1988 Jeep Comanche Thermostat Installation Instructions

The thermostat on a 1988 Jeep Comanche consists of a temperature-sensitive valve at the upper radiator-hose housing on the engine. When cool, the valve is closed, allowing the engine to warm to operating temperature more quickly. As engine temperature increases, the valve opens, allowing engine coolant to flow through the radiator where it is cooled. A defective thermostat might result in engine overheating or an engine that is slow to warm to normal operating temperature. The thermostat is not repairable and must be replaced if defective. No specialized tools are required.

Tools Used: RTV sealant. Socket wrench set. Flat-blade screwdriver or gasket scraper. 1 gallon antifreeze coolant.

Install Thermostat

Remove old thermostat.

Remove the two bolts from the thermostat housing, using the appropriate size socket and ratchet.

Pull forward on the thermostat housing to remove it from the cylinder head. Remove the thermostat from the cylinder head if it did not come off with the housing.

Remove all old gasket material from the mating surfaces of the thermostat housing and cylinder head, using a gasket scraper or flat-blade screwdriver. Be sure both surfaces are clean and dry prior to reassembly.

Install new thermostat.

Apply a 1/8-inch bead of RTV sealant around the mating surface of the thermostat housing, circling the bolt holes.

Position the new thermostat in the opening on the cylinder head and install the housing over it. Install the housing bolts finger tight.

Tighten the thermostat housing bolts securely, using a ratchet and socket. Wait a few hours for the RTV sealant to cure.

Start the engine and allow it to reach operating temperature. Shut off the engine and allow it to cool completely.

Check the coolant level and add coolant as needed.

Tips & Warnings

Never open any part of the cooling system when the engine is hot. Hot coolant is under pressure, and doing so may cause injury and damage to the vehicle.

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