Dorman 902-5019 Engine Coolant Thermostat Housing - Upper

Engine Coolant Thermostat Housing for Mazda

Dorman 902-5019 is a replacement engine coolant thermostat housing built to match the fit and durability of the original housing on specified vehicles. It is made from metal and includes a gasket for a direct cooling system service on select Mazda 323, Protege, and MX-3 applications.

Compatible With 1990-1995 Mazda 323, upper; 1990-1994 Mazda Protege, upper; and 1992-1993 Mazda MX-3, upper. This thermostat housing is shaped for the upper cooling circuit and uses a 15-degree housing neck angle to match the factory layout.

Key Features

• Metal construction for strength and heat resistance
• Natural finish
• Outlet port diameter: 1.188 in.
• Two mounting holes with 0.313 in. diameter
• Gasket included
• No thermostat included
• No bleeder valve
• Package contents: thermostat housing with gasket

Detailed Description

Dorman 902-5019 is engineered as a direct replacement engine coolant thermostat housing for the upper cooling system on select Mazda models. It is designed to match the stock housing’s fit and durability while handling repeated temperature swings common in engine cooling service. The metal housing and included gasket support a proper seal at the thermostat mounting point, helping restore the cooling system connection on Mazda 323, Mazda Protege, and Mazda MX-3 vehicles.

This part cross-references Dayco 85021 and Valeo 815529 for the same application. If you are replacing a worn or corroded thermostat housing on a 1990-1995 Mazda 323, 1990-1994 Mazda Protege, or 1992-1993 Mazda MX-3, Dorman 902-5019 provides the correct upper housing configuration.

Common Problems This Part Can Address

• Coolant seepage at the thermostat housing flange
• Corrosion or cracking in the original metal housing
• Improper sealing at the upper cooling system connection
• Fitment issues caused by a damaged factory housing neck
• Service replacement for a worn thermostat housing on Mazda cooling systems

Installation Notes and Tips

Confirm the upper housing position, outlet port diameter, and 15-degree neck angle before installation. Clean the mating surface thoroughly before fitting the included gasket, and inspect the thermostat separately since it is not included. Verify that the mounting hole spacing and diameter match the original part on your Mazda 323, Protege, or MX-3.

Quality Assurance

Dorman designs this replacement thermostat housing to match stock fit and durability and to withstand extreme temperature changes for extended service life. Use it as a direct replacement for the specified Mazda cooling system applications.