If you're fortunate to own a 2000 Volkswagen Jetta with a 2.0-liter engine you know how peppy it is. You have likely modified your engine with power adders like a high flow cold air intake or a larger free flowing exhaust. These add on parts will make your Jetta run faster but it only takes one low cost part to bring your Jetta to a halt. Routine repairs like replacing a broken thermostat should not be overlooked because it is the simple things that can scrap an engine.
Remove the thermostat housing from the intake manifold by removing the two bolts that hold it in place. The thermostat is under the housing. Pull up on the thermostat housing and hold the radiator hose vertical to push the coolant back into the radiator. Push the hose and the housing off to the side to access the thermostat.
Lift the thermostat out of the Jetta's intake manifold and discard it. The old thermostat will not be use again. Plug the hole in the intake manifold with a shop towel.
Scrape the old gasket material off of the machined surface on the intake manifold. Do not get any of the gasket into the intake. If this happens, the intake must be professionally flushed to prevent the silicone from blocking critical engine veins that move the fluid through the engine. Once the gasket has been scraped off brush the intake off to remove any excess gasket pieces.
Pull the shop towel out of the intake and place the new thermostat into the hole. It will sit on a machined lip that is located inside of the intake. The lip may be hidden by coolant fluid.
Place a small amount of RTV silicone around the hole on the machined surface of the intake. Allow the RTV silicone to cure for 15 minutes before moving on. This will allow the RTV to "skin over" and promote a better seal between the thermostat housing and the intake manifold.
Place the thermostat housing back onto the intake manifold and bolt it into place. Start the engine and check for leaks. If there are any leaks, slowly tighten down the thermostat housing until the leaks stop.
