Thermostat Position

[Dave G]

Drilled and tapped boss on thermostat housing for temp gauge sensor.  Sensor plug contacts thermostat.  Honda shop manual says thermostat should be installed with small hole toward the rear.  What is the hole for? If I rotate the thermostat the sensor plug will fit. Rotate or do not rotate?

[turtle254]

Drilled and tapped boss on thermostat housing for temp gauge sensor.  Sensor plug contacts thermostat.  Honda shop manual says thermostat should be installed with small hole toward the rear.  What is the hole for? If I rotate the thermostat the sensor plug will fit. Rotate or do not rotate?

What is the hole for?

To allow some water past the thermostat to get a true reading on the water temperature

[sandy]

Go ahead and rotate it. The bleed hole position isn’t important when the ‘stat is horizontal. If it were vertical, the hole should be at the top.

[Avanti]

I put a sensor in mine way back. Thermostat will only go in clocked slightly to miss the sensor. Never a problem.

I also as of lately have use the Gates PowerGrip Thermoplastic Hose Clamps which look nice  and work well.

[Crusty1]

Drilled and tapped boss on thermostat housing for temp gauge sensor.  Sensor plug contacts thermostat.  Honda shop manual says thermostat should be installed with small hole toward the rear.  What is the hole for? If I rotate the thermostat the sensor plug will fit. Rotate or do not rotate?

What is the hole for?

To allow some water past the thermostat to get a true reading on the water temperature

The small hole is a bleed hole to prevent air pockets from forming under the thermostat.  An air pocket would prevent the thermostat from opening and cause overheating.  In a car where the thermostat is mounted vertically the hole goes to the top.