climb after 3 to 4 minute at a idle(traffic light) before the cooling fans start and then the temperature will drop down. Driving the temperature stay at a constant. Is this normal or is there a sensor going bad? Engine has never overheated.

I check the thermostat before installing, used very little RTV ( rebuild few 100 engines in my time know what RTV can do) and i rechecked the coolant level and rebleed the cooling system. Still having the same problem.

Mike

A couple possibilities:

1-air pocket/low coolant

2-improper 'stat operation, yes even if its' new. Nice way to check em before you install em? Pot of water on the stove.

3-a piece of RTV blocking the water neck.

I lean towards #1 tho. :2cents: