1. Leakage from the mounting surface
Appearance: Seepage, drips or large coolant bleed marks on or around the mounting surface or on the housing.
Cause: Improper thermostat installation or improper use of seals/gaskets or sealant.
Solution: In case of a recently installed new thermostat: carefully remove, check and re-install the thermostat. Strictly follow the torque specifications. Make sure seals/gaskets are in perfect condition and are installed correctly. When sealant is prescribed, clean the rims of the part and the mounting surface and apply new sealant evenly along the edge of the part. If the leakage is not the consequence of an improperly installed new thermostat, the thermostat must be replaced immediately.