The Suburban 2500 is a large, full-sized SUV capable of towing large payloads. With this ability comes a dependency on an efficient cooling system. The weakest point of the cooling system is the mechanical thermostat located inside of the intake manifold. When the engine is under stress, it forces the thermostat to work in a manner that is stressful for the spring inside the thermostat. When the spring in the thermostat fails the Suburban overheats and then the thermostat must be replaced.
The engine must be cool. Loosen the radiator cap to relieve any pressure in the cooling system. Trace the upper radiator hose from the radiator to where the hose connects to the engine. The metal part that the hose connects to is the thermostat intake housing.
Remove the hose from the thermostat intake housing by loosening the retaining band that secures the hose. To do this, pinch the two clips that protrude from the band together with pliers. This loosens the pressure on the hose. With the clips pinched together, pull the hose off the housing. If the hose has a screw-type hose clamp, simply unscrew the knuckle until the clamp is loose enough to slide it down the hose and out of the way. With the hose loose, lift the loose end into the air to drain any fluid in the hose into the radiator.
Remove the two bolts that hold the thermostat onto the intake manifold with a wrench. Turn the bolts counterclockwise to remove them. Lift the thermostat intake housing off the intake manifold. You may have to pry it loose with the screwdriver.
Remove the thermostat by lifting it out of the intake manifold and replace it with the new thermostat. Place the end with the spring on it into the intake manifold. This ensures proper orientation.
Lift the old thermostat gasket off the machined surface of the intake manifold and put the new one in place. If the gasket doesn't come off in one piece, scrape both mating surfaces with a scraper or flat-bladed screwdriver until both surfaces are clean.
Place the thermostat intake housing back on to the intake manifold and bolt it down using the existing bolts.
Pinch the tabs of the radiator hose band and slide the hose back onto the thermostat intake housing. Release the tabs to secure the hose into place.
Top the radiator off with coolant. After running the engine to operating temperature and letting it cool again, check the coolant level again--more may be needed to replace the air that has worked its way out of the system.
