Dorman 902-103 Engine Coolant Thermostat Housing - Lower

Engine Coolant Thermostat Housing for S10 and Sonoma

Dorman 902-103 is a replacement engine coolant thermostat housing built to match the fit and durability of the original housing on specified vehicles. It is made for lower cooling system applications on 1998-2003 Chevrolet S10 and 1998-2003 GMC Sonoma models, with materials selected to handle repeated temperature swings.

• Direct replacement engine coolant thermostat housing for specified applications
• Aluminum and steel construction with black and silver finish
• Includes gasket and seal components for the housing assembly
• 45-degree housing neck angle
• Five mounting holes with 0.36 in. mounting hole diameter
• Outlet port diameter: 0.757 in.
• O-rings included; thermostat not included
• Package contents: coolant adapter pipe, housing gasket, thermostat gasket, ignition wire holder

Detailed Application Coverage

This Dorman 902-103 thermostat housing is engineered for lower cooling system service on the Chevrolet S10 and GMC Sonoma. It is a practical OE-style replacement for vehicles that need a new coolant thermostat housing, especially when the original housing has corrosion, cracking, or sealing wear. This part cross-references Dayco 85017 for the same application.

Compatible With 1998-2003 Chevrolet S10, lower; cover, adapter, w/pipe. Compatible With 1998-2003 GMC Sonoma, lower; cover, adapter, w/pipe.

Common Problems This Part Can Address

• Coolant leaks at the thermostat housing or gasket surface
• Cracked or warped housing from heat cycling
• Corrosion or deterioration in the coolant outlet area
• Improper sealing at the lower thermostat housing connection
• Service issues caused by a damaged adapter pipe or housing neck

Installation Notes and Tips

Verify the lower housing location, outlet port size, and 45-degree neck angle before installation. Clean the mating surfaces thoroughly and inspect the coolant passages for residue or scale before fitting the new gasket and O-rings. This housing does not include a thermostat or bolts, so reuse or source those components as needed for the repair.

Quality Assurance

Dorman designs this replacement housing to match the fit and durability of the stock thermostat housing on the listed Chevrolet S10 and GMC Sonoma applications. The aluminum and steel construction is selected to withstand extreme temperature changes and support long service life in cooling system use.