An oil filter housing is the location where the oil filter sits in a vehicle engine. Frequently, when an oil leak develops, the cause is a problem with the gasket in the housing.
Troubleshooting an oil leak begins with loosening the housing lid until the mechanic can see the O-ring that forms a seal and letting the oil drain into the pan. Then the mechanic unclips the upper radiator hose retainer, takes the hose from the housing, and lets the coolant drain into a suitable container.
Disconnecting the sensor electrical connector and taking the housing fastener off give the mechanic access to the housing. Cleaning the surface of the housing and replacing the gasket, if worn, complete the repair process.